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View Full Version : Rapid ReefKeeper2 Temperature Fluctuation


ppurcell
01/30/2007, 07:06 PM
I setup my brand new RK2 last night and the temp reading constantly fluctuates about 30-40 times per minute. This results in my heaters turning on and off at the same frequency.

I sent an email to Digital Aquatics and got this answer:

A: "Here's the story with the heater. The jumping is due to the temp being right on the edge. The on/off of the heater is designed to function that way to hold the temp of the system so tight. Things you can do to help reduce this affect, make sure your probe is upstream of the heater. That will help reduce the rapid swings. Also make sure the two aren't close in the system. Also make sure you're not powering the heater on channels 4 or 8, they are relays and you'll hear a lot of clicking. This type of behavior is fine for a resistive element such as a heater and allows us to maintain very tight temp control with the RK2."

This doesn't seem "normal" to me as the temp reading should stabilize and not attempt straddle two values.

Not quite satified with the first answer; here is my follow-up question and DA's reply:

Q: The more I think about it the less it seems "ok" to have the controller continually straddling two temperatures and as a result cycling the heaters on and off 30-40 times a minute. This seems like it would be hard on the controller, the heater and my piece of mind. Even if it isn't damaging anything, it is just plain annoying to look at the controller and see the temp reading continually changing and the lights controlling the heaters blinking on and off.

A: "Heater are resistive elements and as such the best way to control them is with a pulsing duty cycle as we do. Again it ensures the tightest temp control on the market. It's the way we run it on several thousand ReefKeeper that have been on the market for years without issue. I assure you it's what I run and my tank and I have not one worry or concern!

You could take a black pen to the LED if you don't like the blinking. I personal like to see that it's doing it's job as intended."

Is it just me, or does this seem like normal behavior for a controller? Do other folks RK2's, AC Jr's, II's, III's, Aquacontrollers, etc. behave the same way? Of course, I am much more interested in how RK2's normally behave, but it would be interesting to know if other controllers are equally spastic.

tatoofr
01/30/2007, 07:32 PM
You could take a black pen to the LED if you don't like the blinking. I personal like to see that it's doing it's job as intended.

That;s funny,,

ppurcell
01/30/2007, 07:45 PM
Funny might be my reaction too, if I hadn't just spent over $325 on the pretty blinking lights.

Fish'InMN
01/30/2007, 07:49 PM
On a more constructive note, he or she is completely correct about the pulsing. Long-term, low-power LED circuits are created by pulsing the LED just rapidly enough to appear as a solid light to the human eye; this reduces the power consumption dramatically. The same effect could no doubt be used with heaters, I have no technical knowledge of heater elements though.

It does sound like the controller is doing exactly as it was intended, keeping a very tight control on the temperature of your system.

Cheers,
Marty

PS. I'm looking at a controller system as well when my tax refund arrives. Would you otherwise recommend the RK2? I realize you've only a small amount of experience with it so far, but any insight is helpful.

lvpd186
01/30/2007, 07:51 PM
Mine does the same thing but I agree with Digital Aquatics. It doesn't bother me and it does hold the temp dead on. I would imagine that other controllers keep the temp the same way, they might not make it as obvious as a blinking light.

ppurcell
01/30/2007, 08:02 PM
I don't disagree with your points at all and actually the blinking light isn't what bothers me, rather the rapid changing on the LCD display seems unnecessary and distracting. I've never had a piece of electronics besides a multimeter that had the digitial reading change as rapidly and frequently as the display on the RK2 does.

Other than the heater control aspect of the controller, it seems to be a terrific device. It is very simple to setup and use. I would like it a lot better if it had data logging and a web interface, but that can be had on a Aquacontroller III, but at over double the cost.

beaniebeagle
01/30/2007, 09:00 PM
does the temperature control supposed to have an offset or range like that of the ACjr that i have

http://www.neptunesys.com/AquaControllerJr_3_2%2BSerial_web.pdf

that small range keeps the heater from turning off and on rapidly,

lvpd186
01/30/2007, 09:09 PM
You can set the RK2 a temp. range (you can even set an emergency temp. where the lights will turn off). I think the original post talked about when the low point is reached the RK2 turns the heater on and off while it keeps that setting; ie the fluctuating temp. cycles the heater on and off to maintain the minimum heat, but once it is reached it tries to turn off the heater. Since each one of the channels have an LED light to show when the channel is on the light blinks on and off. At the same time the temp. reading in the display changes to show the current temp. I have to say my RK2 keeps my temp. right at 78deg. I have only seen it go between 78.1 and 78.2 (my tank is in the basement so the ambient temp stays fairly cool).

ppurcell
01/30/2007, 09:15 PM
lvpd186, I'm not sure I follow you. My RK2 does not have a temperature range on the heater control; only a cut-off temperature. If it supported a range, then this problem could be avoided by simply putting in a .2-.3 delta between the high and low temperature. That would fix the rapidly fluctuating reading, but it would stop the heaters from being turned off and on so frequently.

I can't understand why anyone thinks it is important to maintain temperature stability to 0.1 degrees.

crumbletop
01/30/2007, 09:16 PM
Can you set the ON temp like .4 degrees below the OFF temp? Maybe that would stop the oscillation of the heater. My controller (AC Jr.) doesn't do that, although it might if I set things to a closer tolerance. Mine gives a smooth temperature reading. There is also a program statement that the AC Jr. has that can be used to essentially tell the heater "if you just turned off, then stay off for 10 minutes" which would help the overall on/off thing. During the winter, my heater comes on just a few times a day, and my temp fluctuates about .4 degrees. During the summer, my heater doesn't come on at all, and I get a fluctuation of about .6 degrees.

lvpd186
01/30/2007, 09:36 PM
Oops my bad. I looked at the user guide again and I was wrong. When you set up the unit you set the min. temp. If the temp falls below this number the heater is turned on. Then, on another channel, you set the temp where a chiller or fan would turn on. I guess the idea is that this creates the temp "range." Sorry for the confusion. As for the +-0.1 tolerance I see what you mean. Maybe if the temp only read out the temp with out the decimal point it wouldn't change as often.

Crumbletop - I like the idea of that program statement. One of the reasons I got the RK2 is it seemed easier not to have to use program statements, but I guess that would add some flexibility.

ppurcell
01/30/2007, 09:36 PM
Here is a link to two 30 second videos that shows what the controller is doing:

Low Res ReefKeeper 2 Heater Control Video (http://s172.photobucket.com/albums/w29/pgpurcell/?action=view&current=MOV01585.flv)

High Res ReefKeeper 2 Heater Control Video (http://s172.photobucket.com/albums/w29/pgpurcell/?action=view&current=MOV01587.flv)

Fish'InMN
01/30/2007, 10:09 PM
Ahh! That would annoy the heck out me as well!

I really don't know if there is any way to resolve it though, as any change would have to be software related most likely. You would need to change the display options so that the temperature is only updated once a second or maybe once every ten seconds.

Good luck!

tatoofr
01/31/2007, 06:22 AM
That would drive me crazy, does that mean the heater is going on and off like that?
I have the rk 1 , doesnt do that at all.

Frank

crumbletop
01/31/2007, 06:35 AM
Seems like it would be best if DA just changed the firmware to let you specify the on temp and off temp separately. I have mine set up to turn on at 78.6 and to turn off at 79.0.

elephen
01/31/2007, 07:14 AM
Wow that is weird, but a pretty blue blinking light :)

I have an ACIII and never once had an issue like that at all. It keeps the temp within 1 degree pretty well.

ppurcell
01/31/2007, 08:16 PM
So, here is what I learned today.

After the DA guy watched the video he stated that the controller is actually not doing what he thought it was. And suggested resetting it back to factory defaults.

Which I did and then noticed that the temperature became stable.

After reconfiguring everything back the way it was, the temp start to fluctuate again. One more reset, and then I configured each function seperately. It turns out that the problem is tied to the temperature calibration/compensation. After I adjust for the 1.2 degree difference between what the controller is measuring and what my three regular thermometers read, that seems to be the trigger for having the controller go wacky.

Now I'm waiting to find out what DA wants to do next...

Does anyone else have a RK2 and use the temperature calibration functionality?

ppurcell
02/01/2007, 12:14 PM
It looks like there maybe a bug in the temperature calibration code. The DA guy said he is looking into correcting the problem then posting a firmware update in the next couple of days.