A Nixie tube speedometer for a vintage pickup truck – seems like the coolest combination ever, right? Check out the video above and you’ll see what I mean. For those who have never heard of a Nixie tube, it’s basically a numeric-display (there are also character-display variants) vacuum tube that works very similarly to a neon sign. These things are actually a pretty cool starting point for your own projects (I think Nixie tubes look totally steampunk) and can be found on eBay starting at around ten bucks.
Anyway, Luke Miller over at FPGA Expert recently bought a vintage pickup truck and wanted to trick it out a bit with some custom electronics. He decided to use GPS to measure speed rather than hooking the speedometer directly up to the truck’s sensors, this way the project could be replicated on any make/ model of vehicle. Luke is using a Pmod GPS receiver which he is then running through his Basys2 Spartan-3E FPGA board to make this thing work. The official name of Luke’s project is GPS Driven, FPGA Decoded Nixie Tube Speedometer. That’s kind of a mouthful, so we’ll just call it awesome. He’s got all the design documentation up over at his site, if this seems like something you’d be into.
[The] GPS module sends its data stream via USART that can be captured and decoded. The only thing is needed is speed data. Via trial and error, the data was decoded (seems that documentation of GPS receivers is scarce). A simple look-up table helped to convert kph in to mph. Since [the] truck doesn’t exceed 99mph there are only two Nixie tubes used.