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fast optical switch circuit to turn on 3V 1A supply - please help

Discussion in 'General Electronics Discussion' started by Stickyfeatures, Oct 25, 2017.

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  1. Stickyfeatures

    Stickyfeatures

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    Oct 24, 2017
    Hi folks, it's been ages since I did any electronics but I'm in need of a circuit to be able to switch on a 1A 3-Volt load as fast as possible.

    Here's the requirement summary:
    • Operating from 3-volts DC line
    • Switching on a 1 amp load as energy efficiently as possible
    • As fast a switching circuit as possible (must be less than 1 microsecond)
    • No need for proportional output; just digital on/off at any light level
    • Minimum component count preferable (discrete IC is fine if not too expensive)
    • High output when there is a light input
    If anyone can give me some ideas of components or circuits that would be great.

    (sorry to be asking rather than offering help on my first post :(
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009

    opto-coupler
    solid state relay

    kinda the same thing .... a solid state relay is just an opto-coupler on steroids ;)
     
  3. Stickyfeatures

    Stickyfeatures

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    Oct 24, 2017
    Sorry, I should have said that this is to work off an external light source so I'm not sure an optocoupler is needed. Do you have any components in mind Davenn so I can check the specs please?
     
  4. 73's de Edd

    73's de Edd

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    DAMN SAM ! . . . . . .Would you please TRIPLE confirm that third spec down as being less than 1 MICROSECOND.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009

    that doesn't change my response

    google opto-coupler and solid state relays and see how they work
     
  6. BobK

    BobK

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    I don’t think you will find an optocoupler ir SSR with 1 microsecond response time.
    I think a crcuit based on a photodiode will be required.

    Bob
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    and both of them use photo-diodes of types ;)
     
  8. davenn

    davenn Moderator

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    Sep 5, 2009

    but I agree with bob and edd

    <1uS is a huge ask!!!

    why so fast ?
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    When you say "switched in less than 1 microsecond", do you mean 1us from when light reaches a certain intensity, or that the load must be switched from off to on in less than 1us?

    Do you have anything other than the 3V you need to switch as a voltage to power the circuit?
     
  10. BobK

    BobK

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    Jan 5, 2010
    Actually, they use phototransistors.

    If you look at the specs, the photodiodes are way faster, measured in 10s of nanoseconds, whereas phototransistors are typically several microseconds.

    The trick would be getting the amplification needed without increasing the delay to over 1 uS.

    Bob
     
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