Is it possible to remove the knob on the unit and wire it up to the Arduino to control with code? In my imagination, I was thinking of simply unsoldering the knob, and running wires to the Arduino, perhaps via a breadboard.
If this is possible, is there a particular way to go about it? (I haven't got a strong electronics background, but I can follow diagrams or instructions!)
Obviously you make another machine controlled by the Arduino that just turns the knob but that sounds like a lot of work and expense.
Another option would be to replace the potentiometer on the board with a digital potentiometer which can be controlled by the Arduino - but then you wouldn't have the knob for manual use, though you could connect a knob to the Arduino for manual control through it.
Another option would be to use a different motor control board and use the PWM facility within the Ardunio to control things. However it's not so easy (or cheap) to get high amperage motor control boards for the Arduino.
If you only need control in one direction you could consider the sort of electronic speed control (ESC) used in model aircraft. They are controlled as if they were mechanical servos and can be easily controlled with an Arduino. Look on the Hobby King website.
I think if I was in your situation I would consider a digital potentiometer.
It looks to me that the speed controller you have is designed for an external analog input to control the PWM. Is there any documentation with the controller that describes the function of the 3-pin connector? The centre terminal of that connector is connected to the pot wiper. So my guess is that you can unsolder the pot and provide an analog input instead. It's probably either 0-5V or 0-10V.
If you trace the wiring to the two ends of the pot, then we should be able to tell for sure. I would expect one end to be connected to ground, and the other to +5V or some other fixed positive voltage.
The board probably has something like a pot controlled 555 chip to generate the PWM to a MOSFET. I'd try to input the arduino PWM to the MOSFET at the same point as the PWM chip on the board.
dc42:
It looks to me that the speed controller you have is designed for an external analog input to control the PWM. Is there any documentation with the controller that describes the function of the 3-pin connector?
I asked the seller but they don't have any documentation. I did find this however:
OK, it sounds like the 3-pin connector is so that you can use a pot on a length of wire instead, not for an external PWM input. In which case, the PWM is probably driven being generated from a chip that is running from the 12V supply. I can see one IC on the board in the photo. What markings does it have? are there any other ICs on the board?
In that case, I think you are better off not using that board. If you only want to drive the motor in one direction, then all you need is a logic-level mosfet with low Rds(on), a couple of resistors, flyback diode, a large decopling capacitor. Like this:
but add a 1000uF capacitor from Vdd to ground and leave out ZD1. R1 should be 100 ohms, R2 is not critical but should be 10K or higher. The flyback diode should preferably be rated to take at least the stall current of the motor, but will only conduct that current for very short periods, so it shouldn't need a heatsink. Where it says TTL, that is the Arduino PWM output pin.