The first component I tackled won't be used directly in the printer at all. It's a basic power rail that takes the 24V from a Meanwell power supply and turns it into 12V, 5V and 3.3V.

For this I used through-hole power conversion chips, and through-hole capacitors that were recommended on the data sheets. I could easily have breadboarded this, but decided to use this as an opportunity to test doing things "right." So I designed the circuit in KiCad, did the routing, and ordered boards from Osh Park.

Osh Park surprised me! I hear all the ads for JLCPCB, and it's China, so I expected it to be way cheaper than anything in America. But (without getting too political) I'd rather not work with China any more than necessary, so I decided to see just how much of a tax I would pay to work with Osh Park. It's virtually the same price for my specific use, once you factor everything in. JLCPCB was something like $5 for the board, and like $10 for shipping. Osh Park was something like $15 for the board and free shipping. For a $0 tax, I will gladly take the American option.

So the boards arrived, I wired everything up, did the very basic soldering of through hole components. So far so good. I turned on the Meanwell, and started to plug the board in and got a very small spark. Eeks! Gathered my breath, started to plug it in again and got another small spark. After some careful investigation, the power converters weren't getting hot, the sparks were very small, I decided to see how bad it really was. Plugged it in all the way, no continuous sparking or anything. Nothing was getting hot. Broke out the multimeter and everything is at the right voltages.

After some investigation, it all makes sense. The data sheet for the power converters want capacitors from in to ground and from out to ground to filter noise. Makes sense. But capacitors start off as basically as short when they are empty. So for a fraction of a second, when I plug it in, I'm shorting my Meanwell's +24 directly to ground, then the cap charges quickly!

It shouldn't harm anything, but it's a bad experience for the user, so in future designs there will be a resistor in series. A small resistor should be enough to not spark, and it won't meaningfully affect the power circuit, especially if my first drop is from 24V to 12V. At least that's the theory. Future boards will test that theory!