How do I control potentiometers using my PC?

Hi,
I am trying to control an RC car using my computer. I have taken apart the controller so that I just have the circuit board and battery pack. The RC car is controlled using two potentiometers which are turned using a trigger for forward/backward and a wheel for left/right.
Each potentiometer is connected to the controllers circuit board differently: one is connected using a 3 pin plug type thing (I believe it's called a molex plug?) and the other is just soldered into the circuit board.

What I want to do is find a way of controlling these potentiometers using my computer, but haven't got a clue how to do this!

Any input at all will be appreciated :slight_smile:

Toby

Think this thread might help you to get started
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1267798049

I don't entirely understand that post, but would I be able to simulate the output of the potentiometer using the arduino?

Thanks

Yep, that's the idea of the post, using PWM you can simulate a 0-5V by varying the duty cycle of a square wave. http://arduino.cc/en/Tutorial/PWM But as it is simulated it will not allways work. The proof is in the pudding test.

To control the PWM you connect the Arduino to the serial port of your PC (there are many posts how to that) and let a PC application send appropiate values to the Arduino. E.g. you could use your mouse X and Y values (+ buttons + scrollwheel) to be send to the Arduino which forwards them by means of PWM to your RC.

Rob

You might be able to put servos on the existing pots, and move them mechanically. Which would be rather wonderfully ironic. :wink:

Depending on the design of the transmitter, it might be possible to inject servo pulses generated by the Arduino directly into the circuit.

Hi,
Thanks for the reply, I like the idea of moving the potentiometers using servos, it seems much more achievable than simulating the potentiometer turning.

My next goal is to work out how to do this using VB.net... I have looked into doing this using Firmata but I don't seem to be able to get it to work. If anyone has any idea how I might go about doing this I would be very grateful!

Thanks again.

If you know the value of the potentiometer and the max voltage they are exposed to you can use something like this
http://datasheets.maxim-ic.com/en/ds/DS3502.pdf

Or you can build a resistor resistor ladder that can be controlled digitally. It's a crude but effective DAC.
http://blog.makezine.com/archive/2008/05/makeit_protodac_shield_fo.html

More advanced would be using the arduino's PWM and a transistor or mosfet and some filtering to create a more flexible DAC.

The DIY DAC that mrmeval mentioned can also be purchased as an R/2R ladder IC.

Something like this: