infra red

Discussion in 'General Electronics Chat' started by shankbond, Feb 12, 2008.

  1. shankbond

    Thread Starter Active Member

    Nov 4, 2007
    how do i link infrared red with detecting distances ,
    like i want to detect adistance of say 5 cm. at what (time duration of pulse) should i send the infra red at what time period?

    thank you
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    The speed of light is close to 300,000 km/sec. If you want a pulse to be able to measure that distance, it will have to be way under a picosecond in length. Timing is even worse.

    Sound might be a possibility instead.
  3. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    you would need an IR transmitter which will be composed of a signal generator and IR LED driver. your signal generator can be a 555 timer configured as an astable multivibrator to generate an output of say 12khz and the timers output drives the IR LED through a switching driver transistor.

    As to your IR receiver, the signal emitted by the IR LED will be detected by a matching infrared receiver diode. since this signal is weak it has to be amplified by a preamp either with the use of transistors or opamps to the same level as the transmitted signal to ensure reliable decoding.

  4. Audioguru

    New Member

    Dec 20, 2007
    Sharpe makes an IR receiver IC that uses detected signal strength to measure short distances. The reflective surface type and brightness of the transmitted IR beam affect the accuracy.
  5. scubasteve_911

    Senior Member

    Dec 27, 2007
    What method of measurement do you want to implement???

    - Time of Flight / Phase Shift Measurement is out of the question, your clock would need to be in the several GHz range, or your phase shift circuitry to resolve somelike like 0.001 degrees

    - Reflective intensity, which basically relies on how much light is being recieved and correlates to distance, which is bad because it is surface dependent

    - Position sensitive detection, uses special sensors that are difficult to interface, unless done so by the mentioned sharp distance modules, but a lot more immune than reflective intensity sensors to surface variations