Temp and pH Controller

[jd]

I have my controller set to turn the heater on at 78.5 and below so there is no high point to avoid swings. Tanks is always 78.5
If temperature reaches 80 fans kick on until temperature drops to 79.5 so have high and low point
If temperature reaches 82 lights shut off and wont turn back on unless I reset to signal tank temperature was breached

With temperature consistency is key. So if tank wants to naturally peak at 80 I would recommend setting heater to 80. A fluctuation of 4 degrees in 24 hour period is to much. Some may get it away with that however the fish and corals would do better with more stability.

Thanks for your input Brian. The 10* range was a poor choice on my part, i assume it would be more like 78-81 or the like. How much would you say your temp swings in a given day?

I don't really understand the your idea on the setpoints.... If it turns back off at 79 why isn't that the setpoint? What are you trying to do that 2 setpoints a few degrees apart can't?

The two set points are to allows people to fine tune their temps. You know that if have your heater turn on at 79 and off and 79.1 it will cycle on and off almost constantly. I guess I could have one set point and have heaters on at 1.5* below that and coolers on at 1.5* or something similar.

[lazylivin]

I am not sure how the reefkeeper controller I have does it but for the heater port it only gives you an on temperature. There is not a high setting. The tank temp is always, 24 hours a day 78.4 - 78.6. The only time it goes out of the range is if I manually turn on the frag tank lights while the display tank lights are on. I have seen in that case it go to 80 and the fan kick on.

Think of it like this Josh. The heater itself has its own built in thermostat. It is likely that it is cycling on and off with tolerance less then .5 degrees. We could test that, fill a bucket with water, stick a heater, small pump to circulate the water and a digital thermometer. Turn the heater temp above the ambient room temperature and see if the temp fluctuates.

[cyberwollf]

Brian, i understand joshs worry. You don't want your heater short cycling every few seconds to keep water within 0.01 degrees. There is some hysterisis needed to prevent that.  The more I think of it now unless you a super high watts to gallons ratio of heaters. The transition will be inherently slow. I bet we could get away with 0.5 degree setpoint.  Thanks for the RK input. Intresting design idea to simplefly user input. I'm sure they just take your input and setpoints +-0.2 or something close.

All these questions should be answered when we get a prototype all working. We'd be able to monitor the cycling frequency on all outputs and make adjustments as needed. I know I don't want a 10 degree temp swing with this thing on my tank

another idea I have been kicking around for what I care about in a temp controller. With 3 Normal heaters all set at 79 they keep my tank +-1 degree.  I don't know if I want the complexity or addiontional possible failure of an independent controller. What I'd really like is only a normally closed relay that would open to kill the heaters if they got stuck on, so it would prevent cooking the tank. And of course overtemp light shutdown etc. But leave the temp control up to the actual heaters. Anyone had a problem with a heater other and being stuck on?

[jd]

I'm sure they just take your input and setpoints +-0.2 or something close.

That is exactly what I think they do also.

I know I don't want a 10 degree temp swing with this thing on my tank

It was a poor example! It was just what they happened to  be when I wrote that!

But leave the temp control up to the actual heaters. Anyone had a problem with a heater other and being stuck on?

You trust your heater thermometers more than ours? I think the inherent problem with most heaters is, their temp sensor is very near the element. Unless your heater is in a very high flow area, this can effect its operation. Also, how do you expect anyone to use one of these the one of its developers doesn't even want to?! 

[lazylivin]

You are likely right that there is a inhernet +\- built in to the controller and he brand controller probrably handles it diffrently

[jd]

Yes, I'm not so much worried about the cycling of the heater as I am of the relay, and SCRs are expensive...

Maybe I should just get a RK and be done with it

[lazylivin]

Yours is going to be much cooler.

[cyberwollf]

I say just code up the +-0.2 and be done with it. Allows a user to only have to input one setpoint.

[jd]

Well, that frees up some more IO pins. I may do a .2 over set is one relay one and .4 over is another one. That way you could use fans for .2 over or turn your chiller on at .4. That'd save energy and wear and tear on chillers. How does that sound to everyone?

[cyberwollf]

Mine is bigger....

[jd]

Yeah... uh... mine is... uh... bluer..

[HUNGER]

looks good guys 

Mine is bigger....

[jd]

Wes and I spend the evening talking about phase detractors and stators. We also managed to take a peak inside of a Pin-Point pH monitor. You'll be angered to know that the pH and ORP probes only differ by what appears to be 1 part. Also, the designer at Pin-Point forgot the importance of protection diodes and the reason why you use sheilded cables. 

New temperature probes are on the way, and should yield much better results.

[UDJustin]

where did you get the pinpoint ph monitor from

[jd]

Wall_Tank loaned it to us. Thanks again Wall.

[cyberwollf]

You'll be angered to know that the pH and ORP probes only differ by what appears to be 1 part.

He meant the monitor, not the actually probe itself.  And yes, they just add a jumper/resistor and sell it as ORP. BTW VERY POOR craftsmanship.. As Josh said they have crap just soldered in that they apparntly forgot about.  And the whole purpose of using a shielded coax cable with BNC connectors is voided by the little wire that is jumpered from one side of the board DIRECTLY to the ADC pin...

[UDJustin]

I had a pinpoint ph controller but it got wet and while it still turns on the number read out makes no sense lol.

[jd]

I had a pinpoint ph controller but it got wet and while it still turns on the number read out makes no sense lol.

Do you still have it?

[slandis3]

Do you still have it?

I have it at my house. I can bring it to the meeting so you can look at it.

[jd]

I have it at my house. I can bring it to the meeting so you can look at it.

If you (or Justin) have written it off as dead. I'd love to take it all apart and reverse engineer the circuit.

[Wall_Tank]

If you (or Justin) have written it off as dead. I'd love to take it all apart and reverse engineer the circuit.

Or at lease reverse engineer what not to do.

[jd]

Or at lease reverse engineer what not to do.

Heh, no kidding. That seems to me likely. They do a few things that I'd like to find the reasoning behind.

[jd]

Any by this week you mean the end of the month?? lol  Man, this project is actually super simple.. we are just lazy lol

did you ever figure out if we can burn arudino to a chip without the overhead of usb and all the other crap on a arudino board?

The USB section is a small part of our overhead, we have to use it because it includes all the delay, acd and lcd protocols.


See if you think this will work, I can't tell if it will do +/-2V or not. Its a shame the one I found yesterday is so dang small.

http://ww1.microchip.com/downloads/en/DeviceDoc/21409b.pdf

[cyberwollf]

im not familar with the design.  from wiki:

A Sigma-Delta ADC (also known as a Delta-Sigma ADC) oversamples the desired signal by a large factor and filters the desired signal band. Generally a smaller number of bits than required are converted using a Flash ADC after the Filter. The resulting signal, along with the error generated by the discrete levels of the Flash, is fed back and subtracted from the input to the filter. This negative feedback has the effect of noise shaping the error due to the Flash so that it does not appear in the desired signal frequencies. A digital filter (decimation filter) follows the ADC which reduces the sampling rate, filters off unwanted noise signal and increases the resolution of the output. (sigma-delta modulation, also called delta-sigma modulation)

[jd]

You totally dodged my question I'm reading a new datasheet now, it looks promising.