Its an Arduino UNO. Apart from the stepper which has its own supply, I have three LDRs using 10K pull-up resistors on A0-A2, a Hall device with 10K pull-up on pin3 and a couple of LEDs on pin 4. Everything works just fine with a regular USB charger running the Arduino and the 9v supply for the stepper. I just wondered if I can get rid of the USB charger and run the Arduino from the 9v supply using the Vin pin.
Geoff