I measured the shield (gnd) of the USB cable and the body of the printer. There was 4.8V?! Which means the power of the USB goes to the printer and then back trough the shield (gnd) of the USB.
Because it was 5V I was sure the Ardruino had somehow contact with the body of the printer. Turned out one of the nuts that holds the Ardruino in place touches a metal pin on the bottom of the board (which wasnt the GND). So I had a loop..
Just printed a tiny washer and the problem was solved!! (Smaller nuts would also solve it but thats more work ;-)).
Thanks for the advice, you really helped me out here.
Because it was 5V I was sure the Ardruino had somehow contact with the body of the printer. Turned out one of the nuts that holds the Ardruino in place touches a metal pin on the bottom of the board (which wasnt the GND). So I had a loop..
Just printed a tiny washer and the problem was solved!! (Smaller nuts would also solve it but thats more work ;-)).
Thanks for the advice, you really helped me out here.