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Unread 01/04/2009, 05:42 PM   #1
oldsaltman
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Latching relay for ATO diagram?

I am looking to improve my ATO as I upgrade. The one I made years ago fills from the low setting of my two float switches. I want to change it so I have some time between the ATO refilling the sump. I searched all day and found a number of “latching relay” type designs. I found this that appears to work for what I want. Can anyone look at this diagram and see why it would not work as advertised?




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Unread 01/04/2009, 09:02 PM   #2
spamreefnew
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it looks like both switches would need to close befor anything could happen in this diagram....what is it you are trying to do???


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Unread 01/04/2009, 09:37 PM   #3
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Unread 01/04/2009, 09:37 PM   #4
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That may help you better understand....


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Unread 01/04/2009, 09:44 PM   #5
AusWog
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the 2 float switches have to be in for the coil to latch... is that a safety feature?and the 2 contacts on one side which connect together are both positive. im pretty sure this is a double throw relay, which means there are 2 different sides that are isolated from each other but switched at the same time. if its only switching a solenoid ,which it seems you only are, after the float switches are on and they come to the other side of the relay ( no and c) they dont need to be there and it will work the same...they really do nothing.

how is this intended to be used? it makes a parrellel'ed feed circuit to the relay coil which is..usless...when you say you want time as in a timed circuit?


the only way i can see this working is IF the 'no' terminal is put into the 'nc' terminal AND you run a second feed wire to the lower switch from the 12vdc + and remove the bridge between the 2 switches so they are switched seperatly.


or like this


this allows : incase first switch gets stuck, the second will still give the relay power.

its the only sense i can make out of it...


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Unread 01/04/2009, 10:09 PM   #6
BeanAnimal
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Auswog, if you look at the circuit again, it is a latch just like the one I posted. The annimation should help you understand how it works.

As the water in the tank drops, the top float closes but the bottom float is still open, so nothing happens. Once the water level falls enough, the bottom float also closes and actuates the relay coil. At the same time the NO and C contacts on the 12V side of the relay close. As the tank fills the bottom float opens but the relay coil still gets power through the "latch" formed by the NO and C contacts. The relay stays energized until the water rises enough so that the top float opens.

It may be a good idea to change the image at photobucket so that a bad circuit is not on display


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Unread 01/04/2009, 11:13 PM   #7
therealfatman
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Bean it is fine that your drawing, antimated and all, shows how it works but why do you not show a true wiring diagram to go with that depiction. In that I mean show the standard eight connection terminals that would be on the relay and show those connections in relation to lines, loads and float connections. That would be what would make things simple and understandable when taken in conjunction with your drawing. Also pick some color conventions and stick to them.

Personally I had a hard time figuring out your drawing meant or why it was drawn as it was. It took a while to realise that the box designated as K was the coil. I imagine most people will not comprehend what the drawing really means. Most people are more interested in how to wire something rather than than why it works. Nothing personal, but very few people know how electricity is produced or transported, stepped up or down, they just care that the light switch when flipped causes the light to come on.

Typically most peoples eyes sorta just glaze over when electrical circuits are discussed. Even other engineers seldom have technical discussions with electrical engineers. Typically we just except what they say and are glad we do not have to know what they know or do what they do. A course in electrical circuitry is not even a requirement to obtain a degree in other fields of engineering, it is a seldom chosen elective. To most engineers electrical engineering is even less understood than chemistry. Therefore I doubt the average reef keeper iss adept at circuitry. IMO

Also strange as it may seem to you, I had never even heard of the term latching relay until I saw it used in this forum. Magnetic relay, coil relay, but never before latching relay. That term does produce results on Google though, but it is always in addition to the more common term of magnetic relay that distinguishs it as different from the solid state non magnetic coil relay.



Last edited by therealfatman; 01/04/2009 at 11:34 PM.
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Unread 01/05/2009, 07:09 AM   #8
oldsaltman
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Bean, I saw your animation and kept tring get it in my head how the relay was wired. The diagram I was just one that I found and that I could understand the relay. Are you saying the relay cannot be wired as drawn?


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Unread 01/05/2009, 08:17 AM   #9
BeanAnimal
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Quote:
Originally posted by therealfatman
Bean it is fine that your drawing, antimated and all, shows how it works but why do you not show a true wiring diagram to go with that depiction.
What I posted was a schematic, not a wiring diagram. A schematic shows the circuit in its electrical form and is a universal means of communicating circuits. No different than a hydraulic schematic or plumbing schematic.

Quote:
In that I mean show the standard eight connection terminals that would be on the relay and show those connections in relation to lines, loads and float connections. That would be what would make things simple and understandable when taken in conjunction with your drawing. Also pick some color conventions and stick to them.
There are many "standard" relay terminal configurations. That is why a schematic was presented and NOT a wiring diagram. Take the panel off of your dishwasher, furnace, etc. It will have a schematic, not a wiring diagram

Quote:
Personally I had a hard time figuring out your drawing meant or why it was drawn as it was. It took a while to realise that the box designated as K was the coil. I imagine most people will not comprehend what the drawing really means. Most people are more interested in how to wire something rather than than why it works.
"K" is the universal schematic designator for RELAY. The graphic symbol used is one of several recognized to represent a double pole relay. Frankly, anybody who endeavors to build an electronics circuit needs to take the time to understand HOW and WHY the circuit works. Part of that understanding is figuring out how to read a schematic.

Quote:
Nothing personal, but very few people know how electricity is produced or transported, stepped up or down, they just care that the light switch when flipped causes the light to come on.
Yes, and they should hire somebody to wire the switch so that it works when flipped. If they want to DIY, especially with electricity, then they need to invest the time to understand WHAT they DIYing and how it works. Safety in a project like this is derived through understanding.

Quote:
Also strange as it may seem to you, I had never even heard of the term latching relay until I saw it used in this forum. Magnetic relay, coil relay, but never before latching relay. That term does produce results on Google though, but it is always in addition to the more common term of magnetic relay that distinguishs it as different from the solid state non magnetic coil relay.
I think you are still a bit confused

Latching circuits are circuits that "latch" or prevent themselves from collapse when their trigger is removed. The term "latch" is key just like a "latch" on a mechanical device. A "magnetic" or "solid state" device can be used.

The "latching relay circuit" is one of the oldest and most common forms of electrical circuit in use. Until the advent of microprocessors, every elevator on the planet used dozens (hundreds) of interconnected "latching relay circuits" to operate. The relays are used to form a "Finite State Machine" and hold the chosen state until the next state is selected (button press or door opening). Where did "finite state machines" come from? Alan Turing (the father of computing).

In any case, if you look into "relay logic" or "ladder logic" you will find that the "latch" is the basis for the very code that drives PLCs and even modern computers. So you may have never heard or used the term "latching relay circuit" but it is present in almost every aspect of your life.

Be aware that you can buy "Latching Relays" that have the "latch circuit" built into them. When actuated, they "stay" actuated until a second signal tells them otherwise. Same idea, but no external wiring, it is all in the "box".


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Unread 01/05/2009, 08:19 AM   #10
BeanAnimal
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Quote:
Originally posted by oldsaltman
Bean, I saw your animation and kept tring get it in my head how the relay was wired. The diagram I was just one that I found and that I could understand the relay. Are you saying the relay cannot be wired as drawn?
The relay wiring diagram and my schematic are both the same thing

As long as the relay you buy has the same pin configuration as the drawing, you will be fine. If it does not then you have to use your noodle and adapt the wiring diagram to the new relay (with help of the schematic).

Hope that helps


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Unread 01/05/2009, 08:38 AM   #11
oldsaltman
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OK, I got it now! Thanks


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Unread 01/05/2009, 11:52 AM   #12
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Or, you could do what I did.

I only have 2 floats in my sump, I want the upper float as an emergency shut off. Not ATO main shut off. What I doid was get an Omron HC3R-A timer. Now, the lower float is set to turn on when the level drops, and the upper float turns OFF when level to high. I wired them in series. Wire the power of the Timer through the floats. Timer is set for 10 minutes. The float, as you all know, will click on/off alot when right at the switch level. This is due to the little waves and such in the sump. It's unavoidable. The lower float has to remain ON un interupted for the timers setting(10 Min) then the pump kicks on. This makes sure the level is low enough that the float is not just bobbing. Once the level reaches lower float,, it opens(shuts off power) to the timer, which turns off the pump.

No nusance turing on/off of pump, Still retains the High level emerg shutdown float, for if the main float gets stuck. If sump level goes low due to maintenance/cleaning sump. The ATO will not kick on for 10 minutes(could be set longer if desired). My top off water is halfway across the house, and the wife was getting tired of packing water every day when I'm out of town. I built this sys so to be pretty much fool proof. As long as the top off water is kept full, sys will run flawwlessly.


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Unread 01/05/2009, 12:23 PM   #13
oldsaltman
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Thanks, my ATO has also been working fine for a few years. I just wanted to add the ability to have the ATO pump only come on every few hours or so. My system refields a few ML every few minutes now. I just like the latching relay system with no timers involved.


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Unread 01/05/2009, 02:37 PM   #14
oldsaltman
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Bean, thanks again I took the diagram, my float switches etc and put it all out on the table to test. It works just as it should. Thanks


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Unread 01/05/2009, 02:52 PM   #15
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Not a problem my friend... and you learned a bit in the process


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Unread 01/05/2009, 05:49 PM   #16
THE ROOK
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By "latching" it seems you are effictively removing the safety feature from most dual float a.t.o's. Could this type of system utilize a 3rd float switch in case the upper float fails? If so, how would we wire that in?


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Unread 01/05/2009, 05:55 PM   #17
oldsaltman
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Bean, my current ATO only has one float switch level and a timer turn that off for an hour each day so I can do an automated water change. That way my timers/pumps can draw out 1g – 1.5g of old water and replace it with the same amount of new saltwater. The one float switch insures that whatever comes out is the same amount that goes back in. With the two switches the sump level will vary at any given time, so my previous design want work. Could this design be modified so that at some given time once every day when the water level is at its high level a timer/relay would know to turn the ATO off for a set amount of time? If that makes any sense?


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Unread 01/05/2009, 06:26 PM   #18
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Quote:
Originally posted by THE ROOK
By "latching" it seems you are effictively removing the safety feature from most dual float a.t.o's. Could this type of system utilize a 3rd float switch in case the upper float fails? If so, how would we wire that in?
In series with the TOP float.

The setup is actually much safer, even without the (3rd) emergency float. Why? The reed switches in the floats will only cycle (arc) once per fill when used in a LATCH type circuit. When used as straight unlatched switches, they are subjected to tens of thousands more times (arcs) and therefore are at a much greater risk of failure.


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Unread 01/05/2009, 06:30 PM   #19
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Quote:
Originally posted by oldsaltman
Bean, my current ATO only has one float switch level and a timer turn that off for an hour each day so I can do an automated water change. That way my timers/pumps can draw out 1g – 1.5g of old water and replace it with the same amount of new saltwater. The one float switch insures that whatever comes out is the same amount that goes back in. With the two switches the sump level will vary at any given time, so my previous design want work. Could this design be modified so that at some given time once every day when the water level is at its high level a timer/relay would know to turn the ATO off for a set amount of time? If that makes any sense?
Sure, you would just use a relay on your timers output. The NC contacts would be the TOP-OFF power and the NO contacts the water change power. That way, when the water change kick in, the ATO is not powered and vice versa.


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Unread 01/05/2009, 07:13 PM   #20
oldsaltman
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OK, I can see that that would work if I had two pumps running at the same time moving the same amount of water in and out, but my previous design simply turns off the ATO, draws off 1g of waste water, and then refields the sump to it's normal heigth. The latching relay system will cause the water in the sump to be at different levels at any given time. I would need to be able to turn the ATO off once daily when the water level is at it high point to accomplish this type water change.


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Unread 01/06/2009, 07:22 AM   #21
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OK, I know how to do it now. A timer that only turns on once a day at your preset time. That controls a relay that is wired in series with the bottom float switch. When the relay closes it would be the same as the lower float switch causing the main relay to latch and force the ATO to fill the sump to the level of the top switch. Then the other timer could cut the ATO off for 30 minutes or so. That would allow for my water change system to work again because it would maintain the sump at a constant level during the water change!


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Unread 01/06/2009, 09:20 AM   #22
banditpowdercoat
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I'm curious on your auto waterchange setup. Do you use 2 pumps for that and separate float switches? One pump to take old water out, and another to pump fresh in?


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Unread 01/06/2009, 09:58 AM   #23
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Bean, what if FS2 fails ( remain close)? Thanks.


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Unread 01/06/2009, 10:11 AM   #24
banditpowdercoat
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if float fails, usually flood. Like with everything regarding our tanks, nothing is without periodic checking/cleaning. Problem with automation is, something WILL fail. My career is making things more automated. Sawmills, Mines, Factories, etc. Allways need some level of maintenance/equipment checking


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Unread 01/06/2009, 10:21 AM   #25
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Re: Latching relay for ATO diagram?

I am by no means a electronic guru. However, based on your diagram, it should work. I can't see why it wouldn't.

The diagram by AusWOG seems incorrect to me.

Quote:
Originally posted by oldsaltman
I am looking to improve my ATO as I upgrade. The one I made years ago fills from the low setting of my two float switches. I want to change it so I have some time between the ATO refilling the sump. I searched all day and found a number of “latching relay” type designs. I found this that appears to work for what I want. Can anyone look at this diagram and see why it would not work as advertised?




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