I have a circuit with two supplies. A 19v supply for stepper motors, and a 5v supply for driving the ATMEGA644, 3 stepper motor driver daughter boards, a bluetooth LE daughter board, and 2 ws2812b rgb leds.
With two supplies everything worked, but I really wanted to get it down to just one supply. So I did another version of the board using just the 19v supply and a VX78-500 switching regulator. I used their recommended input and output caps. (But not the low noise version that include some extra inductors) .
I have a 100uf electrolytic on the 5v rail. Not 100% sure if that's a good idea but it's well below the max capacitive load for the VX78-500 which is 680uf and I thought it might help with noise.
I also have 3 100uf electrolytic on the 19v line next to the stepper driver boards for the same reason.
When I first turned things on I noticed the WS2812b'd flashed slightly but everything was fine. That didn't happen on the 2 supply version of the board. However on maybe the 3 or 4th time I turned it on the bluetooth LE daughter board died. Which is kind of surprising because it's got its own on board 3.3v LDO regulator.
I don't know that much about supply best practices/inrush current, etc. I knew my new setup would be noisier using a switching supply/being down stream from the same supply as the steppers. Any ideas what is going on? That flashing makes me think there's a bad spike happening at switch on time. It seems weird that the atmega644 is still ticking but the BTLE daughter board died. How do I trouble shoot this?
Are those 100uf caps just a bad idea in general? Does my circuit need some other form of protection?
Those daughter boards are $19 so I don't want to blow out too many of them in a search for the solution. Here is a pic of the PCB. I'm sure I'm just making some noob mistake, but I'd really like this 1 supply version to work.
Oh ignore where that says 12v, it's really 19v. blush Thank you for your time.
Here are the two sheets of schematic as well.