How to: drive common cathode led with Arduino?

Using Arduino General Electronics
9

Sorry for the confusion Grumpy_Mike
I've corrected the schematic in my former post to reflect the circuit I'm currently having :slight_smile:

  • When the Arduino I/O is high, I measure 15V (probing points marked in former post), when it's low I measured -9.7V and just before at the same conditions -15, The value drifts a little, I don't know why.

If I remove the led, and still measure at the two points marked, I measure 15V when Arduino I/O high, and 0V when low :slight_smile:

Best regards
Joe