• The logical circuit in the bottom right allows to drive three digits depending on the states of only two pins PB3 and PB4.
  • The capacitor circuit allows to couple the clock and reset lines of the counters on a single avr pin, PB1. A long 1 signal will load the capacitor and trigger the reset signal. A diode was necessary but I don't really know why actually...
  • PB0 select the counter to enable, A or B.
  • Measurement of the voltage is done on PB2.
  • (Sorry if this is a bit succinct, this my first post ever on a website...)
  • (I also hope that the .sch file is correct, I am also new to KiCad...)
  • I added the part of the circuit that is being measure: a linear voltage regulator that I feed with a laptop charger output (~18V). Another regulator provides the 5V for the AVR