All in one Infrared Emitter and Detector Module
This module integrates 2 infrared emitting LED’s and 2 IR detectors.
It works by continuously sending a 38 kHz beam of IR light from both LED’s. As the robot approaches an obstacle, the IR light reflecting off the object will cause one or both of the detectors to send a LOW signal to the microcontroller. This in turn will cause the robot to slow or stop one or both drive wheels depending on the level of detection.
In order to avoid false positives and sensitivity to different light conditions, I used a pair of PNA4602M IR detectors. The great thing about these detectors is they only respond to a 38 kHz signal. So even in varying light conditions, you can get fairly consistent performance. Note that the PNA4602M has become obsolete and you can find a good suggestion for its replacement at David Cook’s site.
The circuit design is fairly simple and doesn’t take up much real estate. I wanted to have all of the traces on one side so I could etch it using one-sided copper clad. I ended up only needing one jumper wire to complete the circuit, which is pretty good for me. Usually I end up with a bunch.
- R1 = 22K ohm Resistor
- R2 = 10K ohm Trimpot
- R3 = 190 ohm Resistor
- C1 = .001 uF Ceramic Capacitor
- C2 = .01 uF Ceramic Capacitor
- C3 = .01 uF Ceramic Capacitor
- IC1 = LM555N or any 555 Timer
- LED1 and LED2 = 940 nm IR Emitters
- IR Detectors = PNA4602M or TSOP4038
- Optional Connectors: 1 for power/ground, and 2 output/ground (Note that you probably only need 1 pin connectors for the outputs since the Power connector carries the ground).