IR Sensor using lm324

Discussion in 'Homework Help' started by cly_1018, May 13, 2012.

  1. cly_1018

    cly_1018 Thread Starter New Member

    Joined:
    Jan 11, 2010
    Messages:
    2
    Hi All,

    I need help on the IR Sensor circuit using lm324 comparator~the distance between transmitter and receiver is 20cm.
    1) How to combine both circuit together? Is the circuit design correct?
    2) How to measure the output voltage when the IR sensor is in blocking condition and non-blocking condition?

    IMG_0210.jpg

    Thanks.
  2. Bill_Marsden

    Bill_Marsden Moderator Staff Member

    Joined:
    Mar 24, 2008
    Messages:
    19,316
    Location:
    Dallas, TX (GMT-5 w/ DST)
    The design is flawed, seriously so. You have the - input connected to gnd. This will create a anomalous condition for the op amp, which you are trying to use as a comparator. With the input at ground there can never be a cross over of the voltages. There needs to be a small resistor to raise that level off the ground, as the + input can never go below the ground level.

    You have another problem in using the LM324. This is an op amp, most op amps have a problem with their inputs going near either power supply level. Using a LM393, a true comparator, is a much better choice, though don't forget the pull up resistor (10KΩ typical) on the output.

    When using 4 op amps or comparators do not forget to ground the unused components inputs, to prevent unwanted oscillations.

    High Speed Op Amp Query

    The LM358 is an op amp that is designed for its input to go very near ground.

    Bill's Index
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