I'm working on a basic application with a microcontroller controlling several components including a:

• 12V DC pump (Darlington array)
• 12V PWM fan (Darlington array)
• humidity sensor (I2C)
• and LED controllers (SPI)

Online circuit can be found here.

I've setup and tested each component individually to ensure they work given my circuit. From there, I transitioned from breadboard stage to a more intermediate stage using a protoboard along with various wires soldered in the right place.

After placing everything into a small housing, I recently went to connect everything only to end up frying the microcontroller and the UBEC. Since all the components were previously working, I'm not certain exactly what caused it except for perhaps a short caused by my mess of wires on the protoboard.



I know general questions like this are generally not within guidelines, but I'm just looking for insight into whether I'm completely off the mark somewhere. I'd prefer not blowing things up anymore :-/

 

Did you ensure that all relative ground connections were correct.
It pays to use a decent ground plane.
Max.

 

Apparently a short somewhere.
Did you double check all wiring after the failure to make sure everything was connected correctly?
The next time, connect things up one at a time and carefully check the wiring before powering up.

Where is the 3.3V for the processor coming from?
Whats the purpose of D2?
You might consider a buck converter that is short protected.

 

Did you ensure that all relative ground connections were correct.
It pays to use a decent ground plane.

By that do you mean that all grounds are properly connected together? For the time being this has all been in breadboard, so I don't have a ground plane.

 

Apparently a short somewhere.
Did you double check all wiring after the failure to make sure everything was connected correctly?
The next time, connect things up one at a time and carefully check the wiring before powering up.

Where is the 3.3V for the processor coming from?
Whats the purpose of D2?
You might consider a buck converter that is short protected.

- 3.3V is the output from the uC
- wasn't sure if D2 was needed, someone mentioned to be previously that the fan connection seemed suspect and that I might risk putting 12V into the pin 12 of the uC

 

3.3V is the output from the uC

Does it go anywhere?

 

Does it go anywhere?

It's used to power the LED driver and the temp/humidity sensor at the bottom of the schematic.

 

Just an aside, are you using any of the other ULN drivers? If not consider a single logic level mosfet.
Max.

 

Just an aside, are you using any of the other ULN drivers? If not consider a single logic level mosfet.
Max.

Currently no, but I opted for the 8-channel for flexibility in controlling other additional devices.