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Optoisolator Circuit

Discussion in 'General Electronics Discussion' started by WaltP, Jun 16, 2017.

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  1. WaltP

    WaltP

    10
    0
    Jun 16, 2017
    Hi. I'm a bit of a newbie slowly working my way up the learning curve. Could someone please help with a circuit and choice of transistor to increase the current output from a proximity sensor (LCZ260) in order to trigger an opto isolator - I'm using a 6N137. The proximity sensor output at 5 volts is .5 to 1.1 ma depending on resistor choice which I need to boost to around 10 ma in order to trigger the 6N137. Thanks in advance.

    Walt
     
  2. AnalogKid

    AnalogKid

    2,496
    718
    Jun 10, 2015
    Can't draw a sch right now.

    2N7000 or 7002 MOSFET:
    Sensor output to gate
    Source to GND
    Drain to 6N137 cathode
    6N137 anode to 220 ohm resistor.
    220 ohm resistor to +5 V.

    2N4401, 3904, 2222 Bipolar transistor:
    Sensor output to 1K resistor
    1K resistor to NPN transistor base
    Transistor emitter to GND
    Collector to 6N137 cathode
    6N137 anode to 220 ohm resistor
    220 ohm resistor to +5 V

    ak
     
  3. WaltP

    WaltP

    10
    0
    Jun 16, 2017
    Many thanks, I'll give it a run.

    Edit: Happen to have a 2N7000 and it worked quite nicely. Changed to a 560 ohm resistor which put me at 10 ma. Again, thanks for for help. If you feel like responding again, is there any advantage or disadvantage to a mosfet. If I interpreted the datasheet correctly, response time seems faster at lower voltages which, I think, would be in the 20 nanosecond range. Are bipolar transistors faster?

    Walt
     
    Last edited: Jun 16, 2017
  4. Minder

    Minder

    3,076
    657
    Apr 24, 2015
    One advantage of a mosfet is it offers high input impedance over bi-polar.
    M.
     

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  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,489
    2,830
    Jan 21, 2010
    One disadvantage of the MOSFET is it's high input impedance.

    Ok, that's a bit tongue in cheek, but the differences between components can be advantageous or detrimental. They are almost always a double edged sword.
     
  6. Minder

    Minder

    3,076
    657
    Apr 24, 2015
    I vary rarely use bi-polar transistors any more if I can help it.
    M.
     
  7. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Bipolar transistors behave better when doped with Lithium.

    Bob
     
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