Robot Arm

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The robot arm was purchased with the intent of being used to create a mechanical turk. The code going towards this goal lives in ~ssalbiz/arm, use "git clone ~ssalbiz/arm" to make a copy.


The arm is a Lynxmotion AL5D.


Currently the arm is controlled by interfacing directly with /dev/ttySx or /dev/ttyUSBx . The syntax for controlling this is by sending the following string to the board:

#<servo id> P<position> S<speed> T<time>

You can control multiple servos with one command

#<servo id> P<position> S<speed> #<servo id> P<position> S<speed> T<time>

S and T are optional parameters


  • <servo id> - id of the servo being controlled (includes jaw)
  • <position> - servo rotation position, generally between (500,2500)
  • <speed> - speed of rotation; 100 means 10s to rorate 90°; leaving this off generates fast movement, 400 seems like a "safe" value?

if both speed(s) and time are specified, time is a "minimum" and speed is a "maximum", i.e. the motion will take at minimum T milliseconds, but servoA will move no faster than speed SA

Servo key and degree of motion

  • 0 - Base
  • 1 - Shoulder
  • 2 - Elbow
  • 3 - Wrist
  • 4 - Grip
  • 5 - Wrist Rotate


The current purpose of the robot arm is to make an entity that can play chess against a human.


Not being worked on. Need to complete the following:

  • Complete physical modifications to robot arm to allow it to reach all pieces on the board
  • Calibrate arm base mount against chess board squares
  • Make the robot arm code talk to a chess program
  • Make the chess program talk to the chess vision code
  • Make the arm not have terrible things happen when the servos heat up

External Links