It's the most wonderful time of year. The air is crisp, yards are decorated with lights and inflatable figures, fir trees are on sale at the hardware stores, television commercials are laced with holiday cheer and jingle bells -- that's right, it's Halloween.
Last year for Halloween I decided to create an Arduino-based electronic scare device to creep out our trick or treaters. (An Arduino is a low-cost microcontroller that is easily programmable to do all kinds of cool stuff. Check out this post where describe how I used one to make a cool hat for my LARP).
I knew we were going to be sitting out front of the house (next to our creepy red tree), so I wanted something that I could rig up to or near our candy bowl. After going through many overly-complicated ideas, I narrowed it down to a button-activated screaming pumpkin. Here's how I made it:
Step 1: Carve some pumpkins.
Step 2: Set your jack-o-lanterns outside to get some "natural weathering" from the #$%@ chipmunks.
Step 3: Wire up the electronics. I used an mp3 shield and NeoPixel ring from SparkFun, which were both in my spare parts (aka abandoned projects) bin. Shields are specially designed circuit boards which are the same footprint as your Arduino -- that way, instead of getting specialty chips and wiring them up by hand, you just stack them on top of your Arduino. In the case of the mp3 shield, it's literally plug and play.
NeoPixels are programmable LED lights where you can change color and intensity of each light using a few program commands. The reason I used NeoPixels instead of a standard boring old red or yellow LED is because that's what I had lying around. As a bonus, I was able to program them to have a very realistic flame effect using random tones of, well, red and yellow.
I should pause here to say a word about soldering safety: soldering irons get very hot, and can easily start a fire if improperly handled. It's important that you get one that has a clear indication as to when it's turned on. Oooooor you can get a really cheap one no safety features and improvise your own.
Step 4: Prepare to scare the kiddos!
In the picture of our jack-o-lanterns above, one had my programmed artificial flame and one had a real candle in it. The colors didn't quite match (though they looked a lot closer in real life than they did on my camera), but you couldn't tell by looking which one was real and which one was the fake. Go ahead and make a guess. Then push the button IF YOU DARE!