This first project is a set of artificial pumpkins, carved as a Pac-man, three dots, and a ghost from the classic Pac-Man arcade game. Sitting behind it is a motion-activated sound effects unit.
A Passive Infrared Sensor (from Radio Shack) is used to detect when someone walks by. The output signal is 3V, so I used 5V into a transistor triggered by the sensor output to provide the 5 volts needed to trip the relay. I used a 9V 20 second digital recorder from Radio Shack for the sounds. I downloaded Pac-man sound effects off of the Internet and just recorded them using the built in microphone. I removed the playback button, and soldered the relay leads to where the button mounted. Then I put it all in a project box.
The only drawback is that the sound isn't very loud. It would be easy to snip off the speaker from the digital sound unit and run the output either through an amplifier or to a powered speaker.
This was a quick build, using an R/C car concealed underneath. The body is built out of foamcore, with a styrofoam head and bumps. the antennae are just two straws, and there are two LEDs as eyes. The battery pack for the eyes is also concealed underneath. It's not very realistic, but that way the trick or treaters love it, without it being too scared when it suddenly starts moving and chases them.
This was carved on a faux pumpkin (from Michaels). It is based on a great pattern by Noel (www.fantasypumpkins.com), but much simplified to only involve cutting. The original pattern is much better, but involves shading as well as cutting. The original pattern is on Noel's site. The simplified pattern is here.
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