[Windell] of Evil Mad Scientist Laboratories took an ancient Nixie tube based frequency counter and converted it into a clock. The unit he got his hands on is an HP model that was still in great shape. He’s using an internally generated one second pulse as the clock signal, but some modifications are necessary to display time. That’s because the frequency counter is base 10 and clocks use a quirky combination of base 60 and base 12.
It wasn’t too much of a problem to rig up a system to track minutes and seconds. The tens digit for each is monitored by a couple of AND gates that he added to the mix. When they detect a ‘6’ the digit is reset and a pulse increments the next digit as the carry. This is more difficult to accomplish with the hours though. Minutes and seconds count from 0 to 59 but hours don’t start at 0. Instead of over-complicating the logic [Windell] used a bit of slight-of-hand. The Nixie tubes for the hours have been rewired so that when the counter is at 0, the filament in the shape of a 1 lights up. No difference in logic, just a translation that makes them display one digit higher than the actual count.
This LED matrix is arranged in a 24×6 pattern for message scrolling. There’s no etched boards here, making us wonder where [Syst3mX] found protoboard this long. He’s using an Arduino to drive the demonstration (clip after the break) but you can use any microcontroller with this setup. That’s because he’s using three shift registers for column data and a decade counter for row scanning, requiring just five control pins.
While you’re going to the trouble of ordering components, maybe you should try your hand at building a touch sensitive LED matrix too.
Continue reading “LED matrix with a gross of pixels”
This clock requires no microcontroller. It’s actually a digital logic counter that functions as a timepiece. [BlackCow] used six decade counters to track seconds, minutes, and hours. The output is displayed on four 7-segment digits using BCD-7-segment decoders that you can learn about in our binary encoded decimal post. The actual timekeeping is done by a quartz clock circuit he pulled from a Mickey Mouse clock. This would be a perfect circuit to build in a digital logic simulator, just follow the schematic and learn as you go.