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How to disable a 2 hour timer on a Walgreen 4 mode heating pad Controller model CM 12 and Heating pad model PM12? Answered

I have the model noted above. The IC is a Sonix SN8P2602CSG. Other notations on the IC are "195KNKZ03" and "BV05". See enclosed photos of inside of controller. I want to use the heating pad as a fermentation heater.


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11 months ago

Thanks for the information. I can control the heating with an external sensor and thermostat. It appears that one of the wires coming from the heating pad is a sensor that feeds information back to the controller, as I see when I attach a kilowatt meter on the heating pad the watts appear to range from 1 to 60. The heating pad does cycle when it is at temperature with varying amounts of watts. I will see which of the 3 wires from the pad is the sensor wire and just use an external sensor and thermostat such as a Poniie 10 amp aquarium thermostat control.

Jack A Lopez
Jack A Lopez

11 months ago

I think what you are looking at here, is two heating elements (on pins H1, H2, H3), turned on and off via two TRIACs.

I am guessing the trigger signals to those TRIACs come from the microcontroller.

That is the big 18 pin IC, the Sonix SN8P2602C. It is an 8-bit, general purpose, microcontroller (MCU).

I think this page, is sort of the page for the particular family it is in, and there is a data sheet for it linked on that page too.


The bad news is, you cannot just disable this "2 hour timer" because the mechanism that does that is code. It is a program, running on the MCU, and there is not an easy way to get into that microscopic place, and change things around... even if you could comprehend exactly what needed changing.

The good news is, this board has lots of other useful stuff.

It has a crude DC supply, maybe 5 volts, for powering the MCU. Actually I can see parts of that, including the zener diode ZD1, and the big electrolytic cap C2.

There is probably a zero crossing detector of some kind, to tell the microcontroller what "time" it is, with respect to the mains AC waveform, so it can know when to send the trigger signals to the TRIACs.

Anyway, if you can figure out exactly what the strategy is for driving those TRIACs, I suppose you install your own microcontroller, and program it to do what you want it to do.

Or if you are not so good at programing microcontrollers, you could just throw this circuit board into your junk box.

Then connect those heating elements to a lamp dimmer, and then you know, like, turn a knob to throw some power at them.

Although that is not closed loop control, I think it would be a good way to get started.

If you want closed loop control, like a temperature sensor, and a controller to turn the heating elements on and off, in response to the signal from the temperature sensor, for to keep the temperature constant, or ramp it up and down, or whatever... well, I guess you will have to figure out some way to do that.