Arduino interface with MX067

Hi sorry my first post is a plea for help!

I'd like to control a high power PWM motor controller using my arduino. The MX067 has a potentiometer on the board that is used for the purpose of changing the motor speed. It does this by varying the voltage carried on the wiper between 0 and ~7v. Initially I planned to use a digital potentiometer but I have realsied that the wiper voltage cannot exceed the supply voltage of the IC. (which 6.5v max). Anybody got any ideas for what I can use instead?

(I've tried the hook up an analog output and cross fingers solution to no avail :-[)

Simple solution would be to couple a servo to the pot, and drive the servo.

Or change your ESC.

Maybe you could hack the ESC, and feed PWM direct to the output stage.

If you look at the schematic you will see that this pot just controls the voltage on a comparator to generate the PWM signal. However it is in the range of 0 to 12V.

Therefore to use this with an arduino, remove the pot and wire up one of the Arduino's PWM outputs to a transistor, with a 1K base resistor and 4K7 collector resistor. This gives you a 12V PWM. Next take the output at the collector and put it through a low pass filter (R and C) to give you a smoothed DC voltage and apply this to what was the wiper of the pot. See:- http://www.thebox.myzen.co.uk/Tutorial/PWM.html

Thanks Groove and Mike - I'm using a Romeo http://www.yerobot.com/products/manual/RoMeo%20Manual.pdf

Would I be best using one of the motor control outputs or just use a standard one? - I'm guessing the circuit won't have any significant current requirement...

I'd like to learn how to do this - if I go away and do my calcs, will you you cast your wise eye over them? Will be later on though - got to go Christmas shopping....

How about I use one of the 2A PWM outputs on the board avoiding having to add a transistor. Then make a low pass filter with a 6.8k resistor and 0.47uF cap? does that sound ok? I intend to change the speed of the motor at most 10 times a second (it's going to gradually ramp the speed up over about 1 second. Sorry if that's utter guff - I'm really not an analog guy!

Should be able to pick up the bits for this later. Will post my results :)

Have only been able to test with a test load on the ESC so far but it works :)

I went for the transistor approach from a PWM pin in the end. I breadboarded it this morning and knocked it up stripboard just now. If anyone would like it - I'll draw a schematic.

Thanks Mike!