[Brett] has had Nixie tubes on the brain ever since being introduced to them by a good friend of his. He decided that building a Nixie-based key chain would be the best way to familiarize himself with the technology, while also giving him a project to enter in the 555 Design Contest. He dug up the smallest Nixie tube he could find that displayed digits, and got down to business.
The biggest obstacle he ran into was figuring out how he would provide the high voltage required to light the Nixie tube. He eventually built a transformer circuit driven by a 555 timer, using a small 12v battery as his power source. Once everything was up and running on a breadboard, he designed and etched some PCBs, then soldered everything together.
The end result is a nifty little key chain that flashes the number 5 when a button is pressed – pretty appropriate for the 555 contest. It’s a great looking project, though we’re still not 100% sure what we think about a naked high voltage circuit residing in our pocket.
Keep reading for a pair of videos documenting the key chain’s construction and operation.