STRAY PIN CAPACITANCE EFFECTS ON SIGNAL READING COUPLED BY OPTOCOUPLER ON MICROCONTROLLER BOARDS

Abstract

Reading high frequency signal could have possibility effecter by the internal
capacitance from microcontroller pins. Study case is between Arduino and encoder coupler
with optocouplers. High frequency signal is struggle to high logic due to slower rise time.
Turns out slower risetime caused by internal capacitance causing 1st order response system,
by adding pull-up resistor on input pin, risetime could be reduce. As final result, adding
pull-up resistor does affecting the rise time, but the there are still other factors beside
internal capacitance.