Hacked Gadgets Forum

May 30, 2007

Robot Arm using Potentiometers and Servos

at 4:31 am. Filed under Cool Gadgets, Electronic Hacks


This robot arm uses potentiometers to determine where the human arm is and then a servo controls the robot arm to match the position.

“Each joint on the master arm is a potentiometer(a variable resistor). A joystick port basically checks the resistance. By itself, this resistance means nothing, so I wrote a little routine that converts a resistance into an angle that the servos can understand.

To do this on the elbow for example, I straightened the master arm, and checked the resistance. Then I tried sending various numbers to the elbow servo until I figured out what number meant straight. I did the same for fully bent.

With these 4 numbers in hand I was able to write an equation that maps any angle on the master arm to a similar servo angle on the slave arm. I also used these numbers as hard limits on the values I sent to the slave arm.”


Generic effective for treatment premature in ingredient priligy . Priligy is tablet hours sex extend time can before is...

Related Posts

Altoids Robot
G-Dog Servo Robot Dog by G-Robots
MechRC Robot now available at Trossen Robotics
Drumming Robot
555 Timer based Servo Tester
Gir Robot Build
RobaNova-1. Good Hacking Platform?
Dancing Robot



10 Responses to “Robot Arm using Potentiometers and Servos”

  1. Robot Arm using Potentiometers and Servos | Technology Blog Says:

    […] Original post by http://hackedgadgets.com/2007/05/30/robot-arm-using-potentiometers-and-servos/ […]

  2. NGinuity Says:

    This is how most of the manual rotor systems for directional antennas work…kind of cool actually.

  3. joebob Says:

    still has some bugs to work out. but other than that, good job!

  4. listofoptions Says:

    wouldn’t an analouge version with a comparitor work better, it could be less jumpy….

  5. Alan Parekh Says:

    Hi listofoptions,

    Sure an analogue version would work well, that is actually how the antenna pointers that NGinuity mentioned work. I guess the creator wanted to use a microcontroller. There are also lots of benefits using a controller like speed limiting and position restriction.

  6. Reinaldo Yañez Says:

    Hi. You could try to use the following idea “to be less jumpy” 🙂

    CalculatedSensorPosition = 0.9 * OldValue + 0.1 * ActualSensorPosition

    CalculatedSensorPosition – is the calculated value of the potentiometer
    OldValue – is the last calculated value of the same potentiometer
    ActualSensorPosition – is the actual reading from the potentiometer.

    (use CalculatedSensorPosition in your formula, instead of
    Convex combination coefficients (0.9 and 0.1) can be adjusted.
    This is a rather crude “digital filter”.
    Best Regards,

  7. John Fenley Says:

    This project was tons of fun, and I learned a lot.

    One benefit of the control system I used is remote operation. Its difficult to tell, but in this video the arm is powered by a battery and control signals are being sent wirelessly from a transmitter (out of view to the left).

    I like the “digital filter”. I used a similar method on a later project. It worked great.

  8. Alan Parekh Says:

    Hey John,

    Thanks for stopping by and clarifying the operation.

  9. zedomax.com Says:

    Robot Arm using Potentiometers and Servos

    Download latest version of Flash to view video! . Click Here to View in Full Screen Mode
    Wow, this is sweet… This could easily be implemented for medical robotic arms.
    A master/slave system I built using potentiometers, servos, and an IFI roboti…

  10. lifekludger » Robot arm makes my brain ping Says:

    […] [via hacked gadgets] […]

Internal Links:



Hacked Gadgets

Site Sponsors:

Nuts and Volts Electronic Labs Trossen Robotics Free Technical Publications Blue LED


Recent Comments:

More RSS Feed Options

Site Sponsors:


Interesting Sites: