LED on 1sec after power supplied to it

Discussion in 'The Projects Forum' started by Faris1985, Dec 8, 2011.

  1. Faris1985

    Thread Starter New Member

    Nov 29, 2011
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    I want to turn on an LED 1 sec after power is supplied to it and the LED should then be on until power is disconnected. Pls provide the schematics if possible
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    How close does the timing on the 1 second need to be?

    0.9-1.1 seconds OK?
     
  3. T.Jackson

    New Member

    Nov 22, 2011
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    Lol. Round 2 of insanity. You do something with relays then I'll come with something solid state using an MCU.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I abhor relays.

    I'm thinking an RC setup on the base of the driving transistor, which will be +/- 10% on accuracy, but very simple.
     
  5. T.Jackson

    New Member

    Nov 22, 2011
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    I'm thinking about a sanity check for some people.
     
  6. Faris1985

    Thread Starter New Member

    Nov 29, 2011
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    Yeah close to 1 sec
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    A very similar project...

    Power led slot turn

    If you have any questions about it post them here, on this thread.
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I think this is more-or-less what was suggested above. I have NOT done the math on the timing, the cap and resistors, I just took a wild guess.
    [​IMG]
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    With those base resistor values I doubt it will get close. In the end the transistor needs to be in saturation.

    I don't know if the OP is wanting fading or not, which is the circuit I pointed to. If just a delay a 555 or other Schmitt Trigger is probably the ways to go, as it addresses the fundamental gain issue.
     
  10. sheldons

    Active Member

    Oct 26, 2011
    616
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    this can be built quite small ,you may need to play with the values of the timing components to get what you need....
     
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