Fermentation Chamber Help

[mnHawk8]

I’m having some problems with my fermentation chamber (an upright freezer, about 4.5 feet tall) build. I am using the BCS box to control heating and cooling cycles. The BCS is controlling two 10A SSRs. When I plug the freezer cord into the control box I built, the compressor will cycle on every 30 seconds or so (for about 3 seconds), but not at full power, and then turn back off; repeat. This happens when the process is not on. When I put the BCS in manual mode and turn that outlet/SSR on, the compressor turns on and runs like normal. It’s almost like the SSR is leaking enough power to slightly turn the compressor on every 30 seconds or so. Is that possible?

I wired the SSRs like post #3 in this link: http://www.homebrewtalk.com/f51/bcs-460 ... lp-143050/

I tried to follow this process logic: http://forum.embeddedcontrolconcepts.co ... ?f=6&t=287, but very well could have gotten something wrong either in the process or the system settings.

Anyone have some thoughts as to what I'm doing wrong?

[ECC]

Can you save your configuration to a file and attach it to this post? Go to the 'System Settings' page, and scroll down to 'Configuration File Save/Restore'. Then use the upload attachment feature of this forum. That way we can load your config onto our BCS and really step through the process.

Does the compressor turn on when you are in manual mode and all outputs are Direct Off?

I've never heard of SSRs leaking current, but I guess it could be possible that you have a bad SSR. It might be worth your time to swap your heat/cool and see if the problem follows the SSR.

[mnHawk8]

I'll post my config file this evening.

Yes I did plug it into each outlet and it does the same.

Thanks for your help.

[rcrabb22]

Until we see the config file my best guess would be you have the asserted output controlled by duty cycle or PID. For a compressor you would want Direct Control On/Off, or Differential Control with a temperature setpoint defined depending how you set up your state machine.

The other thought would be your temp sensor has large swings in temperature readings, as mine did before I did a better job of shielding the senor wire from compressor interference. See my post in General Discussion section of the forum, "Bouncing Temperatures"

A look at your data log would be helpful to see if that is the case.

I'm not an expert but someone here will be able to help

[mnHawk8]

I've attached my config file.

While I could very well have something set up wrong in my process, I'm not sure my problem has anything to do with my BCS box. I say that because before I had the BCS controller hooked up to my control box, I juiced it up and plugged a fan into it and had power leaking through even then (the fan blade would move VERY slowly).

[rcrabb22]

I think I see the problem. On the Add/Edit State machine page, State 3, you enable Out1 for cooling as differential control at 68F. You also enable out1 for Alternate PID control. PID's will cycle power on/off to attempt to not over or under shoot the target temp. For heating , that's usually OK, but for cooling, compressors can be damaged. They want to run continuous and when shut down need to rest so the pressure on the input and out side of the compressor will equalize. Disable Alternate PID for out1.

For good or bad you followed my attempt at 2 stage control and I have never implemented that process in my world yet. My example used direct control of the heating and cooling source outputs with On/Off control which defaults to 100% duty cycle. I let the state machine exit conditions control when to disable the asserted SSR and move to another state.

You enabled differential control. Under Systems Settings you set differential for Out0 (heat) and Out1 (cool) to 2 degrees which means +/- 1 degree from the set point.

State 1 says to goto State 2 (heat temp) when temp0 is <= 68F. In State 2 you enable differential control with a set point at 70. I think Exit Condition 0 supersedes the differential as it says to goto State 0 when temp is 70F.

Same is true for State 3. Differential set point is 68F and Exit Condition 0 says to goto State 0 when temp is 68F.

My advice would be to change control of out0 and out1 to Directly Controlled On/Off, Duty Cycle to 100%, disable Alternate PID control from both out0 and out1 and give it a go.

[mnHawk8]

Thanks rcrabb22. I think I made the changes as you described but am still having the same problem with the compressor. I've attached the updated config file.

When I go into manual mode I can get the compressor to completely turn on; it's just when I turn manual mode off that the compressor won't completely turn off.

[rcrabb22]

I out of ideas right now and I have to get to bed, early day tomorrow. Try another run and show us the data log so we can see a different perspective. Maybe ECC can see something I'm not

[ECC]

Everything looks good in the new config file. I agree with you that from your description, it sounds like the problem is most likely electrical. The wiring diagram that you point to looks correct. Can you measure the DC voltage between terminals 4 and 3, the SSR control terminals? This should read 5vdc when ON (use manual mode), and 0vdc when OFF. If it doesn't read 0vdc, I would check the control side wiring. Terminal 3 (+) should go to the BCS Output, and terminal 4 (-) should go to the BCS GND terminal.

What type of SSR's are you using? Do you have part numbers/datasheets? Another cause of this behavior would be if the SSR is not rated for the voltages being used. In the wiring diagram link, cyberbackpacker is using Auber 25A 90-480VAC rated SSRs,which would work for your 120VAC load.

Can you measure the AC voltage between the switched terminal of the SSR and neutral? That would be terminal 2 in the diagram.

ssr_wiring.jpg (24.58 KiB) Viewed 8197 times

I attached the diagram here for reference. Credit to cyberbackpacker, linked below.

[rcrabb22]

If the issue is electrical, why does the SSR stay active without pulse in manual mode but not while under BCS state machine logic control? Just curious what the difference is between manual mode and logic control.

EDIT - My bad, I didn't fully understand the issue, re-read OP - cycles compressor when process is NOT active. <RED FACE>