I' designing a stepper motor driver. I'm going to power the board and the motor via 12V, but the ICs use 5V. So this is not a problem at all, but I'm not sure about the different GNDs of the Arduino and the driver board. The data goes via 5V IOs from the arduino to the board, so I guess I need a kind of GND connection back to Arduino, I can't just tie it to the 12V power supply ground, right? But where do I start? I'm using a L6506 and a L298, both are connected to 5V. But I also don't want to power the ICs from the Arduino.
This is very standard. There is generally no problem connecting the
gnds together on boards that both work off low DC levels like
5V and 12V.
However, what you generally want to do is to make sure the 12V
battery/supply for the motors is connected directly to the motor
board, rather than your trying to pull it through the Arduino board,
eg, via the Vin header pin.
If you want to use the same 12V supply for both motors and Arduino,
tie it to the motor board first, and daisy chain over to the Arduino bd.
However, in general, it's better to power the Arduino from a
different supply, so the motor noise has less chance of disruptiing
Arduino operation.
Common the grounds, just make sure motor current does share a ground wire with Arduino.
I think he means "does NOT share ...". You really want to keep the motor
"currents" confined to the motor-board + motor battery ckt, and the ground
wire between the bds carrying only a small signal current.
Oh that easy! I thought powering the Arduino over USB (sorry, forgot to mention) AND external source would be a problem. So I just add 5V and GND pin for the arduino on my driver board. Thanks
