Made sure I did something constructive today…
Added on to my circuit board from the previous post. This is the heart of any clock: the crystal oscillator. I’ve explained it more or less in previous posts, a 4.194304MHz quartz crystal is set oscillating while a CD4521 24-stage frequency divider divides the frequency in to discrete steps by powers of 2. Of course the primary use for this is to get a clean 1Hz output from the thing.
After smacking my forehead and soldering one joint I forgot about when the initial test didn’t work. I’m happy to report it is working just fine. Here’s some pics and a video of the scope readout on my crappy (but working) PM-3200:
I think I had it set on 2 volts per division and there’s some parallax error from my crappy camera skills but there you have it. You can see that half at least of the board is still unpopulated and this will house the two seconds counters which will take the output of the 1Hz (i.e. one pulse per second) and convert that into counting minutes. Unfortunately, I highly doubt I will be able to fit the minutes and hours counters on the board (though it might be fun trying, $10 says I burn myself) so they will live on a board which I will mount on top. Beyond this, it is going to be a very boring wiring maze.
I have yet to find a suitable box for it, time to raid antique and junk stores methinks… if only I could work with wood (and make it look good) I would build my own, but alas, I stink at carpentry.