Analog digital clock
What can you do with six vintage ammeters ? prototype of the analog digital clockMake a clock of course ! An analog digital clock. I had six very nice ammeters that were probably made in the 1950s. 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 to 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 really in the spirit of the project.
 
Because I am using Beaglebone Blacks at work, I decided to use one of them to drive the ammeters. 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.
 
I haven't made a PCB in a very long time so I had a bit of a look around for suitable software and eventually decided on the free version of Eagle. This also had the advantage of a Linux version being available., which suited me because this is my preferred environment.
 
 
Software for driving the clock is available from github 
 
To be continued ...

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