changed timer mode to CTC

this way i can adjust the frequency of the LED
by adjusting a variale OCR1A
update ADC pot experiment

I'm now running ADC in Free Running mode
and reading the vale after the ADC interupt

during the interrupt i'm using the ADC value
to update the value use by CTC

i think this has the side effect that the value in
OCR1A is getting updated during different times in the timer
life cycle which is causing blink times to change