The Idea
I wanted a way to scare people when they are taking candy from a candy bowl. It then hit me, that I could use a spider, to drop down from the overhead light, and make noise, scaring the soul out of the people taking candy.
How It Works
An ultrasonic sensor on the light fixture above the bowl, would detect people walking up the steps (by constantly checking the distance). When the distance went below a certian number, the Arduino sent a signal to a motor connected to the spider. The signal told the motor to drop rapidly to roughly the height of the bowl. The Arduino also sent signals to an MP3 player, which played a scary sound loaded on an SD card. The MP3 connected to an AMP, which amplified the sound before sending it to the speakers also mounted on the light fixture. The result of this was, when someone is walking up to take candy, a spider drops, and scary noises play. Then the spider is reeled back up waiting for the next person.
I tested everything before setting everything up on the light. Once I ensured that everything worked, I started mounting everything. The ultrasonic was placed at the front of the light fixture, pointing to a position where people would walk. I wired that to the back of the light fixture where all the components were (Arduino, MP3, AMP). Then I placed the motor. This was the tricky part, as I couldn't fully get the motor to fit, but eventually, I made it work. With the spider, and ultrasonic sensor connected to the Arduino, I did a quick test; did the spider drop. To my suprise, it worked! After I knew that the spider dropped, I started working on the scary noises. I mounted the AMP, and MP3 player next to the Arduino, and wired everything up. I connected the MP3 to the Arduino, and the AMP to the MP3. I then mounted the speakers, and connected them to the AMP.
Finally everything was ready. I started testing. I made some tweaks, and then it was ready.
Demo
On Halloween this was a sucess. It scared people so bad, that they ran away ;)
Here is a video on Halloween of a kid getting spooked by the spider:
Next Steps
What would you build next? What would you do differently?