Hacked my CPE2 Plus

I got a wild hair to modify my CPE2 Plus. Not that it was terrible but the mechanical thermostat would dwell a couple to few degrees. I decide to try and shoehorn a digital temperature controller into it. I had to think about it a bit because it it a one way ride. After collecting all the bits, I decide it was a go.

First up was the controller needed 12V to run on, there is almost 12V part of the stock control, but it is only on while the motor is running, so I picked up a small AC to 12V converter, it fit in the case nicely.
I picked up a pretty cheep temperature controller, tried it on the bench and it seemed OK.

I broke the ON/OFF switch while taking things apart, pretty much crumbled. I replaced it with a rotary lamp switch. I will replace this again once I find a better switch. The issue is you just keep turning clockwise for on - off - on - off...... I want a back and forth on/off.

Most of my processing is at 38C so right now as I type this, the bath is heating up to 38C and I will calibrate the controller if needed ( there is a programmable offset ). I will set it up so that the displayed temperature is what I measure in one of the chemical beakers.

Within days of originally buying the CPE I added a circulation pump ( aquarium pump ). It has worked well.

Having things apart gave me a chance to clean out some of the grunge that's hard to get to.

For now, it works. When I get a switch sorted out, there is some clean up to do wiring wise. Will be interesting to see it the temperature holds better.

Quick update, pleased with the way the digital controller is working out. I have done several rolls of film, some at 20C and some at 38C. I did calibrate it to be 1C high which seems to give me the target temperature in the chemical bottles/beakers while the tank is the 1C high. temperature seems stable to 0.5C. The biggest fluctuations come from pulling bottles or beakers. Maybe I can reduce that some by changing the circulation flow in the tank. I really like being able to just set the temperature I want and get it, not have to fuss with getting the knob set just right.

Added one more bit to my CPE.

Now that I found a 6 step E6 kit again, I added a holder to the end of the tank to hold two more beakers. In the past I used to just let 2 8 once bottles float there. This setup is working well.