Build the Infrared Object Sensors

Submitted by Andy Lindsay on

Parts List:

(2) IR receivers
(2) IR LEDs (clear case)
(2) IR LED shield assemblies
(2) resistors, 1 kΩ (brown-black-red)
(1) piezospeaker
(misc.) jumper wires

Infrared LED and receiver circuit parts

Make Sure It’s Really an IR LED

It’s important to make sure you’re using an IR LED and not a phototransistor.  They look kind of similar.

  • Use this picture as a guide for finding your kit’s IR LEDs.

Diagram comparing the IR Led and Phototransistor parts - the IRLED has a rounder dome

Make it a Mini Flashlight

For this system to work, the IR LED cannot be shining light backwards at the IR receiver.  So, before building the circuit, you need to put each IR LED in the black tube that’s included in your parts kit.  This will make it behave like a flashlight, shining light in only one direction.

  • Insert the IR LED into the standoff (longer tube).
  • Snap the shield (shorter tube) onto the top of the standoff.
  • Tape the shield to the standoff,  but make sure not to let the tape cover the hole where the IR LED’s light comes out!

Circuit

Now, you are ready to build the IR object sensor circuit.

Wiring

  • Set the servo port jumper to VIN, so the servos receive unregulated 6 V from the battery pack (you should be using four 1.5 V AA batteries).
  • Carefully build the circuit in the picture. 
  • Double-check your work against the picture, and especially make sure your IR LED’s longer anode (+) and shorter cathode (-) pins are plugged into the correct rows.

Photo of Propeller BOE with Infrared LED / Receiver pairs

Schematic

This is the schematic for the circuits in the photo above.

Schematic for IR LED / Emitter pairs and piezospeaker on the Propeller BOE