This Halloween a friend sent me this instructable and wanted me to modify the design and recreate it. I built a system that uses infrared sensors and infrared LEDs to detect when a hand is in the candy bowl, and use an Arduino to command a power switch tail which makes a solenoid trigger a can of silly string. To make connection of all the wires easy, I glued a terminal block onto a project enclosure and soldered short jumper wires to connect it to the Arduino. The Arduino was powered by a 9V battery and the solenoid and powerswitch tail were powered by wall AC power.
Also please vote for this project in the Halloween, Pumpkin, and Microcontroller contest!
Step 1: Software
Attached to this page is the Arduino code for this project. The IR Led is on pin 3, the IR sensor is on pin 4, and the powerswitch tail is on pin 12.
Step 2: The Build
I started off the build by soldering wires and resistors to the IR LED and sensor. They were also glued onto a plastic pumpkin. Next I mounted a solenoid and silly string can to a few pieces of foamcore. I then cut a hole for the terminal block and glued it in place. After that was done, I soldered header wires to the terminal block and connected the header wires to the Arduino. Finally I placed everything where I wanted it outside, and this project was ready to go.