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Opto coupler

Discussion in 'Electronic Basics' started by lerameur, Feb 17, 2007.

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  1. lerameur

    lerameur Guest


    I just finish building a small circuit utilizing an opto coupler, the
    I use an LM331to translate voltage to frequency, that works, but when
    I add the optocoupler in , it do not keep the frequency intact. I mean
    it has huge rise and slow time. Basiclaly If I use a pic chip to count
    the frequency it is basically tell me its high all the time. Is there
    an opto coupler that can react faster ? or this is it. I am trying to
    make a voltage checker circuit using two different grounds.

  2. xrayjuan

    xrayjuan Guest

    What is the frequency? Here is the respond time
    ons Symbol Min Typ** Max Units


    (RL = 100 ??, IC = 2 mA, VCC = 10 V) ton 2.4 ?s

    Non-Saturated Turn-on Time

    Non-Saturated Turn-off Time (RL = 100 ??, IC = 2 mA, VCC = 10 V) toff 2.4 ?s
  3. Chris

    Chris Guest

    Hi, Ken. Try an H11L1 -- it has a data rate of 1MHz and digital open
    collector output. It'll work fine at LM331 frequencies (f(max) <
    100KHz) and can be driven directly by the LM331 output -- the opto-LED
    only requires 2mA to change the logic state on the other side
    (although you should drive it with 4 or 5mA to be safe).

    Be sure to remember the pullup resistor (10K should be fine) from OUT
    to Vcc on the PIC side.

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