I have only been working with Adruino for a few months now. My first project suddenly came to a full stop.
I have a working prototype on the desk now with an Ebay relay board and an Ebay RS232 Receiver. The system reads serial commands and closes relays per my first Sketch.
I got a lot of help from this forum.
I have had some power problems with my ProMicro Arduino from the start. I didn’t understand the 3.3V vs 5V business. There is a pad that says “Closed for 5V Open for 3.3V”. Well, that doesn’t seem to be necessary. My little test system is running from my Windows USB port just fine. I measure 4.6V at VCC on the ProMicro as well as on the RAW pin. That makes sense to me though I should have a little drop across the input diode.
Ultimately, I want to run the board from 12vdc. My understanding is that I can feed 12v to the RAW pin and the onboard regulator will be happy and make me 5V at VCC. My current schematic is attached.
I made a PCB and tested everything I could before plugging in the ProMicro.
As soon as I plugged in the ProMicro, something snapped near the Regulator and the input diode. I didn’t see exactly what. However, the ProMicro doesn’t work any longer.
I only bought two of these (I have a couple more on order from Ebay) so I am not anxious to blow up another one.
I remember reading someplace that some of the less expensive manufacturers had been delivering ProMicro Leonardos with the diode backwards. It doesn’t look like mine is backwards.
So am I missing something? Shouldn’t I be able to apply 12V to Pin 12 of the ProMicro?
Here is a little description of my schematic…
12Vdc comes in. It heads for Adruino pin 24, my 7805 and to the coils of my 4 relays. My 5V regulator powers my Max232 RS232 receiver.
I have a little dip switch with pullups that I decided to power from the VCC on the Arduino but I know that wasn’t necessary. I should have plenty of power. There are a couple of other LEDs that get directly driven from the Arduino.
The relay drivers are those little mos fets that are designed to driver relays with logic. Its like an npn Q but no resistor or clamping diode is necessary. I have used these many times. They should be fine.
It occurs to me that I can just jumper 5V from my own regulator and power the Adruino from VCC instead of applying 12V to RAW. I don’t know why I didn’t do that originally but that’s not the current configuration.
Is it better for me to run the ProMicro from 5V connected to VCC?
Is the RAW pin really designed to take 12VDC?
I would appreciate any thoughts.