I’m actually coming to robotics out of left field. I design and build electronics for musical effects pedals, fuzz, echo, etc. What I want to do is have one pedal control the knobs on another. I have an expression pedal shell which is basically a potentiometer controlled by a foot treadle and I want to translate the movement of this to a servor (or something) that turns the knob of a different pedal. The rotation of both should be identical, both potentiometers would turn a little less than 360 degrees and they both have the same size shaft. The two pieces will be wired together and I would like it to be run by 9 volts. I have some experience with RC cars and helicopters so I know servos would work but the sensor and controller for this I need help with. And it should also be as cheap as possible. Any ideas?
Don’t need a sensor because the pot of the expression pedal will do the job. What I need is a way to translate a 100k variable resistor into about 300 degrees of movement on a servo. Running off 9 volts.
Did you ever figure this out? I’m interested in the same thing. I already know how to work with microcontrollers, but know almost nothing about motors and robotics. What I’m after is a way to digitally control analog potentiometers, quickly. Existing motorized pots don’t work for what I’m doing.
You’ll need to provide a product link for what you’re hoping to use.
Hi Wounded Paw, welcome to the RobotShop community.
Potentiometers output a variable voltage which can be read by a microcontroller. The microcontroller can in turn control the position of a servo motor or other actuator.
Assuming that the potentiometer outputs maximum 9V, you could use a voltage divider to bring the 0-9V ouput down to 0-5V (TTL level) required by most microcontrollers. You could then read this voltage and convert it into a numeric value inside the microcontroller. The microcontroller would then command a servo motor to rotate to a position proportional to this numeric value. Most standard hobby servo motors (Hitec, Futaba, GWS) do 180 degrees out of the box. Beyond 180 degrees, there is a higher level of complexity as specialty servo motors are required. Otherwise you could also use DC motors with optical encoders or potentiometer feedback, not to mention stepper motors with limit switches at the start/end points. We encourage you to experiment and find a solution that best suits your needs. Some specialty servo motors that may interest you are the Bioloid and Megarobotics servos which offer 300 degree rotation.
Pedal Potentiometer -> Voltage divider -> Microcontroller -> Servo Motor
Some product suggestions:
Voltage divider: Phidgets Voltage Divider, Product Number : RB-Phi-50
Microcontroller: Arduino Diecimila USB Microcontroller, Product Number : RB-Ard-03(Arduino is excellent for beginners)
You might also want to consider using a normal servo but with a 2:1 gear down, similar to RobotShop’s RB-Lyn-174 (but without the 1:1 ratio).
The pan and tilt gearboxes all increase torque and decrease speed instead of increasing speed (which would mean a standard servo could rotate a shaft 180x2 degrees). Servocity does have mechanical solutions (gears and sprockets) you could probably special order through RobotShop.