June 2025: How to quickly and efficiently set fire to your desk
VCO PCB
And its all done!
It's definitely the most complicated design I've done up to now. The board is probably bigger than it needs to be but overall I'm happy with the PCB layout, despite some odd issues with ground connections[[1]].
I'll write a longer post about how the circuit works once the boards arrive and I find out all the things I missed. Fingers crossed that I've managed to avoid any serious noise issues with the layout and we'll find out in a few weeks.
[[1]]: One of the decoupling caps, despite being directly next to the power connector, apparently wasn't connected to the copper pour according to the DRC. Visually it looked fine to me, but a few vias eventually sorted it.
Old vs New
In order to test circuits, you need test equipment. Luckily my work was getting rid of some old units and I managed to pick up these:
Am I aware that both of these were built before I was even born? Are they probably a fire hazard? Is it worth trying to use equipment that were last calibrated when I was still in primary school? These are all great questions [[2]] but the most important one is, do they even work?
[[2]]: The answer to one of these can be found in my recent purchase of a RCD safety plug to hopefully avoid the magic smoke
Well, mostly. The PSU, a Hameg unit, is actually a dual PSU and sine wave generator. Both are surprisingly solid. The PSU comes with two adjustable outputs and a fixed 5V option between them. The max 0.4A per output might be a problem on some future projects but for most of the stuff I do this is more than enough. The sine wave generator also seems decent. Its a bit fiddly to get a specific frequency you want but my (good) scope claims its outputting what it claims to be. Although the scope I've already got can also generate sine waves, since my current PSU is a) a pain to set up and use and b) only has a single adjustable output, this will probably be something I use a lot.
The oscilloscope is less good. Its a Hitachi VC-6025A and I had high hopes for it. I like the novelty of having a CRT scope and since my good one only has one channel, I thought having a two channel backup would be useful. Initially it seemed to be working fine, but either I've pressed the wrong button or something has gone kaput inside because now it sometimes does this:
What it should look like vs what it usually looks like
There's also the issues that it takes way longer to set up measurements on signals compared to modern scopes, and that I haven't fully figured out how to use the trigger function yet. I may try and revive it in the future but for now it's currently a dud.
Seen and Read
I initially tried reading Cory Doctorow's Red Team Blues. I read Little Brother a long time ago and remember enjoying it, but I really am not a fan of his writing style in this one. Other people seem to have enjoyed it though so maybe it's just a personal problem.
I'm currently on Parable of the Sower which I'm also struggling to read, though for very different reasons. It's a great book but damn is it depressing.
Finally, a few interesting links: