Comparator LED Indicator

Discussion in 'General Electronics Chat' started by artmaster547, Aug 29, 2017.

  1. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
    7
    Hi All
    I am trying to create a circuit at the output of a comparator, when the output of the comparator is high (3v3) I want and LED to turn on, but then I want this LED to remain on after this even regardless of any changes to the output of the comparator. Can someone please suggest what I could use, provide LTSpice simulations, any guidance help would be appreciated. I am also trying to reduce the amount of components I need to use as much as possible for this circuit if an IC already exists that already does this any suggestions would be greatly appreciated.

    Kind Regards

    Art
     
  2. jayanthd

    Active Member

    Jul 4, 2015
    698
    64

    OpAmp with Flip-Flop.
     
  3. Marley

    Member

    Apr 4, 2016
    249
    61
    Comparator plus latch (to be precise). But how will this latch be reset to switch the LED off or does it stay on forever?
     
  4. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
    7
    Hi I want it to stay ON until I guess the whole power supply to everything in this circuit is reset
     
  5. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
    7
    Hi there would you mind providing a schematic of sorts? Could you also suggest what kind of Flip-Flop IC I should use?
     
  6. jayanthd

    Active Member

    Jul 4, 2015
    698
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    What is your Vref for Comparator ?
     
  7. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
    7
    around 3V
     
  8. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
    7
    I'm using a digital comparator so Output is 3v3
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    8,751
    2,020
    What are you comparing? It may be possible to use one Schmitt trigger IC (e.g. CD4093) as both a comparator and a latch.
     
  10. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
    7
    So I am using this principle across various circuit it will be comparing voltage and current measurements that have a range of 0V-3V3, and I will be setting reference voltages myself, these comparators will be used as trips that go to a microcontroller but this particular uC only has three trip inputs so I'm ORING all these trips together, so that is why I was thinking of using LED's as a way to indicate which trip went off.
     
  11. jayanthd

    Active Member

    Jul 4, 2015
    698
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    Why don't you use ADC of uC (1 channel) with ADG731 (analog multiplexer spi interface).?
     
  12. artmaster547

    Thread Starter Member

    Jan 6, 2016
    393
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    I was considering that but kind of want to avoid that I would prefer something that was more of an indicator in terms of hardware i.e. an LED
     
  13. jayanthd

    Active Member

    Jul 4, 2015
    698
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    Here is the quick circuit which I made. Hope this helps. Extract it using winrar or winzip and view the video in VLC Player.
     
  14. DickCappels

    Moderator

    Aug 21, 2008
    4,963
    1,512
    If the negative-most range of the input signal (Vin) does not go below V- on the compariator + 1 diode drop, you can just use a diode to get a large amount of hysteresis to keep your LED on.I may be reading Alec_t's mind.

    upload_2017-8-29_18-56-20.png
     
  15. jayanthd

    Active Member

    Jul 4, 2015
    698
    64
    With my circuit use 1N4372A (3V zener).
     
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