Hackaday forum member [nes] was training for an endurance race, and rather than having someone verbally call out his lap times, he wanted something he could keep in-vehicle to help keep track of his performance. With the race budget running dry, he and his teammates needed something cheap, if not free, to get the job done.

He scored a “broken” GPS receiver on eBay for a measly £4 and found that the receiver worked, but corrupted software prevented the unit from mapping routes. Since he didn’t require routing functions to keep track of his lap times, he splayed the GPS receiver open and started hunting around for a serial bit stream. He found what he was looking for after a bit of probing and hooked it up to his computer to see if the data contained NMEA sentences.

He cut the receiver down to the necessary parts and then started work on the lap timer itself. The timer uses an ATMega32 to run the show, displaying relevant time and location information on an LCD panel he scavenged from the trash bin.

He admits that the wiring is a bit questionable, but says that after about seven hours of rough use, everything is still intact and working great.