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IR Sensor

Discussion in 'Sensors and Actuators' started by Abinaya Sindhu, Nov 3, 2014.

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  1. Abinaya Sindhu

    Abinaya Sindhu

    5
    1
    Nov 3, 2014
    Hi,

    I am a newbie. Can anyone please tell me how to connect an IR Led as a transmitter and other as a receiver for obstacle detection.

    Thank you.
     
  2. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Hi, and welcome to the forum.

    What kind of detector are you using? This might be a simple photodiode or phototransistor or it might be a complete detector + demodulator designed to operate at a specific frequency. The transmitter and receiver circuits are different depending on which type.

    Please send a link to the specific receiver and the IR LED for more help.

    Bob
     
  3. Abinaya Sindhu

    Abinaya Sindhu

    5
    1
    Nov 3, 2014
    Hi,
    Thanks for your reply. I'm using a simple photodiode. This is my circuit. I'm getting the output as high always ( even when there's no obstacle). Where am I wrong? Please help.

    Thank you.
     

    Attached Files:

  4. davenn

    davenn Moderator

    13,655
    1,888
    Sep 5, 2009
    do you have an IR filter over the photodiode
    if not ambient light is going to stop the circuit working
     
  5. Abinaya Sindhu

    Abinaya Sindhu

    5
    1
    Nov 3, 2014
    I don't have an Ir filter. Do I need one? Is there any problem with my circuit? Thanks.
     
  6. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Yes, a photodiode cannot pass enough current to pull a 3K resistor low. What are the specifications of the photodiode? You will need to amplify the signal or use a phototransistor, which has the amplification built in.

    Bob
     
  7. Abinaya Sindhu

    Abinaya Sindhu

    5
    1
    Nov 3, 2014
    I used 120Ω instead of 1k and 220Ω instead of 3k and it's working. Thank you..
     
  8. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    I doubt that. If your photodiode cannot pull a 3K resistor close to ground, it certainly cannot pull a 220Ω resistor to near ground. If it is working, you have a phototransistor, not a photodiode.

    Bob
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,270
    Nov 28, 2011
    I suspect it won't be very reliable if ambient light can get on it. You need to use modulated infra-red. Then you can use a TV remote control receiver module. When you discover it doesn't work properly, come back and ask about modulated IR.
     
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