Wiring LED Sensor

Wiring the LED to the nRF52840 feather is very straight forward.

The LED will generate a voltage when it detects light. Therefore, the LED anode is connected to A0 which is 1 of the 6 analog to digital pins on the Feather that can read voltages and convert them to a 16 bit value. The Feather’s ground and the LED cathode are connected to a ground rail on the breadboard. As is, this circuit would be very noisy and unreliable. Therefore, a filter is added which is comprised of an 82nF ceramic capacitor and a very weak 15M Ω pull-down resistor. Both are placed between the LED anode and ground. That’s all it takes for the detector circuit. The Feather should now be able to read a voltage change on A0 when a bright blue light hits the attached green LED.

This guide was first published on Oct 16, 2019. It was last updated on Oct 16, 2019. This page (Wiring LED Sensor) was last updated on Nov 13, 2019.