We started with a Vistaquest VQ1005. It's a very cheap, small, light, 1.3 megapixel camera that is easy to take apart and hack. It also has a SD card expansion slot and can function as a webcam. BTW, you can see our LauchPad MSP430 uC hack of this same model camera here.
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Time to void the warranty. The Vistaquest VQ1005 comes apart easily with four small screws. We found a node on the circuit board that triggered the camera to take a picture when connect to the "-" lead of the battery; GROUND. We soldered a "trigger wire" from a 555 Timer to this node.
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We then needed a way to connect the trigger wire to GROUND automatically. We used a 555 timer chip to provide this function. A low power CMOS 555 can be purchased for about one dollar. If the Vistaquest VQ1005 does not take a picture in 60 seconds it will shut off, so we designed a RC network for the 555 timer that would trigger a picture about every 20 seconds. The circuit looked like this:
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Then we breadboarded a prototype.
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After cleaning up the prototype, the rig was cleaner, smaller, lighter.
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Here is the finished rig protected and ready for some kite crashing.
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Here are a few vids taken with the setup: