I’m a little late on this one, but better late than never. The winners in the Make/Design News Gadget Freak contest have been announced. If you recall, the contest was sponsored by TI, Allied, and Alibre. Grand prize was $1000 and a storefront at Maker’s Market, free for 6 months.
Second prize was $500, and there were two third prizes awarded, a $100 gift certificate to the Maker’s Market.
The photo shows the entry from the grand prize winner, Rick Prescott, who used an array of thermopile sensors to build a heat seeking sentinel for a Nerf foam-dart shooting machine gun. The sensor array, along with an ATMega controller, scans the area looking for new heat signatures that stand out from the background. When detected, the ATMega points the gun in the direction of the heat source and fires. The gun offers both a single shot mode and a full auto mode, where the gun fires continuously as long as the lock is maintained.
Minor modifications are made to the gun to bypass the trigger and put it under microcontroller control, and more significant mechanical modifications are made to the tripod to stiffen it up, remove the tilt, and add computerized pan. Rick paid good attention to detail, modifying the plastic cases to incorporate epoxied in connectors, housing the electronics in a project box with well placed switches and indicators, and providing CAD files for the sheet metal pieces he had to fabricate.
Prior to reading about this project I had never heard of a thermopile sensor. They use the thermoelectric effect, same as a thermocouple, to detect heat. This project uses a TPA81, which is 8 thermopiles arranged in a row, with suitable shrouding and lenses so that each sensor has a field of view of about 6×6 degrees, giving a total field of view of about 40×6 degrees. This single dimensional array of sensors is why the gun only has pan, no tilt. The detector array uses an I2C bus to communicate with a microcontroller.
One obvious change would be to mount the gun on a two axis gimbal with both pan and tilt motors, and add additional thermopiles to form a 2D detection array. At about $100 each, the additional thermopiles would start adding up costwise pretty quickly.
Congratulations to Rick for winning the Gadget Freak contest, and hopefully he’ll get a good return on his investment from the Maker’s Market storefront.
Design News Gadgeteer