Analog digital clock

What can you do with six vintage ammeters ? Make a clock of course! An analog digital clock! I had six very nice ammeters that were probably made in the 1950s in Sydney, Australia. The marked scales were not ideal: three of them are marked 0 to 1 in 0.2 increments so they can be used for the Y digit (0-9) in a time code with format XY:XY:XY; but the other three are marked 0 - 500 mA/0 - 15 V so the 0-500 mA range sorta works for the X digit (0-5). I could have bought meters that were easier to read but that wasn't in the spirit of the project.

I needed a small computer to drive the meters that could be easily networked and run NTP. Because I am using Beaglebone Blacks at work, I decided to use one of them. That meant 6 DACs so I found a dual DAC that was easy to use because it had a built in amplifier, allowing the DAC to directly drive the ammeter. I decided to prototype the circuit (right) before I made a PCB and it was just as well, because I had misunderstood a few things in the data sheets.

prototype of the analog digital clock Prototype
closeup of the finished clock

I haven't made a PCB in a very long time and eventually decided to use the free version of Eagle for my PCB design work. Eagle also had the advantage of a Linux version being available. Update: KiCad is what I use now.

Software for driving the clock is available from github.

It's been ticking away since 2016.

Here's a video (1 MB):