I'm tinkering a bit with a new printed circuit board I made and I already lost two boards (one ESP32 and one Arduino WiFi 1010) and I'm stumped because I don't even know where to start to look for a cause - it just doesn't make sense to me. Let me explain...
Here is the circuit diagram with a portion marked that I believe to be unrelated to what happened (I might be wrong):
(power supply set to 24V
and 0.1A
, the thing in the middle [microcontroller] is an ATTiny2313
, WAGO
is a wire-to-board connector)
What's a bit sketchy I would say is that the ground of the Arduino WiFi (which is provided via USB) is connected to my floating lab power supply. It also has an earthing terminal as in the picture, but it is not connected to anything.
The laptop is running on battery, so it is not connected to mains voltage in any way.
Now I can (sadly) only recall what happened in terms of when I realized (through coincidence) that my Arduino got unusually hot *. So hot in fact, I'm pretty sure it's done (I used it as an ISP programmer and now the arduino is not recognized anymore).
*this happened not immediately but after some time ; I can't tell how long.
Anyway, this is less about the dead Arduino (and ESP) but more about what went wrong because, as previously stated, I have no idea where to even begin looking for something that might have caused this.
The DC-DC converter might have something to do with it, although I can't imagine how it might have damaged my Arduino.
The problem is, I would like to investigate (i.e. replicate) what happened, but I don't want to risk losing another Arduino Board because they are really expensive (+40$).
Why do I not understand what happened?
1.) I only connected GROUND between the two circuits, so it cannot (likely) be something to do with the +24V rail or +3.3V rail.
2.) MISO, MOSI and SCK are I/O pins that I don't think can provide that much current to my Arduino (my Microcontroller did not get hot at all).
3.) RESET is a bit different since IT IS connected to the +3.3V rail but through a 4.7k resistor.
In the end, I'm really hoping I'm missing something obvious here.
Any pointers or common pitfalls that one might fall into when using a USB powered device with another device that isn't on the same supply rail?
Edit: And even if you can't explain what happened, do you have any ideas on how I could (potentially) replicate my circuit in a "safe" or "safer" way?