Temperature Control Box Build

[Loetz]

Ok, so I'm back to work on my temperature control box. I came up with a wiring diagram today that I would like you guys to review for me.

On the top of the box will be two inlets that connect to two different 15 amp mains. This is where the power will come in.
On the sides of the boxes, just below the inlets, will be the corresponding power outlets.
PID 1 and PID 3 are controlling the two SSRs while PID 2 is just serving as a thermometer.
I plan to connect the probes to the box using XLR connections on the sides and closer to the bottom of the box.

It still looks basically the same as the last time I posted it in a thread. I'm still planning on putting plexiglass over the SSRs and the open space in the middle, so please don't freak out.

Does this wiring diagram look ok to you guys? Is there anything I'm missing? Do I need to ground the PID controls?

 

[Loetz]

...and I'm right in thinking that I can't use this thing to regulate a refrigerator, right? I just want to make sure.

 

[bobsbeer]

I don't see why not if you have one PID & SSR to control the cooling and another to control a heat source. But I'm sure there must be an easier way.

 

[jamesb]

Don't use a PID and SSR to control a fridge compressor, you'll break it.

 

[Wild Woods]

Don't use a PID and SSR to control a fridge compressor, you'll break it.

Why will a PID and SSR break the fridge compressor?

I'm building a control unit for my Fermentation fridge and was going to use SSR's so I can use the same unit when I move onto AG and need boiler control.

 

[Vossy1]

Why will a PID and SSR break the fridge compressor?

Fridge compressors are not designed to be switched on/off to frequently :thumb:
IIRC you can use a PID to control a fridge by using the alarm relay output (James can confirm/deny) but the 'issue' of fequency of switching will still be a problem unless you can set parameters for the alarm 'range'.

 

[Loetz]

Yea, I figured that it was a bad idea. Even if it would work, it seems like it would waste a lot of energy.

So what about the wire diagram? Does that look pretty sound? Do I need to ground those PIDs?

 

[Loetz]

Now I just need to remember what all of these contacts on the back of the PIDs are for...

 

[Loetz]

So here is the wired box. The SSRs will be connected when the box is closed. Any thoughts on this? Is it going to catch on fire if I turn it on?

The two wires on the top left are the power.
The two wires on the bottom left are for the SSR.
The three wires on the bottom right are from the probes.

Honestly I don't know which probe wire goes where. The probe has a green wire with a blue tip, a black wire with a yellow tip, and a red wire with a red tip and a little white sleeve that says PT100.

I'm going to connect it this way and hope it works:
8 - red tip
9 (-) - yellow tip
10 (+) - blue tip

EDIT: This seems to have worked.

I'm not happy with the exposed copper on that black wire either. Do you guys think it will be ok?

 

[Vossy1]

Not been on the forum much, so I haven't seen your posts L, it looks like you're making good progress though

So what about the wire diagram? Does that look pretty sound? Do I need to ground those PIDs?

I'm no electrician, but to my eye all looks good to me, and no the PIDS don't need grounding.

Is it going to catch on fire if I turn it on?

I doubt it but I'd keep an eye on how hot those SSR's get in use for the first few outings.

I'm not happy with the exposed copper on that black wire either. Do you guys think it will be ok?

It would be better enclosed and as there's also some exposed copper on the wire next to it...thinking arcing :hmm:

Would someone that knows the REX-C100 please check the way I wired it?

I'm not familiar with them, sorry...could you post up a wiring diagram for one.

 

[Loetz]

Not been on the forum much, so I haven't seen your posts L, it looks like you're making good progress though

Would someone that knows the REX-C100 please check the way I wired it?

I'm not familiar with them, sorry...could you post up a wiring diagram for one.

Well, you wouldn't have time to take a look at my recipe problem now would you? :whistle:
http://www.thehomebrewforum.co.uk/viewtopic.php?f=36&t=23246&p=229120#p229120

There's a nice wiring diagram on the side of the PID, but the box is all closed up at this point. I'm just going to hope that it works. If it doesn't, I suppose I'll have to resolder the XLR connections on the probes.

It powers up fine, but it just reads 24 over 100. Lets hope that it works normally after I program the PIDs for PT100 probes etc.

 

[Loetz]

I changed the probe type to PT100, but that is it. Are there any other settings I should change?

The two PIDs on the right seem to be fairly in sync, but sometimes they vary by .3 degrees.
The PID on the left is always reading about 1 degree lower than the two on the right.
Is there some way to calibrate the probes on these things?

Any ideas?

You might not see it at first glance, but there is a sheet of plexiglass covering the middle. The power tools really did a number on it in a few places, but I guess that's ok. It's not going to be a beautiful box.

 

[bewbrew]

Hi. To calibrate the probes you will need to immerse probes in ice water to check if they read 0 deg c on the pid.
If the reading is out you can alter the offset of the pid by pressing the set button for three seconds to enter setting mode.
When display alters to show AL1 press set key a number of times until you see SC on the display. This is PV input value adjustment,
by pressing up or down buttons you can set the offset value to match the difference that the pid showed.
Example! if the pid reads 2deg c in ice water you need to set the SC value to 2 then it will display 0 deg c .
You should really check the temperature reading at a temp near to what you will be using it eg 66deg. To do that you will need
a thermometer that is known to be accurate to compare readings. Again if the pid shows a different reading to the accueate thermometer reading, reset the SC input offset value by the difference.

I hope that all makes sense.

John

 

[Loetz]

Thanks! Do you think I should do the ice bath if I'm going to calibrate with another thermometer?

Are there any other settings I should consider changing?

 

[bewbrew]

No, just calibrating at a temperature near to what they will operating will be ok, providing your thermometer is known to be accurate.
All other settings are probably best left at factory defaults, except probe type of course. Remember when using Pt100 probes that the readings are to 0.1 of a degree so dont get too hung up over accuracy.
I think consistancy is the important factor when brewing, and this is what the PID's allow us to achieve. If you produce good beer and know what temps etc were, then you should be able to do it over and over.
Keeping accurate records of every brew you make is the important thing, then if the results are not as expected you can alter on the next brew.

 

[Loetz]

Hey, all:

It's been a while! It's starting to cool down enough to do another batch of beer, so I'm starting to tinker with my set-up.

I'm having a problem with the PV readings that I'm getting from my REX C100s. I'll set the SV to something like 66 and it will heat the water up to that level and the display will read as if it is holding a steady temp. Then I'll change the SV and instantly the PV temperature reading will change dramatically.

I made a video of this so you can see what I'm talking about.

http://youtu.be/kbVs1Bs1di8

I believe that the actual temperature of the water is somewhere close to 43 degrees C, but the reading fluctuates when I change the set value.

10.3° SV = 42.9° PV
20.3° SV = 42.9° PV
30.3° SV = 42.9° PV

Between 10-30°, I'm getting a consistent PV reading.

40.3° SV = 40.9 PV

When I hit 40° (close to the actual temperature, but a little under) the PV reading drops 2° .

50.5° SV = 42.9 PV

If I set the SV over the real reading, it goes back to reading the normal PV.


After that I demonstrate that the reading gets more and more off the closer I get to the real temperature reading.

33.3° SV = 42.8 PV
35.3° SV = 42.4 PV
37.3° SV = 41.9PV
39.3° SV = 41.5PV

Do you guys have any idea what is going on? Any help would be well appreciated.

 

[Fil]

most odd SV being the set value and PV being the present value?.. so PV is reading the current temp. and that changes with the SV value not the temp?? i too would be concerned and puzzled..

perhaps if your in the tuning mode? with my device its an option, it might be a default start mode for yours?

I have a sestos pid which came with a single sheet of info so dont know much about the rex ones. but I did find that the online manual for the auber pid very enlightening to the different parameters thier function and options.. While not all the auber options are available on the sestos unit (Farenheight display for example) the settings and options are extreamly similar... it may be of use to you?
http://auberins.com/images/Manual/Manua ... %203.4.pdf


AFAIK there are 3 control parameters the P I and D, which determine how the unit controls the temperature. you can set these yourself but the units have an auto tune mode which if set up in the conditions used for brewing ie your hlt with water out of the tap (and treated) will derive the optimum control parameters for your circumstances (hitting strike temp from cold).
This proceedure can take hours, perhaps more than twice as long as it would take to just heat up the water.. but when complete will automatically set your unit to optimal performance for its desired task.

If you want to use a controller for more than one task, you can set it up to auto tune in each circumstance and record the control parameters it derives and just plug them in each time you change function.

 

[mrlard]

Have you auto tuned them yet? Mine did this fresh out the pack but once auto tuned the problem disappeared.

 

[Loetz]

Hmm... Maybe I'm missing something. I have autotune turned on, but I didn't do anything special after that. I've let them run for a long time in the past... maybe an hour... and I was still having the same problem.


EDIT: Wait. I just went back and checked and autotune was off. I could have sworn I'd turned that on! Let's see what happens now.

 

[mrlard]

????

Auto tune you should turn on and run once so the pid can work out the best parameters. Once set it will turn off but all your values will be set.