Endex DCMD57 Treadmill Motor Controller

I have a motor, belt, and main control board from an old treadmill that I want to use to power my grain mill. I long ago lost the UI panel, and struggled to find the details. I've done some digging, and in order to save others the hassle, thought I'd leave a note here.

After a fair bit of searching and head scratching, I finally found a pair of fairly old All About Circuits discussions: https://forum.allaboutcircuits.com/threads/test-board-for-treadmill-dcmdx.100834/ and https://forum.allaboutcircuits.com/threads/test-board-for-treadmill-dcmdx-2.184554/. These pointed me to the answer in a spanish-language youtube video - diagram at 26:12.

For your convenience, I present the wiring diagram for the 7 pin connector at the bottom edge of the board (if the FETs are at the top).

Basically, Pin 1 puts out 12ish volts, which would have been sent to the stock UI. The MCU on the main board expects 5v, which was delivered via this connector, not found natively on the driver board. Therefore, to spoof the original UI we need to provide 5v. We can add a LM7805, taking its input voltage from pin 1, GND from pin 2, an sending the 5v to power the MCU to pin 6. Connecting pin 5 to ground enables the motor. Temporarily shorting pins 3 and 4 to ground increments or decrements the speed (respectively).

If you just need to get the motor running, this should be enough.

For a grain mill, I want to turn the motor on or off, and not futz around with speed control. I want to set it at around 240rpm at the rollers, and leave it there for ever. Having to flick a switch to enable the motor, then repeatedly press the + button until speed is right is not ideal. My first idea, which I may still use, is just to use an arduino to send the appropriate button presses. i.e. if I determine 10 presses of the + button gets me to the right speed, when I power up the unit, the arduino would enable the motor, and then send 10 button presses to the board. Pins 3, 4 and 5 appear to be pulled high to 5v - they measure 5v, and shorting them to 5v has no effect - as such, no hardware beyond the arduino and any input hardware would be required, This is a trivial thing, but lacks elegance.

While searching for the wiring info however, I also found this video by FoulkesBrau and it gave me some ideas. I haven't yet tested them:

At around the 6 minute mark, Craig identifies chip U3 as an A3020v optocoupled IGBT, which appears to be the bridge between the 5v and mains voltage circuits, and what ultimately transmits the PWM signal from the MCU to the motor.

My thinking here is that one could bypass the board's MCU and provide their own, outputting whatever PWM signal was desired. For my own use, I would have a PWM signal varied by a pot so that I could adjust the speed easily, but rely on it being consistent each time I power up.

That said, I'm not sure what soft-start code etc. may be present on the stock controller, so I may not even try this. I could just use a pot to tell my arduino how many button presses are required...

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Endex DCMD57 DCMD67 treadmill motor controller