Animatronic Hand

by John Park

published May 23, 2018, last edited January 21, 2025

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Beginner

Project guide

Build the Animatronic 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

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

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

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

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

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

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

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