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Topic: [closed] Reverse Engineer Motor circuit (Read 337 times) previous topic - next topic


Aug 26, 2018, 11:15 pm Last Edit: Aug 27, 2018, 10:46 pm by 3dprinter
The picture shows the circuit and the hardware from the manual. This is a vending machine, each motor will dispense one unit of whatever by rotating a helix for half a turn, appropiate geared down from the motor. "Clearly" the microswitch and the orange wheel it touches do "something" so the control circuitry knows the half turn has been done. The system only turns one motor at a time.

I want to replace the system controller with an Arduino (plus required driving circuitry) but am wondering how the system stops at the notch and/or how it gets out of the notch-position.

Concentrating on one motor, say the topmost, it is "obvious" that applying + on pin 2 and GND on pin 1 wil make the motor rotate. If the switch goes "open" at the notch, then yes, it will stpo, but nothing will make it carry on again. The diagram seems to show that in both switch position there is "on". The travel time of the microswitch is unlikely to be enough for the motor to stop.

So how do you think this works? I do not have a scope or other measuring, only a multimeter, and it will not react fast enough.

An additional challenge is that on the tiny circuit board there are two diodes and a resistor, not a capacitor. (It is just visible on the manual page picture. I have looked at in RealLife, and unless the capacitor is hiding on the underside of the board, there is a resistor instead(?)/additionally(?) the capacitor)  The 50 odd motors are wired in a matrix, so one of the diodes might be there for the matrix to work.


I think the motor circuit is interrupted for a short length of time and whatever was controlling it was watching for that interruption. How do you think it operated? Surely you have a better clue than I have.



No, not really, Paul, otherwise I'd have written it.

Meanwhile, I've been able to play with it, and applying a nice 12V directly will turn the motor, and it does not matter what the switch does. The end user has decided that is good enough, they do not need an exact half/full turn.

So thread closed.

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