IR detection "meter"?

Discussion in 'The Projects Forum' started by gee_emm, Apr 28, 2008.

  1. gee_emm

    Thread Starter Active Member

    Jan 16, 2008
    Im trying to make an IR detection circuit. Ive made one using a comparator,LM339, wich flashes an led when I use a remote control.(remote is just for testing) BUT, what Im trying to really make, is one that would show the strength of the signal. A red LED (weak signal) yellow (better) green LED (strong signal).Or something of that nature. Its basically for testing, and measuring, where the IR on automatic doors are located. Any suggestions or links is very appreciated. Thanks.
  2. gee_emm

    Thread Starter Active Member

    Jan 16, 2008
  3. mik3

    Senior Member

    Feb 4, 2008
    You can use an amplifier to produce a signal proportional to the IR receiver diode current (how much infrared radiation hits the led). Then if you like you can use a microcontroller to read this signal and according to its value to determine which led (red, yellow or green) to light. if you dont want to use a microcontroller you can use three comparator op-amps and set each one with different voltage levels to compare. So, you will compare the signal from the amplifier with one of these set voltages on the comparators simultaneously and light the corresponding leds.
    if you use a microcontroller you can light more leds to give you better accuracy of the signal's strength with less circuitry.
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    Look at the TAOS light to voltage converters. They have more response than you want (IR to UV), but a filter might be simple to come up with. Mouser has them, starting at $1.27.

    Filtering the incident light may be necessary in any case. It would allow you to get an idea of the quality of the IR signal, and then see how much it gets degraded by ambient sources.