Motion Tracking Skull

With Halloween fast approaching everyone is jumping on the making bandwagon. Whether it is costumes and decorations or even props, everyone gets into the spirit of things. Halloween is still very much a ‘new’ thing for Australia but it is slowly growing every year with more and more people accepting it. One thing that you will notice now is lots of cheap one dollar stores are stocking up on plastic skulls. These plastic skulls generally don’t do much other than sit there and look scary, but with the help of an Arduino, you can give some ‘life’ to these ‘dead’ skulls. (Puns definitely intended)


Instructables user DIYHacksAndHowTos (Jason) has created a system that allows these simple cheap skulls to look at and follow unsuspecting victims that walk past. Using a series of photo-resistors (also known as light dependant resistors) an Arduino is able to detect the shadow of a person walking by.

Having a Photo-resistor in a voltage divider setup means that with the changing resistance of the photo-resistor, as a result of changing ambient light, there is a change in the value of voltage outputted through the middle wire. You can read the voltage of the middle wire by simply hooking it up to the Arduino’s Analog pin and performing an analogRead.

Having lots of them set up in a line formation means that the Arduino can tell where this shadow is. As a person walks past the skull the shadow of that person means less light on the photo-resistor. The Arduino performs some quick calculations to see which photo-resistor can ‘see’ the least amount of light. The skull is then rotated into position using a hobby servo which is hot glued to the bottom of the skull.

If you would like to make one of your own be sure to pick up the following components in-store:

Then check out the Instructable here.