This page describes ideas for an IR proximity sensor.

For a simple proximity sensor, one can drive an IR LED with a modulated signal which matches the subcarrier frequency of an inexpensive reciever designed for IR remote control applications.

For example, the Sharp GP1UW70QS (stock at Digi-Key) works at a subcarrier frequency of 40kHz. If an LED is driven with an on/off modulated square wave of this frequency, the same on/off pattern should be output by the reciever when light is reflected into the receivers photo-detector.

For the proposed application (low-power proximity-controlled LED light) the best solution would probably be a microcontroller with a wake-up interrupt which would power the proximity sensor briefly at a rate of a few Hz, and illuminate the LED lamp when a signal is seen.

PCB Design

Rev 3

Notes: The IR sensor is obsolete. Switch to the GP1UW701QS0F (lead free) which is stocked now but is a 38kHz part. 'NOTE: Needs updated firmware

• ​IR_Sensor_Rev3.sch

Rev 2 PCB

• ​IR_Sensor_Rev2.sch

Rev 1 PCB

• ​Schematic
• ​Layout

• GP1UW70QS IR Detector ​Data Sheet
  • ​Sharp Web Page

• LNA2802L IR LED ​Data Sheet
• ATTiny45 microcontroller ​Data Sheet