A numitron is a seven-segment display using lightbulb filaments in a single glass envelope. These displays actually use seven grain-of-wheat lightbulbs per digit. They were made for aircraft instrumentation. My friend John had a box full of them from when he worked for BAE Systems. I'm using constant-current LED drivers to limit inrush current, and pulse-width modulate the segments for brightness control. I'm not multiplexing the display, so each segment has its own driver. The case is metal, so I had to use an external antenna for the GPS unit.
I wanted the clock to look like something you'd find on a lab bench in the 1980's. I found a nice instrument case and had my friend Mark machine the front panel. He used water-transfer decals for the legends, protected with a layer of clear-coat spray paint.
