replace pushbutton with IR trigger

Discussion in 'The Projects Forum' started by singularity, Nov 24, 2013.

  1. singularity

    Thread Starter New Member

    Nov 24, 2013
    3
    0
    Hi all,

    I am new to design and can't seem to get my circuit to work. I am trying to replace a push button with a IR hand trigger. Please have a look at my attached circuit and let me know what you think. Thanks in advance for any info.

    The bush button will be attached in parallel to pin 4 and pin 3 of the optoisolator.
     
  2. singularity

    Thread Starter New Member

    Nov 24, 2013
    3
    0
    IR1 = IR emitter

    Q1 = photo-transistor

    please ask me questions if necessary. I am not sure if I have explained it well enough.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Move the 10KΩ from between the collector of the IR detector and the base of the NPN
    to
    between the collector of the IR detector and the positive rail.

    Connect collector of the IR detector directly to the base of the NPN.

    Delete the 330Ω

    Test the circuit. Be prepared to experiment with the value of the 10KΩ to control sensitivity (Likely higher, no Less than 2K).
     
    Last edited: Nov 24, 2013
    singularity likes this.
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Here is a sim of two ways of doing it. Both methods work about equally.

    The dashed box simulates an IR detector, where its base current is modulated by how much IR it receives. I am taking a WAG at its sensitivity. The LED is a proxy for the Opto input.
     
  5. singularity

    Thread Starter New Member

    Nov 24, 2013
    3
    0
    Thanks for your input.

    I tried as you suggested. I used a pot to set the value (about 11k) for the collector resistor of the IR detector. Works very well.
     
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