Howto: PLC Reef Controller II

[gabe21804]

Well needless to say the other thread was closed. Rather than try an argue that we were not in the wrong, and there was no illegal activities, ill just start a second thread.

Please in this second thread do not mention the word "SOFTWARE" and refer to all programming and coding as generic ladder logic. Ill give this a second and final shot, if something happens again I'll find a fourm site that will take this project.

For anyone who wishes to catch up in both of the other threads here they are.

http://www.reefcentral.com/forums/showthread.php?s=&threadid=529880

http://www.reefcentral.com/forums/showthread.php?s=&threadid=535018


Respectfully Submitted,

[easttn]

Wow, never intended to start such a commotion. Sorry all.

[eleben]

Can't wait to get started in developing the code for my own tank. Just waiting on my plc (Siemens) shipment from Easttn. If all goes well I would like to try out one of the ezautomation plc's (as someone else suggested) to compare the two. I'm a college student but it is very beneficial to do some testing for this hobby even if it means spending some hard earned money.

[gabe21804]

Originally posted by eleben
Can't wait to get started in developing the code for my own tank. Just waiting on my plc (Siemens) shipment from Easttn. If all goes well I would like to try out one of the ezautomation plc's (as someone else suggested) to compare the two. I'm a college student but it is very beneficial to do some testing for this hobby even if it means spending some hard earned money.

I'd love to see someone purchase a automation direct plc or a ezplc, just to see how it goes. Most of this stuff can be converted between brands with ease.

[eleben]

Sure now you tell me. lol. I would have tried the EZplc out. The main concern I have is getting a pH meter interfaced with the PLC. That is what I would like to see happen - I know they use them in industry for water quality tests but I haven't noticed any DIY pH controllers combined with a PLC yet. (If there are any that are setup and have pictures/diagrams I would love to see them) I know you (gabe21804) is working on getting his setup done - but it would be nice to see how everything interfaces together in a "final product"

[javajaws]

Originally posted by gabe21804
I'd love to see someone purchase a automation direct plc or a ezplc, just to see how it goes. Most of this stuff can be converted between brands with ease.


Glab this topic has been resurrected.

I'll be buying either a EzPLC or a DL06 here in the next couple of days. The only thing I'm hesitant about on the ezplc is that no one else here or elsewhere has much experience with it so I won't have much of a place to go for questions. It'll probably be the DL06 for that reason...

- Jason

[javajaws]

Originally posted by eleben
Sure now you tell me. lol. I would have tried the EZplc out. The main concern I have is getting a pH meter interfaced with the PLC. That is what I would like to see happen - I know they use them in industry for water quality tests but I haven't noticed any DIY pH controllers combined with a PLC yet. (If there are any that are setup and have pictures/diagrams I would love to see them) I know you (gabe21804) is working on getting his setup done - but it would be nice to see how everything interfaces together in a "final product"

Well, on the PLC side of things you need a 4-20 mA analog input. Connected to that is a transmitter which outputs the 4-20mA signal. Connected to the other side of the transmitter is the pH (or ORP) probe. If you would like to know how to take the 4-20 mA signal and turn it into a pH value I'd suggest you look at the AD DL06 manual (or your PLCs manual)...AD has great easy to understand documentation on how this stuff works (specific for the DL06 but the concept is the same for other PLCs). Here's the relevant DL06 documentation...especially check out pages 11 and 12 on scaling raw data values...

http://web2.automationdirect.com/static/manuals/d0optionsm/ch3.pdf

- Jason

[javajaws]

Has anybody thought about using a PID loop for controlling temp, etc.? Or is that overkill?

[eleben]

javajaws - Thanks for the info!!!

David

[javajaws]

OK, one more question: How do you calibrate a pH probe...by adjusting the transmitter or something in the PLC?

[javajaws]

I hate it when I answer my own question...from http://www.automatedaquariums.com/h_8614.htm:

"Calibration is performed with one or two trimmers for offset and slope adjustments"

[eleben]

Anyone know of a cheaper source for a pH transmitter. I was just searching for one and there are many available it is just that all of them are easily over $100 just for the transmitter and no probe.

Thanks,
David

[inerratum]

I think gabe has a schematic for a ph transmitter that he is going to try to build, with anyluck it will work and be a big money saver. If not there are some probes that have a built in transmitter but with probes having to be replaced every so often means your paying extra for the built in transmitter each time.

[eleben]

I thought I remembered him talking about the schematic for a pH transmitter. I am definitely on board to get this going. I have an Co-op with Kimberly Clark coming up in June and my tank is at my parents house. I won't be coming home every couple weekends like I do know to take care of my tank so I need to get things running as best as I can so my parents only have to do a little maintenance here and there while I'm gone. pH is a big concern of mine since my tank has such a low pH problem and don't really have any good way of measuring it yet. I bought a Hanna pH meter but I haven't had the best of luck with it. Anyways...I digress back to PLC talk

[gabe21804]

Originally posted by eleben
Sure now you tell me. lol. I would have tried the EZplc out. The main concern I have is getting a pH meter interfaced with the PLC. That is what I would like to see happen - I know they use them in industry for water quality tests but I haven't noticed any DIY pH controllers combined with a PLC yet. (If there are any that are setup and have pictures/diagrams I would love to see them) I know you (gabe21804) is working on getting his setup done - but it would be nice to see how everything interfaces together in a "final product"

I just now started to think of the big picture ;) ...We need to be looking at a setup that can be purchased by anyone, and not just someone waiting for parts to appear on a auction site.

Automation Direct Stuff is going to get pricey quick, I think I priced a setup with everything you'd need at $650 with the dl06 as the base.

The ezplc could be the golden ticket, someone just needs to purchase a unit and be the test subject. Or try and write a real good email and get a free sample unit, some companies will send you a sample if you can prove it will benefit them.

As for the ph/orp....etc interfaces I have a schematic of a ph transmitter with a calibration circuit built into, parts are roughly $40-$60 I'm guessing, I'm going to suck up the cost and see if I can't get something working, this may save a ton of us some cash. I can't afford to drop $150 on just the transmitter.

Law: By any chance did you take a look at the code I gave you? If so did you figure out whats wrong with it? Mainly Im trying to use that as a base to datalog from 8 different byte addresses, save the addresses and plot them on a graph. I'd like it to resemble something you see in a control room in a manufacturing plant, that shows the pictures of the pipes on the monitor and which valve is closed...etc but instead of valves the graphs for the probes...

I can figure out the gui part, its just getting that link to the plc that I'm having the problem.

[eleben]

Gabe21804 - If you want I would be willing to purchase the EZPLC for testing purposes. I just need to know what I need to purchase - what you think we would need to get this off the ground. Send me the list and I will see what I can do. Also if you want I will send you 1/2 of what it costs to get the parts needed for the pH transmitter.

Thanks,
David

[javajaws]

I can tell you what you need for the ezplc...but you'll have to make the call on which base PLC unit to get...the one with 4 expansions slots, or 6 (or more). I think 4 may not be enough because you'll have to use 1 for the analog IO and 1 for the thermocouple IO...leaving you with only 2 slots open (8 in and 8 out probably). The 6 expansion unit will probably be better. I'll post later tonight with a shopping list if you're interested.

- Jason

[eleben]

Sounds good. Just try to do a basics to get things started but of course leave room for expandability.

Thanks,
David

[gabe21804]

Originally posted by eleben
Gabe21804 - If you want I would be willing to purchase the EZPLC for testing purposes. I just need to know what I need to purchase - what you think we would need to get this off the ground. Send me the list and I will see what I can do. Also if you want I will send you 1/2 of what it costs to get the parts needed for the pH transmitter.

Thanks,
David

I'd get the programming cable, the evil S word ;) thats banned from this thread, and the plc, and thats it for now. Don't spend anymore than that intial plc portion til we figure out what this thing is capable of. If it looks like it works I'd then look into getting modules. Let me take a look at the specs of the units and see which one looks like your best bet, the issue that may arise is the lenght of code that can be programmed into the units. I complex setup code have an extremely long code length.

Ill let you know when I attempt this ph transmitter, its on hold for the next week or so, still have no clue whats going on with me.

[gabe21804]

Eleben:

I'd get the EZPLC-A32

If you feel youll go over 32 inputs and outputs I splurge for the EZPLC-A48....that choice is on you. Ethernet looks extremely intresting considering its built right on, I'm not that far in my project yet, so that choice would also have to be on you.

From what I'm seeing the rs232 port can be used as a programming interface and a HMI interface (AKA LCD screen..etc), I'm not sure if its possible to link back to a computer with this port on this particular product this would require more research. Although the ethernet port looks like its a direct link that can be used to monitor it. If you can afford it and your not hurting yourself I'd say go for the ethernet if not we can work around this, an ethernet module for my plc costs entirlely too much new or used for me to look into it at the moment. As I said I'm trying to keep the cost down as much as possible, if we can get this up and running not just on mine but someone with something you can buy easily it may make this project more attractive.

Also for now I'd just get one Digital DC Input and output, this will allow you to use 24VDC relays to trigger your high voltage stuff which will be cheaper than using the ezplc relay module.

Get the programming cable, and the evil S word.

Hold off on the analog i/o module til we get to that step in the project and have the rest of your setup working.

So right now your looking at this.

EZPLC-A32 ($129) or EZPLC-A48($168) or you can opt for the ethernet option thats your decsion.

Digital DC Input Module ($19)

Digital DC Output Module ($19)

Programming Cable ($30)

Evil S Word ($49)

Thats all you'll need to figure this unit out, you can purchase additional modules once you've got the basics running.

[javajaws]

Originally posted by gabe21804
Let me take a look at the specs of the units and see which one looks like your best bet, the issue that may arise is the lenght of code that can be programmed into the units. I complex setup code have an extremely long code length.


All the EZPLC units have 64KB total memory (which I believe is relatively a lot and more than a DL06). FYI, here is a link to the EZPLC online downloadable docs:

http://www.ezautomation.net/downloads/docs/docs.php

[gabe21804]

Originally posted by javajaws
All the EZPLC units have 64KB total memory (which I believe is relatively a lot and more than a DL06). FYI, here is a link to the EZPLC online downloadable docs:

http://www.ezautomation.net/downloads/docs/docs.php

Yeah I noticed the memory thing when I looked at the features list.....

Wow looked over the programming manual, for the most part it looks like you could translate my code for the s7 line for line into this thing.

[javajaws]

OK, I did a price check for nearly identical EZPLC and DL06 setups (identical enough to meet our needs). Here first are the numbers:

EZPLC-D-48 (6 slot PLC base, AC power) 168
EZPLC-EDIT (Software) 49
EZPLC-BAT (Backup Battery) 20
EZP-PGMCBL (Programming Cable) 20
EZIO-8DCI (8 DC inputs) 19
EZIO-8DCI (8 DC inputs) 19
EZIO-8DCON (8 DC sinking outputs) 19
EZIO-8DCON (8 DC sinking outputs) 19
EZIO-8ANIC (8 ch 4-20 mA analog input) 99
EZIO-4THI (4 ch Thermocouple input) 139

Total: $571


D0-06DD1 (PLC) 199
PC-PGM_BRICK (Software) 149
D2-BAT-1 (Backup Battery) 12
D2-DSCBL (Programming Cable) 30
F0-04AD-1 (4 ch 4-20 mA analog input) 79
F0-04THM (4 ch Thermocouple input) 199

Total: $668


So for our configs...the only real significant savings with the EZPLC comes from the software cost and the cost of the thermocouple input. Given the relatively close cost (when all things are considered...counting probes, transmitters, wiring, etc.) I don't think I can personally rule out the DL06 based on price alone....$100 isn't a big deal to me.


A few comments:

Ethernet can be added at a later date to the DL06 ($175 option module). Ethernet for the EZPLC has to be ordered with the base ($99, can't add at a later date though).

The DL06 has a nifty 2-line LCD display available for $69 (mounts on the front of the PLC). It can display memory variables as well as text on each line (for displaying temp/ph/etc.). It also has some buttons for navigating and changing setpoints, etc. (I presume).

Both units can utilize external displays such as EzText.

With this configuration, the DL06 would have 2 option slots available for future expansion (1 if you add the Ethernet module). The EZPLC would be maxed out.

I'm not sure if the EZPLC supports PID loops...the DL06 includes support for 8.

The DL06 has a much larger instruction set compared to the EZPLC...could make programmability an issue. Probably not a big deal for our relatively simple needs though.

The DL06 has an RTD input module available, the EZPLC does not (as of yet).

The DL06 has a relatively large user base and help can easily be found from outside resources. The EZPLC is new and does not have a large user base as of yet.

AutomationDirect technical support is supposed to be pretty good, haven't heard anything about EZPLC yet.


So I'm personally leaning more to the proven product that has been around the block...the DL06. I just don't know if saving $100 is worth it in the long run to go with the EZPLC.

- Jason

[eleben]

JavaJaws I'm with you on this one. However, I think I will still tryout the EZPLC just so that we can get a comparison of everything. They do have a 30day return policy. I do like the overall quality of the AutomationDirect PLC (bias based on pictures only - not based on actual use). One of the only problems I have with the EZPLC is the fact that the ethernet has to be purchased now instead of it being an actual module. I do like the idea of remote monitoring and exporting it to computer using ethernet instead of the RS232 port.


One thing I do like about the EZPLC is the fact that the I/O are just modules that are removable and easily replaced with other (cheap $$$) modules if needed.

[inerratum]

I think is a good idea to try different plcs to see what we can do. Im having a rally hard time finding the siemens stuff that I need, cant even seem to find the programming cable for a reasonable price.

[javajaws]

I went ahead and bought the DL06 this morning. Got everything (including the LCD display) except the thermocouple unit...I'll add that later ($$).

BTW, 2 other things to consider:

The AC powered version of the DL06 has an auxilliary 24v power supply (300mA). This will help power some external relay circuits, a pH transmitter, etc.

The software for the DL06 seems more full featured than that of the EZPLC. I've downloaded demo versions of both and believe DirectSoft has way more features. Both pieces of software leave something to be desired in the usability department though (I'm a harsh critic though since I write developer tools for a living).

[eleben]

Did you get the D0-06AR, D0-06AA, or the DC version?

[javajaws]

D0-06DD1 (AC power DC in/out) - I plan on using it to power a relay bank. I didn't want to go with the internal relays because I wanted to use higher amp relays and thought I'd save the extra $30. I think I'll get something like the Ziplink 8-ch relay connector module (p/n ZL-CM08RL24) later for this.

[gabe21804]

Just a thought a 300ma 24v powersupply is extremely minimal. I bank of relays may come close to drawing 300ma's depending on what type they are and how many, relays do draw current, and no powersupply is 100% efficent.

In my situation I had to opt for a external 12vdc 2.5amp powersupply to run my fans, leds, and relays. I used one that has a 120 hardwired input instead of a plug in, I hate plug in transformers especially in a clean setup. In our world 24vdc wouln't run much other than a relay. On the other hand 12vdc can run cheap fans, you can run your float switch with 12vdc instead of 24vdc or 120vac, with a few resistors you can have a array of leds that simulates sunrise and sunset, and moonlight.

I'm extremely happy with my s7 setup, its not new but I think the total I'm at right now with everything electrical is $275.

[inerratum]

Hi gabe, I was wondering if you could take a close up pic of the analog and thermocouple module, preferably with the covers open. I want to try to draw up a diagram of all the wiring but I dont know what the inputs are on those 2 modules and how they need to be wired to transmitters etc.

Thanks, if its too much trouble please dont bother.

[eleben]

Eastn - I just wanted to give you a quick thanks for sending me the S7-200 CPU 224 Siemens PLC and the extra I/O module! It looks great - I just need to get the cable now.

[eleben]

Is the Siemens cable just a converter from RS485 to RS232 or is it more involved than that?

[eleben]

Never mind I answered my own question! Of course it isn't. I think I will be selling the Siemens PLC 224 and I/O module if I can't find the cable in a reasonable amount of time.

[gabe21804]

Originally posted by BlitzM4
Hi gabe, I was wondering if you could take a close up pic of the analog and thermocouple module, preferably with the covers open. I want to try to draw up a diagram of all the wiring but I dont know what the inputs are on those 2 modules and how they need to be wired to transmitters etc.

Thanks, if its too much trouble please dont bother.

Ill post something later today.

[slug]

I've attepmted a couple different circuits to make high impedence signals readable by my automated system. I'm not an EE but I'm not entirely electronically challeng either and I can't get any of them to work. I can't see paying $250-300 for one of the transmitters listed here. The last circuit I tried was the one listed on barebottoms site with a max406 chip. Has anyone gotten this working?

I can turn relays on all day long but a system like this is a lot more usefull with inputs like ph/orp/conductivity. At least temp is easy.

[gabe21804]

Originally posted by slug
I've attepmted a couple different circuits to make high impedence signals readable by my automated system. I'm not an EE but I'm not entirely electronically challeng either and I can't get any of them to work. I can't see paying $250-300 for one of the transmitters listed here. The last circuit I tried was the one listed on barebottoms site with a max406 chip. Has anyone gotten this working?

I can turn relays on all day long but a system like this is a lot more usefull with inputs like ph/orp/conductivity. At least temp is easy.

I've got a couple of circuits I'm going to try, before I make them I'm trying to grasp the full concept at every level of whats going on. I know basic electronics as far as what all the components do, but when I start sticking them together thats where I start to lose it, I just don't want to copy a schematic. I want to know and understand how it works before It gets built so I'm not wasting money when the the thing doesn't work.

On another note, that was one of the simpler ones I was going to try, I have a few others I found floating around google. One has builtin calibration and tempature compensation. I'm not really concerned about the tempature compensation because that can be done at the software level on the plc. The calibration is a must have, but this could also be done at the software level from what I've determined its just going to be some work.

This is by far the hardest component of this project, next to this is getting the communication link between the plc and the pc down.

[barebottoms]

Originally posted by slug
The last circuit I tried was the one listed on barebottoms site with a max406 chip. Has anyone gotten this working?


Slug, what seems to be the problem with it? Are you getting a voltage out of the op-amp?

Honestly I've been way too busy with work to try it myself, but the good news is that if there is enough interest, one of the 1-Wire boards makers might make a driver for us. I've already sent him a pH probe to play with. Maybe if I can get a count of how many people are interested in how many drivers we can motivate him even more.

[slug]

Yeah I get a voltage out, but it doesn't change with ph. I'll recheck my layout and report more specifics. The +3v in lines get hot, kinda seems like something is shorted, but it's such a simple circuit kinda hard to screw up.

[gabe21804]

Here's the schematic I'm planning on using to build a prototype amplifier for a ph probe for the plc's a/i.

http://www.web-ee.com/Schematics/pH%20Meter/ph.htm1.gif

Full explanation is at the following site, this seems to be the perfect circuit for what were doing with the plc's. I think this is the most straightforward circuit I've seen, and its nice to have an explanation with something for once.

http://www.web-ee.com/Schematics/pH%20Meter/ph.htm

[gabe21804]

I got the lmc6001, lmc6041, and the lm4040DIZ-2.5 as samples from National, they were shipped overnight for free. I've always seen resistors that were labeled with there wattage levels and ohm values. What wattage level does this circuit require, also what style of resistor are we talking about?

Worst comes to worst, I've got almost nothing invested in this, the only thing I'll have to buy are the resistors; te opamps, and diode are samples. As for the probe, I'm thinking about using a pinpoint replacement probe, due to the fact there extremely cheap ($44).

If someone wants to help me out with the digikey part #'s for all the resistors and the tempature compensating resistors, I'd love the help its a pain to sit down and come up with all the part #'s in digikeys catalog.

[slug]

Wattage values on resistors tells you the max they are rated for and this is a low wattage circuit so any wattage value should be ok.

I have the chips for that circuit too, but R1 is hard to find.

[gabe21804]

Originally posted by slug
Wattage values on resistors tells you the max they are rated for and this is a low wattage circuit so any wattage value should be ok.

I have the chips for that circuit too, but R1 is hard to find.

Did you find R1? I've looked with no luck...

Also R3, and R4.

R3 looks like it says 8 5k,
is this 85k or eight 5k resistors? which would be 40k? I'm lost here.

Same with R4 it says 9 100k, is this 9100k(9.1M), or 9 100k resistors 900k?

[inerratum]

I know this is a little off topic but does anyone know the equation (if there is one) used to find the phase of the moon on a given night?

[barebottoms]

The easy simplified way would be to choose a given day to be a new moon, then increment 29.5 days to be another new moon. 14.8 would be a Full Moon. You can scale from there.

The more accurate and compliated way is available on the net. Search google for "pom moon source code" you'll see several C and Java examples.

[gabe21804]

Well I've gotten what I need to know as far as ph and orp go. This ph circuit should work flawlessly, I'm removing the tempature compensation resistor (Its pricey and hard to find, micro-ohm has it as a special order item). I'm going to replace it with a 100k resistor, and use a thermocoupler next to the ph probe, and do the tempature compensation in the plc's program. The only problem I forsee is our MH's I'm going to have to put sometype of capacitor on the + and - feeds into the circuit in order to filter out the noise. I've read a few articles regarding MH's and other ballast type lights throwing off readings on these diy circuits, I'll test this when I build it.

I'm going to order both a ph probe and orp probe (I have no need for orp readings but I'm going to get a probe in order to test a second circuit for orp readings). Considering ORP stays in MV's and doesn't have to be converted into another type of measurement this should be a simple opamp circuit.

I've ordered enough parts for 2 intial circuits. For those of you who are monitoring this thread getting ideas for your own controllers, it would not be hard at all to modify this circuit for use on a basicx stamp / pic or some other type of microcontroller. Nor would it be hard to create a simple LCD display to show you orp values and ph values, instead of connecting it to a PLC.

Bear with me, its hard switching back and forth between normal wiring diagrams that I'm use to, to electronic schematics.

[eleben]

I know a lot of people are having a hard time (including myself) locating the cables needed to connect the PLC to a PC but I think I have found a good source on eBay. As stated in his auction...he makes them one by one and tests them. Anyways here is the auction for the cable...http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=11809&item=7500393498

Hope that helps everyone!

Thanks,
David

[easttn]

Here is a simple solution that attaches a pH probe to a high-impedance input of an op amp. The output is then read to the input of a digital voltmeter(Fig1). I used LFXXX rather than LMXXX for the JFET Op Amps, $4.50 for all all parts including caps and resistors.
http://img.photobucket.com/albums/v461/easttn/Figure1.jpg


You will still need to convert the the DMM readings to pH units using a calculator to plot three dots on the line. Figure 2 shows a typical plot of pH versus millivolt output. (Note that pH is temperature-dependent; you have to recalibrate if the temperature changes.) It is also very linear.
http://img.photobucket.com/albums/v461/easttn/Fig2.jpg

To calibrate the system use 3 pH standards, 4-, 7-, and 10-pH units. These standards are inexpensive and available at any chemical-supply house and most LFS.

The calibration procedure is as follows:

Short the input leads (pins 2 and 3) together and adjust the offset potentiometer such that the output reads 0 mV. Untie the leads. Place your pH probe in each standard and record the output (in millivolts) for each standard and record the values in your calculator and determine the slope of the line. Remember y=mx+b? :D

If you want to drive the signal directly to pH units, build this guy in FIG3:
http://img.photobucket.com/albums/v461/easttn/Fig3.jpg

At approximately 24°C, the equation for the slope of the line is Y=–0.017X+7, for better accuracy lets redo the equation by ten. We now have 10Y=–0.17X+70.

There are three sections in Figure 3. The voltage from the probe to pin 3 of LF351 provides the high-impedance input. This device inverts the signal and then outputs a signal to one-half of the LF353 to control the slope. This LF353 also multiplies the LF351's output by –0.17. The last stage uses the second half of the LF353, and it functions as a summing amplifier and controls the Y intercept by adding 70 mV to the input signal.

When you build this circuit, solder the BNC directly to the op amp's input pin to prevent any added impedance levels from the probe.

After you build this guy, its time to calibrate and set the slope. To calibrate the circuit, first short the inputs together and adjust the offset potentiometer to obtain 0-mV output from the LM351.

To calibrate the circuit for pH units, place the pH probe into a pH standard. Measure the voltage at the output of the LM351. Multiply this voltage by 0.17 and adjust the slope potentiometer until the output of the second op amp (Pin1 of the 353) is exactly the number you just calculated only negative in value. Then, connect the meter to the output of the circuit and adjust the Y-intercept potentiometer until the circuit yields the pH of the standard you use. (For example, a pH of 10.1 reads 0.101V.) To tweak the circuit, place the pH probe in other standards and adjust the Y-intercept potentiometer.

Lastly if the temperature changes, you must recalibrate, but since we don't typically deal with much temp changes this issue is moot. The accuracy of this circuit is generally ±0.1 pH units. When you order pH probes, you should order low-impedance units. This particular circuit uses Cole-Parmer (www.colepalmer.com) U-59001-65 probes.
Probe (http://www.coleparmer.com/catalog/product_view.asp?pfx=U&sku=5900165&cat=1&sel=5900165)

Now Roy, how do we do code to get the PLC to control and not just monitor?

[javajaws]

So what kind of output is that circuit putting out? +/- 600 mV? What type analog input would you need on the PLC to use this with?

[easttn]

Depends on temp, but certianly less than +/-600mV, pH will stay around the 8.0pH range. If you ever see a positive voltage your tank is reaking. The voltage output of this circuit is a direct feed to an EM235. It is basically an A/D converter type PLC with trim pots for calibration. This unit communicates to the CPU and in turn the PLC controls some event. Turn on a powerhead to supply Kalk if pH drops below 8.2 too low for example.

[javajaws]

Originally posted by easttn
Depends on temp, but certianly less than +/-1V. The voltage output of this circuit is a direct feed to an EM235. It is basically an A/D converter type PLC with trim pots for calibration. This unit communicates to the CPU and in turn the PLC controls some event. Turn on a powerhead to supply Kalk if pH drops below 8.2 too low for example. Or shunt power to Ca reactor if pH clibs over 8.4.

OK, so I assume if you use the circuit in figure 1, you would be using an analog input with a voltage (bipoler) range of +/- 1V.

If using the figure 3 circuit, I assume you would want to use a lower range if possible (+/- 100mV or 250mV).

For those not using Siemens equipment:

For a DL06, the only analog input I have found that supports a bipolar voltage input in this range is the F0-04THM (same module used to measure thermocouple inputs). The F0-04THM has multiple bipolar mV input ranges, including a +/- 156mV that should work with the circuit in Figure 3. Unfortunately, the F0-04THM can't measure both a thermouple input and a voltage input at the same time...you would need 2 of them ($200 each).

For a EZPLC, I haven't found a suitable analog input module for this.

It would be nice to have a circuit that outputs a more common 4-20 mA signal. Anybody seen one?

[easttn]

Could you use a switch and decoupling cap between the two ckts? In other words, use the switch to break the ground for both pH and Temp so only one ckt is energized at any time.

[javajaws]

Originally posted by easttn
Could you use a switch and decoupling cap between the two ckts? In other words, use the switch to break the ground for both pH and Temp so only one ckt is energized at any time.

I assume you're referring to the inability to run the pH and thermocouple off the same input module...I don't think that would work very well for a number of reasons...but the biggest being that the range has to be set via a memory setting in the PLC.

[slug]

When you order pH probes, you should order low-impedance units

Are the standard probes sold with a ph meter from some place like premiumaquatics typically low or high impedence?

[gabe21804]

Originally posted by javajaws
OK, so I assume if you use the circuit in figure 1, you would be using an analog input with a voltage (bipoler) range of +/- 1V.

If using the figure 3 circuit, I assume you would want to use a lower range if possible (+/- 100mV or 250mV).

For those not using Siemens equipment:

For a DL06, the only analog input I have found that supports a bipolar voltage input in this range is the F0-04THM (same module used to measure thermocouple inputs). The F0-04THM has multiple bipolar mV input ranges, including a +/- 156mV that should work with the circuit in Figure 3. Unfortunately, the F0-04THM can't measure both a thermouple input and a voltage input at the same time...you would need 2 of them ($200 each).

For a EZPLC, I haven't found a suitable analog input module for this.

It would be nice to have a circuit that outputs a more common 4-20 mA signal. Anybody seen one?

The problem with using a 4-20ma signal is that on the analog inputs you have to select a type for the whole module. If you use 4-20, then this is going to make it almost impossible to use a ORP probe which is simply measured in mV's and has no conversion.

The programming is simple enough, if I have a curve for the conversion or get enough data I can create one from any input, if I have values from 4, 7, and 10 thats more than enough data to create an equation on the plc to do the conversion.

[gabe21804]

Originally posted by slug
Are the standard probes sold with a ph meter from some place like premiumaquatics typically low or high impedence?

Order high impedence there cheaper, these circuits will take care of the amplifying and make the signal readable by a normal voltmeter if you wanted.

JavaJaws: Your comment about not being able to use a thermo with a ph probe on the same module is incorrect. You were right that its not possible without mod's.

You could use the same ph circuit that I posted, with a few mod's to it, it could also be used for a thermocoupler. It would output the same voltage that the ph circuit would, allowing them to both be on the same module.

Easttn: By control, do you mean use the values from the ph probe to turn outputs on and off.etc. If so thats simple each input has a varible, it'd be the same type of code that I used for the Thermocoupler module.

[javajaws]

Do any of the circuits posted so far offer accuracy better than +/- .1 pH? This doesn't seem like it would be accurate enough for our needs - I'd think we would need at least +/- .05 pH.

Also, do any of these circuits provide for any sort of isolation between input/output...or other such features to prevent noise problems?

Roy: Well, with "mods" anything is possible...knowing what the "mod" is IS the problem. In my industry (software) I'm always asked "Can you do so and so?". My answer is always: "Yep...it's only software...I can make it do anything!" :)

An analog input of either: 0-20 mA, 4-20 mA, 0-5 V, or 0-10V seems to be the most common (and cheapest) input modules available on both the DL06 and EZPLC. I'd still like to find a circuit (or a cheap prebuilt transmitter) that will output one of these outputs.

[gabe21804]

Well I'm going to attempt two circuits, .1 accuracy is fine in my opinion most handheld meters (pinpoints) are the same accuracy. Accuracy is all about how the circuit is built, if its ground and guard properly, if there is minimal to no induction into the circuit...etc

If you'd like to purchase a commercial transmitter be my guest, I'm not made of cash and can't afford $250 for a transmitter for one ph probe, I'd rather rally around $20 my cost, and deal with +/- .1 accuracy. In my opinion the circuit isn't going to flux around by .1 its going to be off by .1.

These circuits are extremely simple to build, were not even talking about double layered PCB boards for the final product. As for the thermo and the ph on the same input 0-5v's. Just sit back and look at the big picture, I think you may be looking to in-depth. Fairly soon if everyone starts using pre-made manufacture projects the cost of your controllers will surpass a commercial made project that does the same thing.

My s7 has been up and running for two weeks now doing the following.

-Monitor for leaks on the back and side glass, if the water is detected it shunts the pump and puts it into a timeout sequence. It also trips a "zone" on my home burglar alarm panel and calls the monitoring service say there is a leak on the tank.

-Monitors the sump/canopy/and main display tank temperatures. If the temp rises too high in either the display tank the halide is turned off and put into a timeout sequence. If one thermocouplers temp fluxates erratically its input is ignored in temperature decisions (it assumes it’s faulty).

-If the temp drops in the sump or tank, the heater is turned on (It has yet to have to turn on too much the mag 9 in the sump keeps the tank at a constant 80 degrees for the most part, along with the mh. When the lights turn out the heater turns on about once an hour for 5 mins it seems.

-If the temperature in the canopy rises above a certain temp, the first canopy fan is turned on; if the temp continues to rise a second fan is turned on.

-I've got push button shutoffs for every relay on the bank, if I need to turn off the MH when it’s on, I just push a 12vdc push button it sends 12vdc to an input and turns the MH off.

- Moonlights are run off an equation in the plc, depending on the day of the month, there a more or less blue leds lit.

-I have a sunrise and sunset bank of leds set on arrays that use timers and simulate sunrise and sunset.

The only things left to do are program the ph / orp code, which is simple its almost identical to the thermocoupler code.

Total Costs So Far
PLC + Modules $225
TC's $25
PH Probe $40
Materials for PH Circuit $20
Misc Relays + Elec's $25+Free
Enclosure Free

Total $335

All I'm trying to say is I intended to start this a moderate cost reef controller project, and its still possible to keep this a moderate cost project you don't have to spend tons of cash to make this possible.

[javajaws]

Roy, Please don't take my comments/questions the wrong way. My priorities are different from yours and lead me to ask questions that may not be as important to you. I am not suggesting everyone run out and buy $250 transmitters (most of these questions I am asking are so I don't have to).

MY priorities are (in order): reliability, accuracy, cost. Also thrown in there in no particular order are: usability (BNC connectors for ease in replacing probes, etc.) and the general feature set of the PLC solution (this is something only time and money can provide).

Having a circuit with one of the output types I mentioned above would allow more people to undertake projects such as this without being locked in to a particular brand of PLC or having to spend tons of money. Also, I think we alll need to be aware of the limitations of any hardware/software solutions we put together...to do otherwise just doesn't same rational.

[gabe21804]

Blitz: This is for you, I didn't forget about you. If you need any more info, let me know

http://home.comcast.net/~rgabriel55/224wiringmodules.JPG

M is your negative for your dc power
L is your postive of your dc power
The green lines are your grounds, the symbol there linked too means ground.

JavaJaws: I understand your priorities, I wish there was a cheaper product that was commerical I found a company that made interfaces for plc's specifically but they never returned a phone call nor did they email me back. I'll try and find the site again, you may have better luck, the prices are not posted though.

Edit: Heres the site java, there isn't too much data on them.
http://www.bat4ph.com/bat/b20.htm

[inerratum]

Thanks gabe, that will be helpful. Now i can finish up a diagram of what i need. Lookin at the analog input module it looks the the inputs will have 3 leads. What are the 3 and how do they connect to the plc(which to RA,a+,a-)?

[slug]

They emailed me a quote for the b20, $360. About $300 overpriced.

[Sanjay]

I thought this was interesting.. since they claim it iterfaces directly to a PLC. Have no idea what it costs.

sanjay.

Differential pH probe with Built-In 4-20 mA Two-Wire Transmitter Wires direct to PLC

The AquaMetrix P65 differential pH probe with built-in two-wire 4-20 mA transmitter eliminates the need for standard pH transmitters by wiring directly to a PLC over twisted pair cabling. The 4-20 mA signal generated by the P65 is much less susceptible to electromagnetic "noise", and travels farther than standard pH mV signals.

Offering true three-electrode differential pH measurement, which reduces ground loop interference and has been used internationally in thousands of applications, the AquaMetrix P65 probe is available in 1-1/2" threaded body and 1-1/4" variable insertion depth models. Both models come with easily replaceable double junction salt bridge for extended service life. For more information contact Customer Service at 1-800-742-1413, or sales@aquametrix.com. AquaMetrix Inc. has been manufacturing rugged and reliable instrumentation for over 45 years.

[javajaws]

Originally posted by slug
They emailed me a quote for the b20, $360. About $300 overpriced.

I also got a quote for the same thing. However, they also included a doc on programming a PLC to perform calibration, etc...including RLL examples for DirectSoft. If anyone wants a copy send me a PM with your email address.

[inerratum]

I got a quote for a hanna PH transmiter (HI 8614) that was $348.00 so the b20 certainly isnt cheaper than other transmitters that are available.

[javajaws]

Originally posted by BlitzM4
I got a quote for a hanna PH transmiter (HI 8614) that was $348.00 so the b20 certainly isnt cheaper than other transmitters that are available.

I think you can get that one for $250 at automatedaquariums.com. Still overpriced though...

[easttn]

Here is a link to a datalogger (and related peripherals), might be of some use for you guys.

Logger (http://www.onsetcomp.com/)

I have not used any of their products.

[inerratum]

I looked at the instructions for the hanna ph transmitter. The only connections it has are 2 for a temp probe/resistor for temp compensation and 2 more for the 4-20mA loop (+VE Loop and -VE Loop) would this just connect to the plcs A+ and A- or is there more to it than that?

[gabe21804]

Originally posted by BlitzM4
I looked at the instructions for the hanna ph transmitter. The only connections it has are 2 for a temp probe/resistor for temp compensation and 2 more for the 4-20mA loop (+VE Loop and -VE Loop) would this just connect to the plcs A+ and A- or is there more to it than that?

The third connection is for a shield on the circuit, its a must have. You'd run shieled wire to the transmitter and ground it only on one side which is the third connection on the module.

[javajaws]

Originally posted by BlitzM4
I looked at the instructions for the hanna ph transmitter. The only connections it has are 2 for a temp probe/resistor for temp compensation and 2 more for the 4-20mA loop (+VE Loop and -VE Loop) would this just connect to the plcs A+ and A- or is there more to it than that?

You've got to provide it some power (12-30 vdc) somehow. What instructions are you looking at?

[inerratum]

http://www.hannainst.com/downloads/instr/hi8614.pdf

here you go, the instructions show no 3rd connection and no power connection.... but it does say it needs 18-30VDC so it must connect somewhere.

The 4-20mA loop cant provide power to the transmitter?

[gabe21804]

The third connection isn't going to be showed, a shield on a wiring is nothing more than merely a grounded connection on a foil/wire guard on one side of the wire, if you ground both sides you'll create an inductor and put tons of noise into the circuit. Not sure on what the hanna transmitter does, the circuit I have provides power to the transmitter, but the ph reading is measured in mV's not mA's, which is merely solved by turning the input module to a 0-5v setting. Issues that arise with the 4--20mA are going to be your not going to be able to run an ORP probe or conductivity probe on the same circuit, most of these probes are measured at the mV level, I know for sure ORP is because the standard reading on any ORP meter is mV's.

If you don't use a shielded wire on the feed into the analog input module, your readings most likely will be skewed, considering our tanks are havens for EMF(MH's,VHO's, pumps..etc), I'd suggest a 18G twisted, shieled wire, stranded or solid. And keep it a min. of 1/4 of an inch from other wiring.

I'm waiting on a resistor/capicitor/pto order from digikey, its supposed to be here friday. Along with the probe order from Marine Depot that will be here Monday. By monday I should have a prototype of my circuit, I've also order calibration solution at the following levels 4,7,10. This should give us an idea on the accuracy of this circuit. Depending on how this goes, and how the circuit functions I may make a few for people who are interested in a cheap alternative to a commerical transmitter.

[inerratum]

I am waiting to see the results of the circuits you have. But if all else fails I can spend $600 on transmitters and still be under what I would have spent for an AC2 and still have complete flexability that the AC2 doesnt have. Hanna makes 4-20ma transmitters for PH/ORP/and conductivity so I dont have a problem going the 4-20mA route if needed.

[javajaws]

Originally posted by BlitzM4
http://www.hannainst.com/downloads/instr/hi8614.pdf

here you go, the instructions show no 3rd connection and no power connection.... but it does say it needs 18-30VDC so it must connect somewhere.

The 4-20mA loop cant provide power to the transmitter?

OK, according to the documentation for the DL06 4-20 mA analog input (via wiring diagram in their documentation):

For 2-wire transmitters:

Connect the +VE of the transmitter to the +vdc of the power supply. Connect the -VE of the transmitter to the + 4-20mA analog input. Connect the -vdc of the power supply to the - 4-20mA analog input.

[javajaws]

What's the easiest way to keep track of the total time a contact has been closed (i.e. to keep track of how long a pump/light was on, etc.). The count will be in many hours...

Most timers don't seem to like to keep time for that long...so I assume I'll have to check timestamps and calculate on-time for each on/off cycle? Other approaches?

[inerratum]

Thanks javajaws after looking in the instructions thats what it seems to show.

[gabe21804]

Originally posted by javajaws
What's the easiest way to keep track of the total time a contact has been closed (i.e. to keep track of how long a pump/light was on, etc.). The count will be in many hours...

Most timers don't seem to like to keep time for that long...so I assume I'll have to check timestamps and calculate on-time for each on/off cycle? Other approaches?

You could use a counter, and count the cycles the output has been closed. From there you can divide it by the cycle time and get a accurate repersentation of time. I tried it on the s7, it worked down to the tee.

Or you could have a timer trigger a counter when it hits a certain time frame, for example when 15 mins have passed it adds a count to the counter. To get the time you would create a math expression to multiply the counter by 15, and add whats ever on the time to it. This method is less memory intense, and doesn't force the plc to count every 20ms, as it would have to if the counter was counting a cycle.

Both of these would work, I'd opt for the second one to save cpu resources.

[easttn]

Roy,

If you need any R's C's, Xistors, relays or DIPs send me a PM. Got twenty years of the stuff.

Java,
These PLCs have a real time clock and load TOD (time of day) on every pass of reading the stack, it measured in mSand accurate to less than 2min/ month. Events like lighting and such are enabled and disabled as the day passes, no timers for these perse. If you do need timers for delays and what not, there are 64 - 1ms, 16 - 10ms, and 236 - 100ms ones available. Roy understands this I believe, but I don't..yet. There is a battery backup that is good for 190 hours. (Doh, Roy beat me to it.)

[gabe21804]

Doh, wish I'd known before I placed a digikey order. Im having trouble finding gold plated female bnc ends that are made for a pcb board.

Originally posted by easttn
Roy,

If you need any R's C's, Xistors, relays or DIPs send me a PM. Got twenty years of the stuff.

Java,
These PLCs have a real time clock and load TOD (time of day) on every pass of reading the stack, it measured in mSand accurate to less than 2min/ month. Events like lighting and such are enabled and disabled as the day passes, no timers for these perse. If you do need timers for delays and what not, there are 64 - 1ms, 16 - 10ms, and 236 - 100ms ones available. Roy understands this I believe, but I don't..yet. There is a battery backup that is good for 190 hours. (Doh, Roy beat me to it.)

[javajaws]

Originally posted by gabe21804
Or you could have a timer trigger a counter when it hits a certain time frame, for example when 15 mins have passed it adds a count to the counter. To get the time you would create a math expression to multiply the counter by 15, and add whats ever on the time to it. This method is less memory intense, and doesn't force the plc to count every 20ms, as it would have to if the counter was counting a cycle.


I think this was the approach I was going to take until I re-read the timer instruction docs...on the DL06 an accumulating timer can accumulate 9999999.9 seconds (2777 hours). I'm working on some logic to keep track of my RO/DI unit usage and I think this will be enough before I hit a reset button (and replace the filters, etc.). If I decide I need more time before reset I can just add some extra logic to do like you suggested and increment another memory location every X minutes/hours/etc. (I'll have to do that to keep track of bulb hours I'm sure...).

[javajaws]

Well, I'm pretty happy right now. My DL06 came in yesterday and I've got the first part of my reef program up and running...logic to maintain my freshwater reservoir. Here's what I've got:

3 float switches: 1 low, 1 high, 1 high alarm (I should probably add a low alarm float as well...)

The logic in the PLC turns on the RO solenoid when the low float closes. It continues to fill until the high or alarm float opens.

If the alarm float ever opens, an alarm bit is set (currently displayed on the PLC display). This is so that I know my high float is stuck and needs attention. This can be reset be flipping a bit (eventually with a button somewhere).

Each time a fill cycle starts I increment a counter (just for fun, but it might help me calculate evap rates).

I also keep track of how long it took to fill (so I can track RO/filter efficiency). I store these stats in a table which I'll eventually use to plot a trend chart somewhere. When I know the approximate max time it takes to fill I'll add some alarm code in there to prevent the RO from being on too long in case both high floats fail.

I also sum all of those fill times in to a separate memory location to keep track of the total time the RO has been run. I'll eventually display this value too.

All of the RO stats can be reset by flipping a bit (for when you change the filters/membrane).

I've already thought of lots of other cool things to do with this...delayed on/off for fast flush of the membrane before each cycle, measuring TDS of the RO and DI outputs, etc.

If anybody wants the program I'll be happy to share...but remember its for an AD DL06.

[Sanjay]

I am interested in the hardware specifics that you are using to do this, other than the PLC - eg, which float switch, etc.

sanjay.

[javajaws]

Originally posted by Sanjay
I am interested in the hardware specifics that you are using to do this, other than the PLC - eg, which float switch, etc.

sanjay.

Its just 3 float switches from floatswitches.net. I have them mounting upside down with a pile of PVC pipe fittings so that they are positioned one above the other. Similar to the second picture on this link: http://www.reeftek.com/reef-relief/index-images.htm.

Everything is still in "test" mode...so I don't yet have the float switch "array" mounted in a container yet...it's just strapped vertically next to my computer and PLC for testing.

[gabe21804]

Update, Ph Transmitter:

I got my order from digikey today, I breadboarded the prototype circuit. Monday my order from marine depot will be in and ill have a ph probe to test it with.

[Sanjay]

javajaws:

your link is not working.

sanjay.

[Sanjay]

Roy:

Do you have pics of your wiring and setup ?

sanjay.

[gabe21804]

Originally posted by Sanjay
Roy:

Do you have pics of your wiring and setup ?

sanjay.

As far as my whole setup? Or this ph circuit?

I'll post some pictures of both tommroww, as far as wiring are you looking for wiring diagrams of the setup, or pictures of of the wiring within the enclosure?

[slug]

If it is the circtuit using the lmc6001 there is some info on the ph circuit on the data sheet: http://www.national.com/ds/LM/LMC6001.pdf

[Sanjay]

Originally posted by gabe21804
As far as my whole setup? Or this ph circuit?

I'll post some pictures of both tommroww, as far as wiring are you looking for wiring diagrams of the setup, or pictures of of the wiring within the enclosure?

Roy:

I am looking right now for pictures of the wiring inside the enclosures. trying to get a feel for how to lay this all out. there has to be a nice way, right now I have a tangle of wires.:D

I am going to try mounting all this on din rails, but I cant find the rails anywhere locally... all I get is blank stares. Online sites want me to buy 20 rails at a time.

Also what kind of wires are best suited for this internal wiring of the relays, switches etc. Right now I just grabbed what ever was laying around the house.

As you can tell, my electrical DIY skills are quite lacking.:)

sanjay.

[gabe21804]

Originally posted by slug
If it is the circuit using the lmc6001 there is some info on the ph circuit on the data sheet: http://www.national.com/ds/LM/LMC6001.pdf

I posted that schematic a page back ;) , but that is the one I'm using. That datasheet explains it all, just make sure you use a regulated 5vdc ps for it, and a regulated 12vdc power supply. If there cheap wall transformers make sure your meter them. Most of those supplies will flux back and forth by .5 to .25 volts....that can be solved by using a capacitor to smooth out the voltage.

But like easttn said, make sure you solder the female bnc end to the pin on the opamp, don't use a wire or pathway to connect it. Also make sure you use a platinum or gold bnc female bnc end.

[gabe21804]

Originally posted by Sanjay
Roy:

I am looking right now for pictures of the wiring inside the enclosures. trying to get a feel for how to lay this all out. there has to be a nice way, right now I have a tangle of wires.:D

I am going to try mounting all this on din rails, but I cant find the rails anywhere locally... all I get is blank stares. Online sites want me to buy 20 rails at a time.

Also what kind of wires are best suited for this internal wiring of the relays, switches etc. Right now I just grabbed what ever was laying around the house.

As you can tell, my electrical DIY skills are quite lacking.:)

sanjay.

I'll post some pictures later today, try digikey.com. You can buy rails in qty's of 5 I think. There catalog is a 1600 page pdf file you'll have to go through. You also get a good deal on din terminal blocks..etc Only bad thing is they have a $5 handling fee if the order is under $25.

[javajaws]

Originally posted by Sanjay
javajaws:

your link is not working.

sanjay.
Remove the dot at the end... http://www.reeftek.com/reef-relief/index-images.htm

[slug]

I saw you already posted that schematic but thought the data sheet might be usefull too.

When I got samples of the chips one of them was one of the tiny surface mount types because I didn't specify a package, so if anyone else requests samples make sure and get the right part. I think I'm going to try and solder leads on it but I have to high a wattage and not a fine enough tip soldering iron =(

[slug]

I wired up just the left half of the circuit using only the lmc6001 and a couple resistors and this seems to work. I get 295 mV in ph 4 solution and 29 mV in ph 7 solution. A ph 10 solution should give me negative mV but I can't find one.

I think this is good enough to read into a data acquistion device. It makes the circuit super simple and the inversion and zeroing can be done in software.

[gabe21804]

Originally posted by slug
I saw you already posted that schematic but thought the data sheet might be usefull too.

When I got samples of the chips one of them was one of the tiny surface mount types because I didn't specify a package, so if anyone else requests samples make sure and get the right part. I think I'm going to try and solder leads on it but I have to high a wattage and not a fine enough tip soldering iron =(

Make sure you get dip's when you order the samples, the datasheet did help a ton, so the second chip isn't necessary? Ive got the circuit done just waiting on the probe.

[barebottoms]

http://www.vernier.com/probes/probes.html?ea-bta&template=standard.html

[sailfinreef]

I just stumbled in on this thread and it seems very interesting. I have been using allen bradleys plc 3 with a hand controller that i got for free to controll lighting and temp for a while. I really dont have much use for the ph monitor, but if you guys want me to look over some code or have a question I might be able to answer it. I am familiar with quite a few logic Swords.

[gabe21804]

Originally posted by sailfinreef
I just stumbled in on this thread and it seems very interesting. I have been using allen bradleys plc 3 with a hand controller that i got for free to controll lighting and temp for a while. I really dont have much use for the ph monitor, but if you guys want me to look over some code or have a question I might be able to answer it. I am familiar with quite a few logic Swords.

Sounds great, I'd like to compare how your doing temp control, to how I am. Althougth were using different plcs the logic should look similar.

[eleben]

Originally posted by barebottoms
http://www.vernier.com/probes/probes.html?ea-bta&template=standard.html

Did anyone take a look at the link? This is straight from the datasheet:

"Use our Electrode Amplifier to collect data with almost any electrode that has a BNC connector. This includes electrodes from Vernier such as our pH electrode (order code 7120B), or third-party electrodes, such as pH, ISE (ion-selective electrode), or ORP (oxidation-reduction potential). The Electrode Amplifier can produce an output in mV, pH (when using a pH electrode), or you can perform your own 2-point, linear calibration."

Just wondering if we can use this for any of our applications since it can accept "an electrode with a standard BNC connector. It amplifies a .390 mV to +400 mV range to the 0-5 V range..."

It would be awesome if it works considering it is only $40

Thanks,
David

[slug]

It looks like it would work great. It's nice that it amplifies it to a range closer to what most analog in devices read. I'm going to stick with the single lmc6001 because I'd need 3 and I'm cheap ;) and it seems to work pretty well with the equipment I have.
Whether or not you can get an accurate ph from the mv output from one lmc6001 depends on the range and resolution of your analog in.

[gabe21804]

Originally posted by slug
It looks like it would work great. It's nice that it amplifies it to a range closer to what most analog in devices read. I'm going to stick with the single lmc6001 because I'd need 3 and I'm cheap ;) and it seems to work pretty well with the equipment I have.
Whether or not you can get an accurate ph from the mv output from one lmc6001 depends on the range and resolution of your analog in.

Same here I need two ph transmitters, and I'm also cheap. Are you getting the lmc6001 and 6041 as samples from national? I figured it costs about $8 in parts to make these circuits, depending on how my tests go when I get a probe I'll be getting some single layer pcb boards made, maybe a run of 15 or so which would end up being about $3 a board, the circuit would be roughly 3"x3", I dont want to crame it any tighter becaues it has to be hand assembled. It'd be nice if someone could make an arylic case, I tried my handy work with arylic and it didnt turn out too well.

So your looking at roughly $11 in parts with no case for a functional ph transmitter. I'm still in need of platnimum or gold female bnc ends that are made for a pcb board. I only have two gold ones left and I'm having trouble finding that in qty's smaller than 50 cheap.

<b>Slug:</B> What type of plc are you using? I don't remember you talking about it at all?

[barebottoms]

http://www.alliedelec.com/cart/ProductDetail.asp?SKU=713-9041&SEARCH=gold+bnc&ID=&DESC=31%2D5329%2D52RFX
http://www.newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/searchPage2.jsp?x=0&Ntt=gold+bnc&Nty=1&N=4&y=0&Ntk=gensearch
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=301932&e_categoryid=583&e_pcodeid=52312

[gabe21804]

Originally posted by barebottoms
http://www.alliedelec.com/cart/ProductDetail.asp?SKU=713-9041&SEARCH=gold+bnc&ID=&DESC=31%2D5329%2D52RFX
http://www.newark.com/NewarkWebCommerce/newark/en_US/endecaSearch/searchPage2.jsp?x=0&Ntt=gold+bnc&Nty=1&N=4&y=0&Ntk=gensearch
http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=301932&e_categoryid=583&e_pcodeid=52312

Thanks barebottoms, this helps out alot, the bnc ends up being the most expensive part of this board lol.

[slug]

I'm not using a plc, I'm using http://beckhoff.com/english/busterm/bk9000.htm

It's what I mostly program for at work so is easiest and available for me.

[sailfinreef]

Originally posted by slug
I'm not using a plc, I'm using http://beckhoff.com/english/busterm/bk9000.htm

It's what I mostly program for at work so is easiest and available for me.

that looks like it might be alittle over my head, plc's are a lot simpler. I would imagine that there are very few limits to that baby once you get the languages down.

[javajaws]

What sort of logic are you guys incorporating into your program for turning on/off your MH (and other) lights? I don't plan on doing anything fancy with moon phases etc..but what I plan on is:

- Master on/off override
- Delayed on (5 min) for power off/on cycles (to let the MHs cool down before refiring).
- Adjustable memory settings for on/off times for each MH.
- Hour meter (with reset) for maintenance. Optional maintenance light when hour meter reaches a preset number.

Anything else I should think of? Anybody add a light sensor in their canopy to detect cases where the bulb fails to fire correctly?

[slug]

Gabe21804,

Why do you need to use gold or platinum connectors? I can't see that they are really necessary.

[sailfinreef]

java jaws,a sequencer would probably be easiest for turningn the lights on and off. as far as keeping a record of how long they were on I think that would be pretty easy especially if the plc Sword would allow you to easily change the time constants.

[javajaws]

Originally posted by sailfinreef
java jaws,a sequencer would probably be easiest for turningn the lights on and off. as far as keeping a record of how long they were on I think that would be pretty easy especially if the plc Sword would allow you to easily change the time constants.

I don't have any problems getting any of this programmed (I'm a programmer by trade...PLC logic is a walk in the park so far)...I'm just looking for cool features I might not have thought of that I could incorporate into my setup.

[gabe21804]

Originally posted by slug
Gabe21804,

Why do you need to use gold or platinum connectors? I can't see that they are really necessary.

They are a better conductor, the better conductor you have on that bnc end the better your readings will be. I want to rule out any all accuracy issues I can. I've read a few sites that talk about building these circuits and they've all recommended using atleast gold plated connectors.

When I work on cctv systems and were using extremely high resolution cameras we use gold plated bnc connectors to, to do the same thing give the best possible connection you can have.

[gabe21804]

Originally posted by javajaws
What sort of logic are you guys incorporating into your program for turning on/off your MH (and other) lights? I don't plan on doing anything fancy with moon phases etc..but what I plan on is:

- Master on/off override
- Delayed on (5 min) for power off/on cycles (to let the MHs cool down before refiring).
- Adjustable memory settings for on/off times for each MH.
- Hour meter (with reset) for maintenance. Optional maintenance light when hour meter reaches a preset number.

Anything else I should think of? Anybody add a light sensor in their canopy to detect cases where the bulb fails to fire correctly?

Thought about the light sensor, decided that for now its not important maybe in the future, I just wanted to get the system up and running.

Why do you need a 5 min on/off delay for the halide? If your using a realtime clock and checking its time with a compare statement its going to turn on and off at the specified time. Giving it more than enough time to cool down..etc Maybe I'm missing something.

On another note the marine depot order came on time, the probe is here. I'll see if I can't get some results for you guys tonight.

[javajaws]

Originally posted by gabe21804
Why do you need a 5 min on/off delay for the halide? If your using a realtime clock and checking its time with a compare statement its going to turn on and off at the specified time. Giving it more than enough time to cool down..etc Maybe I'm missing something.

Lets say its the middle of the afternoon, MH lights are on. You then loose power for a few seconds/minutes (storm, etc.). I've heard if you don't let MHs cool down before refiring they may not successfully restart. Adding the delay during power on of the PLC is a safeguard against this.

This is equivalent in functionality to Digital Aquatic's "sure-on" feature in their ReefKeeper controller.

- Jason

[gabe21804]

Originally posted by javajaws
Lets say its the middle of the afternoon, MH lights are on. You then loose power for a few seconds/minutes (storm, etc.). I've heard if you don't let MHs cool down before refiring they may not successfully restart. Adding the delay during power on of the PLC is a safeguard against this.

This is equivalent in functionality to Digital Aquatic's "sure-on" feature in their ReefKeeper controller.

- Jason

I knew I was missing something, sounds like a good idea. I might just have to do that, something you may want to think about is a transfer switch system like mine.

I use 120AH 12VDC Sealed Lead Acid batteries, when the power goes out a 4dpt relay switches the load from ac current to battery / inverter current. Then an input on the plc closes and starts shutting stuff off thats no essential to a power outage, all lights in my case (thats my only high current device I need to lose). From there it keeps running in "power save mode" til power is restored (I have enough batteries to keep me running for roughly 11.5 - 12 hours.

Your idea now reallymakes me think I still need to do this, because if I lose power and this system kicks in, I'll still need a timer in place to make sure if it comes back quickly the MH will not turn on for 5 mins or so. It would also come in handy with the backup system itself, meaning when the system comes on it has to stay on backup for atleast 15 mins. This way the system isn't switching back and forth if there are a few quick outages seconds to mins apart (Ive had this happen before).

Wow Java, you made me think of some really bad things that could be happening without these timers in place especially with my backup system.

[gabe21804]

Originally posted by gabe21804
I knew I was missing something, sounds like a good idea. I might just have to do that, something you may want to think about is a transfer switch system like mine. I'd only use a system like this if you don't live in a house. If I lived in a house I'd invest in a backup propane generator that has an automatic transfer switch, with enough juice to power half of a 200A service.

I use 120AH 12VDC Sealed Lead Acid batteries, when the power goes out a 4dpt relay switches the load from ac current to battery / inverter current. Then an input on the plc closes and starts shutting stuff off thats no essential to a power outage, all lights in my case (thats my only high current device I need to lose). From there it keeps running in "power save mode" til power is restored (I have enough batteries to keep me running for roughly 11.5 - 12 hours.

Your idea now reallymakes me think I still need to do this, because if I lose power and this system kicks in, I'll still need a timer in place to make sure if it comes back quickly the MH will not turn on for 5 mins or so. It would also come in handy with the backup system itself, meaning when the system comes on it has to stay on backup for atleast 15 mins. This way the system isn't switching back and forth if there are a few quick outages seconds to mins apart (Ive had this happen before).

Wow Java, you made me think of some really bad things that could be happening without these timers in place especially with my backup system.

[javajaws]

Originally posted by gabe21804
Wow Java, you made me think of some really bad things that could be happening without these timers in place especially with my backup system.

Glad I could "help". You've given me some good stuff too!

- Jason

[Sanjay]

Originally posted by javajaws
Lets say its the middle of the afternoon, MH lights are on. You then loose power for a few seconds/minutes (storm, etc.). I've heard if you don't let MHs cool down before refiring they may not successfully restart. Adding the delay during power on of the PLC is a safeguard against this.

This is equivalent in functionality to Digital Aquatic's "sure-on" feature in their ReefKeeper controller.

- Jason

I have never had any problems with MHs not starting if you do not let them cool down. They automatically have a restrike period where they will not start if not sufficiently cool.

sanjay.

[Sanjay]

How do you snap open the DIN rail clips on the Siemens s7. ? Did not want to break the clip.

I found some DIN rail and wanted to mount it on it.

sanjay.

[Sanjay]

Originally posted by Sanjay
How do you snap open the DIN rail clips on the Siemens s7. ? Did not want to break the clip.

I found some DIN rail and wanted to mount it on it.

sanjay.

Igonre this, I figured it out.

sanjay.

[javajaws]

Originally posted by javajaws
What sort of logic are you guys incorporating into your program for turning on/off your MH (and other) lights? I don't plan on doing anything fancy with moon phases etc..but what I plan on is:

- Master on/off override
- Delayed on (5 min) for power off/on cycles (to let the MHs cool down before refiring).
- Adjustable memory settings for on/off times for each MH.
- Hour meter (with reset) for maintenance. Optional maintenance light when hour meter reaches a preset number.

Anything else I should think of? Anybody add a light sensor in their canopy to detect cases where the bulb fails to fire correctly?

OK, I thought of 1 more "must have" feature (at least for me): a kill switch for the current lighting cycle (as opposed to the master MH kill switch). I like to have my lights on a little later in the evening so I can enjoy the tank when I'm home at night. But the tank is in my living room and sometimes I want to kill the lights just a little early when its movie time (DLP projector...doesn't like any ambient light at all). So a "kill this light cycle" switch would kill the lights for the rest of the light cycle...the switch would reset itself before the next light cycle (haven't thought about how yet) and I won't have to remember to flip a switch or push a button the next morning to turn them back on. Sweet.

[swissfish]

as far as I know I would only need about 8 digital outputs and about 4 analog inputs.
I you guys get the Siemens compact PLC for about $150 you'll be ready to rock in no time since the digital in/out puts are rated for 10A each.
And as far as I know there are PID loops available.

[gabe21804]

Originally posted by javajaws
OK, I thought of 1 more "must have" feature (at least for me): a kill switch for the current lighting cycle (as opposed to the master MH kill switch). I like to have my lights on a little later in the evening so I can enjoy the tank when I'm home at night. But the tank is in my living room and sometimes I want to kill the lights just a little early when its movie time (DLP projector...doesn't like any ambient light at all). So a "kill this light cycle" switch would kill the lights for the rest of the light cycle...the switch would reset itself before the next light cycle (haven't thought about how yet) and I won't have to remember to flip a switch or push a button the next morning to turn them back on. Sweet.

JavaJaws: Just create a latching feature that when input such and such is activated it latches on until a certain set of circumstances are met. In your case have it until the realtime clock makes it to its designated "off" time. At that point the latches ends and allows the cycle to go back to normal and the lights will turn on in the morning. Hope this helps.

I'd also ad a master reset button, or a reset button for just the lights. Incase you want to restart the lights before the latch ends.

[gabe21804]

Originally posted by swissfish
as far as I know I would only need about 8 digital outputs and about 4 analog inputs.
I you guys get the Siemens compact PLC for about $150 you'll be ready to rock in no time since the digital in/out puts are rated for 10A each.
And as far as I know there are PID loops available.

What version is this, and whats the cpu revesion? Also does it have the estand 1.0 bus on it to connect to other modules? What we really need is s7 programming cables, there are a few guys on here with s7's already but have not been able to find ppi programming cables.

[H20ENG]

I think the problems with lamp restrike after power outages are mainly with electronic ballasts. When they first start up, it pulses the lamp with high voltage to fire it up, then runs a constant voltage through it while running.
If the lamp has been running, that pulse will not restrike the arc. it will continue to feed normal "run" voltage to the lamp when in fact the lamp never started.
That was my take on it anyway.
Chris continues lurking and learning....

[javajaws]

Originally posted by H20ENG
I think the problems with lamp restrike after power outages are mainly with electronic ballasts. When they first start up, it pulses the lamp with high voltage to fire it up, then runs a constant voltage through it while running.
If the lamp has been running, that pulse will not restrike the arc. it will continue to feed normal "run" voltage to the lamp when in fact the lamp never started.
That was my take on it anyway.
Chris continues lurking and learning....

...and I've got electronic ballasts. Better safe than sorry...that's what they always say. Its not like it costs anything to implement the delay...except for a few bytes of memory that is. :)

On a side note, I notice my electronic ballasts generate minor electrical noise in my house (like static on TV, etc.)...will this cause the PLC any problems (I would think not...but better safe than...well, you know...)?

[gabe21804]

Originally posted by javajaws
...and I've got electronic ballasts. Better safe than sorry...that's what they always say. Its not like it costs anything to implement the delay...except for a few bytes of memory that is. :)

On a side note, I notice my electronic ballasts generate minor electrical noise in my house (like static on TV, etc.)...will this cause the PLC any problems (I would think not...but better safe than...well, you know...)?

Don't put them in the same enclosure or near each other. I have mine in the canopy, and my plc near the stand. As long as there is some distance between the two you'll be fine.

[easttn]

The sale forum does not last an hour, If your into this thread please follow here (http://www.reefcentral.com/forums/showthread.php?s=&threadid=557479)
PM for any details.

[Stbringer]

Wow! Plc's at last!!
Will be HAPPY to offer any help on logic design for reefs, data collection, suggestions, etc.
One caution, most plc contacts are rated like 10a for a relay output. There is a catch though, and that is most contacts share a common.
This is not always the case, but often the sum of the contact amperage is greater than the amperage per common. In simple terms, the make/break characteristics of the relay contacts are collectively higher than the ampacity of the board traces that provide power to the line side of the contact. Again, not always the case, but in MANY cases.

I have seen a great many good ideas and implementations here, and am a bit behind. I was thinking of trying a tc/mv card or an RTD card for PH but never got around to checking the electrical characteristics of the probe.

It seems the S word is taboo here, but I am very experienced with accumulated data, data logging, and conversion to excel, etc. to plot reef params.

Again, just an offer for assistance, and I can definitely learn a thing or two here. PM me if I can help!

[Stbringer]

OH, don't know if this has been handled or not, BUT for those of you using backup power, always keep a digital input available for your normal power ok, and one for "backup power on". This will allow you to determine alternative logic for low power, etc. It may even be of use for the plc to switch back to standard power after a preset time saving the battery but sailing through repeated brownouts, etc.

For items like DIN rail, oiltight/watertight buttons and switches, check your local yellow pages for electrical distributors that carry Siemens/A-B/ etc. plc's. They will have it and more.

[inerratum]

Bump, dont want this project to die.

I have the programming cable on the way, thanks easttn, so I can finally start to get mine setup. Still need the thermocouple module and the analog in module but at least I can start getting the basic timers setup soon.

Does anyone have a link to thermocouples that are saltwater safe and will work well for this application?

[Stbringer]

I recommend a Type J thermocouple for the temperature range in this application. They are made of a juncture of Iron/Constantan and in the US color coded Red/Wht. In most applications that need isolation of the probe, a threaded thermowell made of Inconel is used. Others have small already encapsulated probes. Try www.omega.com .
Oh, for accurate readings, you will need thermocouple wire also. Copper wire introduces error and temperature resistivity differences.
I have only purchased for industrial applications before, guess I shoud get looking!

[jgwinner]

Wow, great thread! I bought some uC's a long time ago to build something myself but never finished the project.

These PLC's are programmed in 'ladder logic' or C code?

'soft start' would be nice too, is there a way to syncronize the digital out with a zero crossing?

== John ==

[javajaws]

They are coded with RLL (ladder logic). I'm not familiar with a "zero crossing"...what's that refer to (I'm assuming some phase condition on the AC line)?

[Stbringer]

Naw, most of the outputs are Triac anyway, and only switch on the 0 cross. The relays response, etc. and the time from output set high in data table to output table update to backplane pretty much rule out digitally programmed soft start... Unless you want to bang it a few times on the way to speed.

Most do ladder logic, statement logic, and Siemens has Pascal available. Some small off brands and other controllers may do the C.

[jgwinner]

Zero crossing means a timer signal from an optocoupler based on an AC in (usually the power supply). In other words, it would be a trigger whenever the incoming a/c hits 0. What you would do is latch a signal saying 'turn on' to the pumps, and then when the zero crossing triggers, actually turn on the outputs.

Some solid state relays do this automatically, which is handy. those are probably 5-10 bucks a piece, can't remember current prices. It's been a while since I looked at this stuff.

One thing I've always wondered is if you could run an aquarium pump on 'half speed' by only passing through say every other waveform (DC if you will) or doing 2 on 2 off kind of a thing. The zero crossing detector would allow messing around with that too.

Edit: Triacs don't wait for 0 crossing, they just don't turn OFF until you have a zero crossing. Triac's are two back to back SCR's which is a diode with an 'input' - once you pass in a signal to the input the diode turns on, permanently until you remove power. Handy little things, no heat disipation at all.

Dimmers use triac's that trigger 'on' somewhere halfway up the sine wave. They then turn off at the zero crossing. I've made dimmers for DJ's based on this.

== John ==

[Stbringer]

Oh, javajaws, yea, you hit it.. the ac as it crosses 0 on the up or on the down is the 0 Cross. Most solid state DC outputs are not limited by this, but the actual Hz you can get out of a plc is sort of flaky in most cases, as it relys on scan time, etc. Most of the industrial motor starters/vfd's that would be used with a PLC contain the soft start so they generally don't build that into em.

[Stbringer]

jgwinner, you know your stuff!
(Guess we are typin at the same time, and you are faster!)
Best thing might be to use the hardware for the soft-start if you can rig it.

[Stbringer]

jg, what about firing a triac output to a 1/2 wave bridge set for the upper half, then later kicking on another 1/2 wave bridge set for the lower half??? Been a long time since I did the board level (20yrs) but know the speed limitations of most plc response pretty well, even if using PII interrupts. If you know of some kind of rig that would take a PWM output and convert each pulse peak and valley as a 1/2 cycle trigger, some of the smaller units do have a pwm out...

[javajaws]

How important is soft start and zero crossing? What benefits would that give us?

[DJ88©]

Less wear and tear on anything you need to start up.

A good analogy is dropping the clutch in a car when the engine is at 3,000 RPM all the time. Something will wear out in time.

Listen to a maxijet powerhead when you plug it in. YOu cna lessen the "chatter" with a soft start.

[jgwinner]

I'm surprised these PLC's have such speed limitations. I had been working with a 68hc11 single board computer a while ago and it had the 0 crossing built in. Geez, maybe I should dig that project out of retirement.

The PLC project seems nice and easy though, most everything is built.

The soft start is apparently disputed somwhat - my understanding is that no matter how you start the pumps they 'clatter' but it definitly would increase eletrical noise in any event.

Digital relays usually have a 0 crossing built in, including the 'hocky puck' relays.

Thanks for the kind words Stbringer, been a while since I did any professional EE work. Mostly doing C++, Oracle, IT stuff now.

[Stbringer]

HAHA! PLC's are fast for most industrial needs, and you deserve the praise. You remember what most of us forget, and clearly at that!

Ya, will get some noise, but maybe save the impeller some wear.

Problem with these little magnet motors is they need enough kick to light off initially or they just vibrate...
You are the man to ask, so say we fire the AC output to an SSR, it will then inherently light off the pump(s) at the 0 cross? The plc code can do the latching on/turning off on internal timers no problem.

Most of the 16pt and even some 8pt ac outs are very low resistive current rated outputs. The ssr would allow easy switching of multiples, larger pumps, etc. with virtually no penalty to the ampacity of the output card itself.

I use SSR's from time to time for resistive heating applications...PID algo. in the PLC. Using an SSR on an output for the heater(s) would allow you to kill them for sure in the event of a runaway temperature event (stuck thermostat in heater).

[jgwinner]

Here's a link to what I mean by hocky puck relay:

http://www.surplussales.com/Relays/RESSPlug-1.html

Although they didn't have much on stock today apparently. It'll give you an idea. The description for these don't say but I believe a lot of those have the 0 crossing built in.

[sailfinreef]

I just got back from pittsburg and I think I may be slightly confused about what you are talking about, i was under the impression when you ended your program it would stop the scan and restart it, if you dont end your program it will scan every chip on th plc then restart the scan. As far as a soft start up, I dont think it would be cost effective to get a frequency drive for a few pumps. the drive would not be worth the cost of replacing a pump every 5 five years. I have been using the old school allen bradelly plc 3 and using all the outputs to controll ice cube relays so I dont burn the board up.I thinki I may have not understood something I read though. if Im not making any sense could someone pm me and reexplain it to me.

[jgwinner]

>>As far as a soft start up, I dont think it would be cost effective to get a frequency drive for a few pumps. <<

Not sure what you mean by this - with a uC I would just activate the digital out for 'on' only at the exact instant the zero crossing bit activates. That's no more or less cost effective than anything else, it's just software if you have the zero crossing detector. What do you mean by a frequency drive?

== John ==

[Stbringer]

With a frequency drive, or a flux vector drive, they use like IGBT's to programmatically totally re-work the output to typically 3 phase motors for optimal slow starting, speed control, etc. In practice, even with a VFD rated 3 phase motor, and a fanstatic drive, you seldom want to run it below 20Hz to avoid heating the windings. Many of us PLC guys are dealing with motors ranging from 1-5000 hp, and 480-13,000V where even the rotor mass at rest can be a significant factor let alone if a load is attatched.

With a PowerFlex drive for example, you can program in a startup ramp rate in 1/10 seconds, etc. They are electrically noisy as heck though you could program an output sine of 120V 5 hz if you wanted to.

In the case of the tiny single phase motors we are dealing with, I am not sure how much impact starting on the 0 cross would have, as we will still be going from 0 to 60hz inside of one cycle....

That is why I was babbling about using two outputs and 2 1/2 wave bridges....which would effectively cut the rms output by 50% for starting (IF the little motor would START on 1/2 wave!) then kicking in the other half of the wave after a delay....Probably half baked, but looking for lower cost options...
Maybe one of the analog input ssr's used for heating applications..but still pricey!??

[Stbringer]

Anything cheap out there that would take an analog signal and use it to pass say 0-120v or 60-120v single phase? You could probably work something there for a much softer start and even give day/night profiles...

[jgwinner]

Right, but if there is an interrupt on the zero crossing then it's all just software.

All this takes is 3 things:

1) a 'zero crossing' signal on a digital input
2) a way to set an interrupt
3) a way to have an 'interrupte routine' so that you can turn on whatever you want only when you get the zero crossing signal.

For output, all you need is a radio shack Triac, maybe a buck. I would use one of the optoisolated ones.

I'll hook all this up as a test IF I can figure out number one and two above.

When I was originally doing this work, I was using a 68hc11 from Wheatstone Microsystems, Inc, that had the zero point crossing and the interupt routines (I was coding in assembler) but sadly they seem to be out of business now.

So is it possible with a PLC/ladder logic to have a routine that runs 'only' when an input goes 0 or 1, AND have it do this within say a few microseconds, potentially 60 times a second?

== John ==

[barebottoms]

Originally posted by jgwinner

When I was originally doing this work, I was using a 68hc11 from Wheatstone Microsystems, Inc, that had the zero point crossing and the interupt routines (I was coding in assembler) but sadly they seem to be out of business now.


Was that just 68hc11 based prototype board? Or was there any special software? Sounds like the freebie MIT Handy Board if it was just a uc based board:

http://handyboard.com/

[sailfinreef]

got ya, I was definatly looking at that wrong. its all coming clear now, haha.

[jgwinner]

It was an SBC, about 8" wide by 4 or something, not any specific form factor. The nice thing was that it routed all the A/D signals and the digital out's directly to headers so you could do whatever the chip was capable of.

The handy board looks nice - motor controls even, although in this case we really just need a digital out as I would always use some kind of opto isolated outputs.

The Wheatstone board had the optoisolators on every digital out pin but they weren't big switches, really just protection for the controller itself. I think there were 24 of them. With all the sensors I was planning I think I can exhaust 8 i/o's pretty fast.

I bought it at the time as I couldn't find any proto board 52 pin sockets for the blasted 68hc11's.

The only reason I went with the hc11 was that it had A/D built in, and I had some freeware C compilers; simple, not C++ but I could live with that for what we are doing. Due to the goofed up architecture of the 8051 series, a C compiler is real money, or was at the time. I did most of this work more than 6 years ago. Man I can't believe it's been that long.

So are interupt routines available for PLC / Ladder logic devices?

[Stbringer]

Some models do have STI or Selectable Timed Interrupt or IO based, PII Programmable Input Interrupt. PLC's are still WAY slower than the SBC. For rapid motion control apps, high speed operations, etc other devices are generally needed that the plc simply communicates with.

Nice sounding SBC!

[Stbringer]

Ok, some summary info on what has recently been discussed:
1. How about the PLC output going to one of the SSR's (rated 25A!) for control of MH fixtures!
2. Rolling data buffers needed for stabilizing analog readings and possibly providing better derived accuracy.
3. PLC output to SSR to control heaters a real possibility
Points we need to clarify...
Level control...1, 2, 3 or 4 point control.
I vote for 4 inputs, LowLow (shut of pumps to save them), Low to start fill, High to stop fill, High High to again stop fill if sensor fails..
But thats JMO...

[gabe21804]

Originally posted by Stbringer
Ok, some summary info on what has recently been discussed:
1. How about the PLC output going to one of the SSR's (rated 25A!) for control of MH fixtures!
2. Rolling data buffers needed for stabilizing analog readings and possibly providing better derived accuracy.
3. PLC output to SSR to control heaters a real possibility
Points we need to clarify...
Level control...1, 2, 3 or 4 point control.
I vote for 4 inputs, LowLow (shut of pumps to save them), Low to start fill, High to stop fill, High High to again stop fill if sensor fails..
But thats JMO...

I've got a few questions regarding your points.

1) I'm already using 12vdc icecube relays rated for 15amps on the contacts. Every 120VAC device is using one, I feel better knowing Im not running high voltage through the plc. How is this any different from an SSR? 15A is more than enough to handle the load of a a MH.

2) I didn't see where you addressed this above, could you go a little farther indepth on this.

3) Already using an icecube relay thats in a normally open state hooked to the plc, one on each heater. If the TC's pick up a high temp it energizes the icecube and turns off the heater. I did it this way so its failsafe, if the icecube dies its going to open the circuit. With two heaters the chances of two icecubes failing at the same time are about the odds of me winning the lotto.

4) Already with you on this one, I'm also using four inputs for my top off system. Along with two water sensors on the back glass of the main tank, and on the floor at the bottom of the back stand. If there trigger it puts the main return pump into a shutdown timeout squence, and the topoff system if its running.

Glad to have you on board, I'm sure your knowledge is goign to be extremely beneficial to this project, considering you do this for a living. I've managed to learn what I know in the last months, so bear with me most of the techie terms for plc's your using are taking awhile for me to catch on, I come from the world of fire alarms.

[Stbringer]

Howdy Gabe!

1) I'm already using 12vdc icecube relays rated for 15amps on the contacts. Every 120VAC device is using one, I feel better knowing Im not running high voltage through the plc. How is this any different from an SSR? 15A is more than enough to handle the load of a a MH.

-The ice cube relays are JUST FINE!! Unless you were using them for temp. control. The make/break action of time proportioned control for heating would kill an ice cube quickly. (Alternatives, Mercury relays, or SSR)

2) I didn't see where you addressed this above, could you go a little farther indepth on this.

-Ah, this was my error, and should have been in another thread, but does apply here. We should make a rolling buffer to filter out reading spikes on the analog. This technique is common for flow, temperature, etc...Picture 10 contiguous integers in a file. Each scan, you shift them all down one, drop the last, and move in a new analog reading at the top. Now, using floating point, add all 10, and then divide by 10. Then scale the "debounced" value. Not always necessary, some cards do it already, etc.

3) Already using an icecube relay thats in a normally open state hooked to the plc, one on each heater. If the TC's pick up a high temp it energizes the icecube and turns off the heater. I did it this way so its failsafe, if the icecube dies its going to open the circuit. With two heaters the chances of two icecubes failing at the same time are about the odds of me winning the lotto.

-No problem here, as you are not using time proportioned CONTROL, rather you are just using the contacts as an ENABLE. Time proportioned CONTROL would involve shifting the ice cube relay thousands of times a day.

4) Already with you on this one, I'm also using four inputs for my top off system. Along with two water sensors on the back glass of the main tank, and on the floor at the bottom of the back stand. If there trigger it puts the main return pump into a shutdown timeout squence, and the topoff system if its running.

-My hat is off to you!

Glad to have you on board, I'm sure your knowledge is goign to be extremely beneficial to this project, considering you do this for a living. I've managed to learn what I know in the last months, so bear with me most of the techie terms for plc's your using are taking awhile for me to catch on, I come from the world of fire alarms.

-Many thanks, glad to be aboard! Hope to do more good than damage.

-Good field, Silent Knight, Cerberus, Gamewell, Honeywell, Simplex... Most PLC'ers would have just a much trouble with your terms PIR, Duct Detector (finds ducks!?)

Thanks again and I will do my best!
John

[gabe21804]

I just wanted to give you guys an update.

My ph circuit should get tested this weekend, I've been held up by getting liverock for my tank, I finally got 43lbs of tonga ultra this weekend, although I got one peice too many and need to get rid of it.

After this weekend, I'll be back in the full swing of things with this project. I'm hoping these ph transmitter circuits are accurate, Im going to test them against a pinpoint monitor.

[ronc98]

I am just in the final stages of my controller Here is the link if you are interested.

http://www.reefcentral.com/forums/showthread.php?s=&threadid=556711

I have a little advice on your zero crossing cicuits. In my opinion I would not waste much time writting code to do this. You can get direct replacement Opto-Isolators that are Zero crossing. The 3041 is a direct replacement of the 3011. You should really be using an opto-Isolator anyway for protection in case you one of your Triacs fail. You do not want AC coming back to your controller or worse yet the user interface.

I connected finished my two PH probe circuits last night along with the software calibration. System has been running for a little over a week. ORP circuit is just a modified PH circuit. Rather simple.

If anyone needs any help shoot me a PM. I do this kind of stuff for a living.

Good luck Guys

R

[jgwinner]

R:

I agree about the zero crossing isolators, and already mentioned that in a post. I think you missed the point, however, we were speculating on throttling a powerhead by only passing 1/2 the AC into it by clipping out portions of the waveform at the zero crossing. Sort of a 'cheap frequency drive'.

[slug]

Would it be possible to pulse a seio down to 75% or so then back to 100% by mimicing a frequency drive in software?

[slug]

I guess that's a "no"

[slug]

Isn't it possible to control the speed of an ac motor (like a seio) by chopping off the peaks on the ac waves?

[Konadog]

slug, what your talking about is a variable frequency drive. There is a little more to it than just software. A VFD basically turns a sine wave to a square wave (chopping off the peaks), and by adjusting the frequency of them, you can speed or slow an AC motor. Well, that's the simple version of it anyway.

[slug]

Ok, thanks that makes sense. I guess there wouldn't be anyway to do what I was thinking turning a relay on and off.

[gabe21804]

Originally posted by Konadog
slug, what your talking about is a variable frequency drive. There is a little more to it than just software. A VFD basically turns a sine wave to a square wave (chopping off the peaks), and by adjusting the frequency of them, you can speed or slow an AC motor. Well, that's the simple version of it anyway.

Thats exactally what I was going to post, been out of the loop for the last week.

Rumor has it, that is what seio's controller is going to do when they release it. Hopefully they can do it cheaper than what an actual VFD would cost to do it. Its just not economical to run a VFD on a powerhead, by the time you add the vfd and the ph into the cost, you'll have a tunze + controller if not more spent.

[slug]

So something like a light dimmer is a bad idea on a seio? I somewaht understand what a light dimmer does, what does a vfd do to the ac signal?

[sailfinreef]

a vfd increases or decreases the frequency to an ac motor, most of them will change both frequency and voltage to achieve a desired speed

[aka_BigRed]

OK, here's a question for you guys:

My voltage sensor has a range of +1.5 to +10v and of course pH probe is centered at pH 7 = 0v. I was intending to use a MAX406 op-amp to invrease to a readable resolution, but can I shift the voltage up to the range readable by my sensor? I'd like to upshift voltage so that pH 0 is now +5.75v and ph < 7 gives voltages less than +5.75 instead of negative voltage as normally it would. Is that possible?

I'm not well versed in electronics & IC components, so I have no idea how to proceed. If anyone can help I could really use it.

I've got all my back work documented here with more info.
http://bytality.com/wrrc/index.cfm?task=display&doc=pH_Sensors

[sailfinreef]

you should be able to, you will have to alter your program for that, should be able to change the values in the program. what plc are you using, i might be able to smash something together for an example. do you have a touch pad or something that you are using to view the ph reading.

[aka_BigRed]

Originally posted by sailfinreef
you should be able to, you will have to alter your program for that, should be able to change the values in the program. what plc are you using, i might be able to smash something together for an example. do you have a touch pad or something that you are using to view the ph reading.

I'm actaully using a Dallas-Maxi 1-wire sensor (DS2438) with a WRT54g router running linx reading it. It's supposed to be used as a battery pack monitor so it's not designed to read neg voltage. I can easily correct for any voltage offset in my software, but I just need a magic circuit that shifts the mV's up so that 0mv is now about 383mbV. Will it work properly when the probe gives negative voltage? (ie neg probe voltage subtracts from 383mv and pos probe voltage adds to it)

[Osler@thesea]

You will need a Gain opamp followed by a Summing opamp. Somthing like this:

http://home.comcast.net/~jpbrowning2/ph_circuit.jpg

This circuit isn't perfect and I have not constructed it. However, it gives you the general idea. There are others in this forum who could fine-tune this circuit to do what you want to do.

I opted to use the Electrode Amplifier available from vernier (www.vernier.com) as it does exactly the same thing, shifting the voltage to the 0V to +5V range (Gain = 2.2V, Offset/Sum = 1.20V). Output is +0.408V to +1.992V (pH 0-14). This still presents a problem as your input is only +1V to +10V and a +1V ouput from the amplifier equates to a pH of 8.49. Therefore, you'll need an Offset/Sum of more like 2.0V.

HTH.

[sailfinreef]

I kinda misread your original question there but it looks like you got a real good answer, that is a good drawing.

[inerratum]

Bump, Anyone making any progress as far as Ph control goes? My project got sidelined until summer because of work deadlines and overtime.


Seth

[ronc98]

The circuit above will work fine. I have a similiar one that I constructed and tested for the last few months. I am wrapping up my controller and will more then likely offer it as a DIY type project. Pm me if anyone is interested.

R

[javajaws]

Originally posted by Osler@thesea
I opted to use the Electrode Amplifier available from vernier (www.vernier.com) as it does exactly the same thing, shifting the voltage to the 0V to +5V range (Gain = 2.2V, Offset/Sum = 1.20V). Output is +0.408V to +1.992V (pH 0-14). This still presents a problem as your input is only +1V to +10V and a +1V ouput from the amplifier equates to a pH of 8.49. Therefore, you'll need an Offset/Sum of more like 2.0V.

HTH.

How do you hook up the vernier electrode amplifier to the analog input. Do you have the pinouts of the amp? I'd like to try this approach since the DL06 has a 0-5v analog input module available.

- Jason

[Osler@thesea]

javajaws:

Here is the link to the pinout for the vernier stuff. Most probes can be ordered as DIN, but some only come in BTA.

http://www.vernier.com/probes/specs/pinout.html

They don't have wire colors, but I have taken one of their BTA connectors apart and the following applys:

Pin 1 (+/-10V input): yellow
Pin 2 (GND): black * (goes to DIN pin 5)
Pin 3 (Vres): green
Pin 4 (AutoID): brown
Pin 5 (+5V): orange* (goes to DIN pin 4)
Pin 6 (0-5V input): red* (goes to DIN pin 1)

* = these are the only ones you care about.

[aka_BigRed]

I've been out of it for a while, but had a couple Q's about the above schematic.

Can I substitute a MAX406 op-amp for both the above LM**** ops he used? I've got a couple lying around, plus Maxim will send you free samples so I'd like to prototype with Maxim parts if at all possible. That way if I toast a couple accidentally, I'm not really out much, and the 1-wire sensors the controller is based on is made by Maxim (Dallas Semi actually)

ronc98, can you post any differences between your circuit and this one? A schematic might be good for the general common knowledge.

[gabe21804]

Originally posted by inerratum
Bump, Anyone making any progress as far as Ph control goes? My project got sidelined until summer because of work deadlines and overtime.


Seth

My project has been also been sidelined til the end of june. Dealing with a state contract that has penalities involved, and most of my time has been devoted to this.

Ive got my tank up and running, the plc is doing basic functions timing, pumps, on and off cycles, temp cut offs...etc nothing advanced will be added til late june.

[ronc98]

I will post a schematic on monday of the whole thing. you guys can grab some ideas from it.

R

[Toast_Man]

Ok so I am being a bit lazy and am not reading through everything......this may have been mentioned already but there are soe really cool smart relays at www.klocknermoeller.com

i had to mess around with one of their EZ relays for a customer of mine and found that they were quite a nice little unit to work with.
I program PLC's for a living and have wanted to set something up on my tank to do automation for a long time but just haven't had the time or the $$ hats off to all of you guys who have taken the plunge!! :)

just a FYI for all you automation geeks :)

[ribs]

I'm going to start writing PLC code for my tank. I have accumulated the following hardware: AB SLC5/03, multiple I/O (contact and triacs), 4-20mA in, 0-10v out, panelview 550 (monochrome touch/keypad). I think I have the hardware down, hehe. Just have to get going on the code, then hook all my tank equipment up.
Those of you who have some logic built already, could you forward it along so I can get some tips on the features and functionality?
Code could be AB (preferably, even up to clogix is ok), but I can handle modicon, ge-fanuc, automationdirect, keyence, etc. I have most software packages, so I could probably read anything ya got, don't do seimens (but a "print to pdf" of the seimens would be ok)
Thanks!
When I come up with some logic I'll post it up for your critique :)

[RV8tor]

Hi
I have been taggn along for the last few months and I have been inspired to try this. I have just gotten the
Siemens Simatic S7-226 - P/N6ES7 216-2BD21-0XB0 - 85-264 VAC Supply - DI-24xDC24V - DI-16xRelay (2A). I also have a PPI cable. I will probably need help with the programming, just a basic one for now to do the normal stuff and then, maybe I can add on later.

First question is what else do I need as far as hardware? I would like to control: lights, moonlights, heaters, two external pumps, ph, orp. for now. I do have an electronic backgound but its been awhile.

Thanks in advance for the help and also thanks for all the info you have already posted.

.

[sailfinreef]

a thermalcouple mod. or a 4-20 input card with a transmitter for your temp and ph etc. some cube relays so you dont trash the relay cards. Im pretty fluent with the allen bradley plc 3 and5's so if you have any questions with some of the programing I could probably help you out.(if your not sure what chips do what or even ladder logic) I could write it up for you in trilogic which is basicly the same as ab code.

[RV8tor]

Thanks Sailfin I will probably take you up on your offer

[RV8tor]

For all you having troubles finding a PPI cable, there are two on ebay right now. Me, I am looking for a thermal couple, some "S word" and relays. anyone have any laying around please let me know. I am tring to keep this tread going now you all have me hooked.

[Steelslinger75]

What are you guys using for a pH monitor that will tie into the Analog Input? I have all ao my hardware ready to go for complete reef control except for a pH monitor.

[marm64]

I am starting to set up a controller for my system and was wondering what to use for a temp probe? I have a 0-10 volt input to work with. I did some searching but did not want to buy somehting that would not work.

Thanks

[ribs]

OK, back at it.....
This weekend I'm going to try to get the lights working via PLC (AB), will post some prelim. ladder logic after I debug it a bit more, and will be looking for some comments/feedback.
Have fun :)

RV8tor - My employer was recently awarded a project using an S7 series PLC, the software is in, just haven't started on it yet. I should be pretty familiar with the specifics of the S7 in short order. I did use an S5 series, but that was a bunch of years ago.

[tide_ben]

Originally posted by marm64
I am starting to set up a controller for my system and was wondering what to use for a temp probe? I have a 0-10 volt input to work with. I did some searching but did not want to buy somehting that would not work.

Thanks

Check out http://www.omega.com/. They have quite a bit of process control equipment for a decent price. They also send you cool Dilbert cards with your order... :rollface:

[cduran02]

Originally posted by tide_ben
Check out http://www.omega.com/. They have quite a bit of process control equipment for a decent price. They also send you cool Dilbert cards with your order... :rollface:

You could get the thermistors at Omega, I actually have one of their temp controllers with a thermocouple. The problem with using a thermocouple with your own controller is that you would also need to get a cold junction wich adds to the cost. The reason you need a cold junction is to compensate for the difference in materials between the thermocouples wires and the connector on your controller. With thermistors you dont have that problem and they work well for the temps we are dealing with.

[slug]

Would you really need the accuracy of cold junction correction? With the temperature swing inside your house you'd probably only be correcting a hundreth of a dagree.

[WY_REEFER]

I would use an RTD for temp, more acurate than a T.C.

I am glad to see someone else interested in this. I have been working on automating my 180 gallon for a while.

I am using a Allen Bradley PLC. I have a
foxborro PH and Cond. transmiter. I have wrote a program that I will enter sunrise and moon rise times for the whole year, and it will simulate a natural reef within a min. I am now working on getting a always on internet conection so I will be able to use remote desktop to monitor and control my aquarium from anywhere.

[WY_REEFER]

Here is a temp transmitter that would work good.
http://www.omega.com/ppt/pptsc.asp?ref=TX250&Nav=temn03

You can change 4-20 mA to 1-5 volt with a 250 ohm resistor.

Then you just scale your PLC to read 1-5 volt.

Here is an RTD that would work good with that transmitter.
http://www.omega.com/ppt/pptsc.asp?ref=PR-10&Nav=temc03

Or keep your eyes on ebay for a cheaper one.

[cduran02]

Originally posted by slug
Would you really need the accuracy of cold junction correction? With the temperature swing inside your house you'd probably only be correcting a hundreth of a dagree.

Actually I wouldnt use the cold junction for accuracy. More for stability of the reading. Ive tried getting readings without using a cold junction, and I could never get a stable voltage from the TC.

[cduran02]

I was going to originally try out a PLC, never had a chance to work with one yet. But I designed a controller for a well monitoring system (for a work project) so I figured Id just use that.

[RV8tor]

yea!!

I thought this thread was going to die. Glad it isn't.

RIBS - Thanks for keeping me in mind, I know zero about this PLC biz, but want to learn for the tanks sake.

I am still searching for S/W for the S7 series that I don't have to pay an arm and leg for.

[WY_REEFER]

I have used trilogi PLC's before they are cheap, work very well, come with all the programing software, has a built in simulator, and have a HMI that is very easy to program.

Check this web site out:
http://www.tri-plc.com/t100mx.htm

[Donw]

Originally posted by WY_REEFER
Here is a temp transmitter that would work good.
http://www.omega.com/ppt/pptsc.asp?ref=TX250&Nav=temn03

You can change 4-20 mA to 1-5 volt with a 250 ohm resistor.

Then you just scale your PLC to read 1-5 volt.

Here is an RTD that would work good with that transmitter.
http://www.omega.com/ppt/pptsc.asp?ref=PR-10&Nav=temc03

Or keep your eyes on ebay for a cheaper one.

Saw this post, just wondering if you can explain how and where to add the 250ohm resistor. Ive been searching for a way to get 1-5v scalable voltage from a ph transmitter that sends 4-20ma. My controller will only use 1-5v.

Thanks
Don

[ribs]

Placed across (parallel with) the 4-20ma terminals.....
"piggybacked"

[cduran02]

Omega also has pre-amplified electrodes, they dont need the high impedance input, you just need something that can read down to the mV. http://www.omega.com/ppt/pptsc.asp?ref=PHE6300_5300_2114_1304&Nav=grecc05

[ribs]

I agree with recent thread comments about this being nice to have some active participation here with thread watchers hopping in and stuff.

[Donw]

Originally posted by ribs
Placed across (parallel with) the 4-20ma terminals.....
"piggybacked"

Thanks,
I also found a article explaining the how and why.
Here is my latest automation remodel just getting started.
www.home.earthlink.net\~dwacker\automation.mht

Thanks again
Don

[cduran02]

Originally posted by Donw
Thanks,
I also found a article explaining the how and why.
Here is my latest automation remodel just getting started.
www.home.earthlink.net\~dwacker\automation.mht

Thanks again
Don

You have a typo in the extension to your .htm file, you have it as .mht

[WY_REEFER]

Here a diagram if you still need one.
Just FYI you can put multiple 250 ohm resistors in series and get 1-5 off of each of those if you need multiple outputs from a single loop.

http://photobucket.com/albums/b124/wy_reefer/?action=view&current=loopdiagram1-5volt.jpg

[WY_REEFER]

Don,
checked out your web site looks good.
I have plans very simalar to that.

I wonder if you could slurry the salt so you could mix it with a pump to your RO water?

I read somewhere that if you go to high in salinity it will mess things up is this true?

[Donw]

Originally posted by cduran02
You have a typo in the extension to your .htm file, you have it as .mht

.mht is a web page made by powerpoint. Will display as powerpoint presentation.

Don

[cduran02]

ah ok, no wonder it didnt open in Opera, Ill try with IE.

[gogatsbj]

I use a Honeywell UDC3000 PID for temp control with a K thermocouple and a Idec Smart Relay PLC. Idec has the a great GUI for logic and will pretty much do anything you need to do with a tank

[ribs]

Did you get the UDC3000 free? Can I have one? LOL
Pricey option for home reef temperature control, nice!

[Mr.Biggs]

any updates on projects?

[perpetual98]

I'm going to drag this thread up from the dead. Any new updates? I'm starting to work with a PLC and am just getting into the temperature/pH/ORP control hard of the hardware and I'm already lost.

Eric

[bink]

here in about 2 weeks Ill be building the panel for my reef controller of stuff Ive collected over the past several months.

What I have collected so far...

allen bradley pico gfx with lcd.. 8 dc inputs 2 of which can be analog with 4 relay outputs(free)

about 6 pieces of 6" wire duct panduit samples

allen bradley 24vdc power supply(free)

24vdc contactors(free)]

omega.com thermocouple with a 4-20ma output(free)...found it laying on the ground at the local toyota plant one day still in the box(works fine) fell out of a contractors golf cart prolly

picosoft pro software

hoffman 24x12 nema 12 enclosure - 20 bucks with back plate

4 illuminated led push buttons

4 led pilot lights

still looking for the ph sensor(need to search omega.com some more)

bunch of terminal blocks


to hook the pumps/llights up to this I plan on mounting handy boxes with receptacles in them to the bottom of the enclosure. The receptacles will be controlled by the contactors which are switched by the relay outs.

All of my lighting should be in here this week, meaning I will have all my aquarium done within 2 weeks. After that I will begin on the controls.

I just have a 55 gallon with a 20 gallon rubbermaid container collecting the overflow which feeds my skimmer. Skimmer feeds a 10 gallon refug which has a return pump in it. So controllin the levels can get irritating sometimes


Im not a fan of Solid State stuff because of heat issues and cost. For this application I think SSR stuff is pointless. I dont need the switching speeds and dont give a crap if I hear a miniature contactor pull in and out sometimes... :)

[FuzzyLogic]

Bink, can you give us more info on the TC? Any specs?