Hi, I have used a UNO and Leonardo many times in the past. I have a project I used on the UNO with a 12V regulated (I say regulated because the multimeter reading is 12.00V and does not change) power supply going to the Vin, everything works fine. To save money I wanted to replace the UNO with a pro mini. The pro mini works just fine when it gets it's power over the USB, but when I hook up the 12V to the "RAW" pin it does not work correctly. The power flashes on and off. Can I hook the 12V to the Vcc pin and not damage anything assuming the power is regulated (not sure if it is regulated or not)? Could someone point me in the right direction? Thanks!
The VCC can take 5V, assuming it is a 5V pro mini. That said the raw pin should take 12 V. Normally I would expect it to behave the way you have it if there was a short in the circuit.
The RAW is the power input, and VCC is the output of the onboard voltage regulator. VCC is 5V for a 5V 16MHz version and 3.3V for a 3.3V 8MHz version.
So you may never apply 12V to VCC.
Everything is small on the Pro Mini board, even the voltage regulator and it can not handle a lot of heat. It has to regulate the 12V to 5V, so it has to waste 7V into heat. That might be too much for the little thing.
I think everything is fine when you use a 7.5V power supply to the RAW pin. Or you might try a 5V power supply directly to VCC.
I tried both a 9V and 5V power supply as well, and it did not work. Keep in mind, it works fine when it gets the power over the USB.
Sounds like a regulator issue then. Can be hard to replace being so small. Can you just use a 5V wallwart? That's what I do. Or 3 AA batteries.
http://www.dipmicro.com/store/DCA-0510
Add a couple wire to a barrel jack
http://www.dipmicro.com/store/DE1573
Maybe a panel mount connector
http://www.taydaelectronics.com/hardware/dc-power.html
or add a barrel jack adapter
if you don't want to cut the connector off the regulator.