SparkFun Forums 

Where electronics enthusiasts find answers.

For the discussion of Arduino related topics.
Hey All,

I am currently using an Arduino Pro Mini with the FTDI Basic Breakout. I have my circuit connected to a bunch of buttons, LED's, sensors (hall and IR), and stepper motor driver board (the A4988 Stepper Driver from Pololu).

I have my circuit on a solderless breadboard with a 12V benchtop power supply connected to the breadboard and RAW pin (on Pro Mini) while the FTDI cable is plugged into the Arduino Pro Mini (and USB port on my computer). I have the left side rails of the breadboard connected to 12V and GND. I then take the Vcc(5V) from the Arduino Pro Mini and connect it with one of the right rails on the breadboard.

With everything connected (separate 12V and FTDI cable), my code runs GREAT! Everything functions as intended.

BUT when I remove the FTDI cable and power the RAW pin with 12V, the entire circuit is doing crazy things and my code is obviously not running. I cannot figure out if I have too much voltage, or what is happening. I have a common ground between the GND's on my power supply and Pro Mini and the A4988 (i.e. all grounds tied together).Any suggestions?

Thanks in Advance,
Hey All,

I see that many people have looked at my post, but nobody has replied. I am beside myself that I cannot figure out what is happening. With 12V from my benchtop power supply and the FTDI programmer connected to the Arduino Pro Mini, everything works fine. But as soon as I disconnect the FTDI, nothing works right. I turned the voltage down to 10V and it seems to "work" better, but it keeps stopping and restarting. Anybody?

The voltage regulator on the Pro Mini was probably overheating with 12V on RAW. 6-7V is better, or power the Pro Mini directly from a 5V regulated source, via the Vcc (5V) output.

Do not apply 5V to the RAW pin, as the on board regulator won't work properly.