Published on April 23, 2014
Thinking of a special geeky present to give your teacher on the first day of class? Give them this fully automated eraser, to make erasing even easier. Simply make contact with the black or whiteboard and the eraser will do the rest.
Build the circuit: power + wire + pressure sensor + vibration motor.
Prepare the plastic foam. Here we used a polyurethane foam, but any regular plastic foam works. It is best if the foam is a bit thicker than an inch. Use the interior of your empty tape roll to trace a circle on the foam and cut it out with a utility knife. Make two of those.
Don't have access to polyurethane foam? Try using a styrofoam ball instead! Cut it in half and use it the exact same way.
Take one of your foam circles and dig a small dimple on the upper surface. This is where the puck of your vibration motor will sit. It should be a tight fit. If not, use tape to hold it in place
Using your utility knife, cut a slit through the same piece of foam. Be careful not to cut the wire on the vibration motor! This cut should go all the way through the thickness of the foam, and should be positioned slightly off center.
Thread the pressure sensor through the slit you just made, from upper surface to bottom surface (so it's opposite the vibration motor). Tape the pressure sensing pad down to the bottom of the foam circle.
Use the interior of your empty tape roll to trace a circle onto a piece of felt. Use scissors to cut out the circle, but make it a1/2 inch bigger than the marking. Place the felt on the bottom of the foam, covering the pressure sensor. Secure it in place with tape.
Push your foam circle into the empty tape ring. The felt side should be facing outwards. Press the other piece of foam in from the other side. You will sandwich the pressure sensor, the vibration motor, and part of the wire in between the two pieces of foam.
Put the power Bit and the battery on top or inside the empty tape roll. We used glue dots to hold the bits in place.
Draw an ugly face on the white board and test the eraser on it. When your press down, it will vibrate, helping you to erase more efficiently.