Build the Animatronic Hand

Make the Hand

  • Align a piece of cardboard so that the "grain" of the corrugated flutes is oriented vertically
  • Use a pencil to trace your hand
  • With a hobby knife, cut out the pattern of your hand

Hinge the Joints

  • With a pencil, mark the locations of each finger joint
  • Gently score each mark with your knife to aid in bending
  • Carefully bend each joint to give the fingers a natural curl and to guide them later when they're pulled with a cord by the servos

Add Straw Channels

  • Cut small segments of drinking straws to length so that they will fit on each finger segments without colliding with their neighboring segments when bent
  • Using the hot melt glue gun, secure each segment in place

Add Cords

  • Cut four lengths of cord, string, or yarn to about 18" each
  • Thread each cord through the straw of its respective finger
  • Fold the tip over and glue it in place from the back
  • Once the glue has cooled sufficiently, test the pull of each string -- they should easily curl each finger

Rubber Band Return Tendons

  • Cut each rubber band into a single strip
  • Glue one end of each band to a finger tip on the back side of the finger
  • Using a pencil, poke a hole through the back of the hand at the base of each finger
  • Push the rubber band end through the hole, then pull it taut enough to give the finger a good return action, but not so tight that it can't be bent by pulling the cord
  • Tie off each band in the palm area

Mount the Hand

  • Position the hand at one edge of the box
  • Mark two spots to poke holes in the hand and the box side
  • Poke the holes through with the Make Do tool
  • Screw in two screws to hold the hand in place

Mount the Servo Motors

  • Lay out the servos so there will be enough clearance that the servo horns don't collide
  • Mark positions for each servo -- keep the marks a bit smaller than the dimensions of the servo so the fit will be tight and hold them in place
  • Cut the holes out with the hobby knife
  • Feed the wires into the box, then press the servos in place

 

Thread the Cords

  • Orient the shafts fully counter-clockwise
  • Lift of the servo horns and then reposition them on the shafts so the arm you'll connect to the cord is at the one o'clock position
  • Thread a cord through the end hole on that arm for each servo
  • Pull the cord taut, but not to much -- there should be a slight bend to each finger
  • Wrap off the cords around the servo horns like you would a cleat hitch -- a figure eight pattern where the final loop wraps the tail underneath the cord so it doesn't come loose

Run wires to CRICKIT

  • Position the CRICKIT on the box so there will be enough clearance to use the capacitive touch pads
  • Mark a position on the box near the servo connectors to run the wiring
  • Cut out the hole, then pull the wires up through
  • Plug in the servos -- the yellow signal wires should be at the outer edge of the board
This guide was first published on May 23, 2018. It was last updated on May 23, 2018. This page (Build the Animatronic Hand) was last updated on Nov 17, 2019.