Introduction: Simple Infrared LED and Photodiode Tester

This is a simple Infrared LED and Photodiode tester using Arduino-compatible microcontroller.


I received a new batch of IR LEDs and IR photodiodes. I need to test them before signing them off. I have limited tools at home. So I devised a simple test for the IR LEDs and the IR photodiodes using Arduino-compatible microcontroller. In my case, it was a Wemos D1 Mini R2 ESP8266.

Bill of Materials:

1 pack of IR LEDs to be tested

1 pack of IR photodiodes to be tested

1 Arduino-compatible microcontroller (Wemos D1 Mini R2)

1 Resistor 6k Ohm

1 Oled Screen (i2c) - optional

1 x 1.5V battery (LR44 coin cell)

1 x mobile phone with camera

Jumper wires

Step 1: Part 1: IR LED Test Rig

Can be used to test IR LED without any
other electronic components except a camera.

Turn off the lights.

Connect IR LED to the 1.5V battery. (Make a throwie or dupont M-F jumpers)

Aim IR LED to a white surface (e.g. paper).

Turn on phone camera and look through the camera at the IR LED.

You should see a pinkish or reddish light reflected on the paper.

Note: I used old LED strip connector (female) to to make it easier for me to switch LEDs.

Step 2: Part 2: Testing IR LED and Photodiode

This setup allows easier testing of both IR LED and IR photodiodes.

Connect the IR photodiode to an analog
input of an Arduino-compatible microcontroller. The photodiode should be connected to a pull-down resistor.

For mobility and ease of use, I also included an OLED screen to display the readings. The OLED screen is purely optional. You can just use your Serial Monitor on Arduino IDE to get your readings.

  1. Setup the electronics. I am using Wemos D1 mini R2 (ESP8266). But this works with UNO as well. See circuit diagram.
  2. Start up Arduino IDE.
  3. Load the code.
  4. Note the base reading. Mine was 1-2.
  5. Aim the IR LED from Step 1 above at the tip of the IR photodiode. The reading should increase.
First Time Authors Contest 2016

Participated in the
First Time Authors Contest 2016

Arduino Contest 2016

Participated in the
Arduino Contest 2016