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fading red eyes

Discussion in 'Electronic Basics' started by [email protected], Aug 25, 2006.

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  1. Guest

    Hi all, I'm moderately knowledgable about electronics but have
    forgotten a lot ;)

    I am trying to use the fading red eyes circuit and all I get is the
    LEDs stay on, no fading or anything. I have checked all the connections
    with no result. Hoped someone here might know what could cause this

  2. Guest

    If it is simpler, all I really do is for the LEDs to illuminate slowly
    when turned on and fade away slowly when switched off. By putting the
    resiter and LED in series across a 1000 uF cap but I can't get them to
    illuminate slowly,
  3. Eeyore

    Eeyore Guest

    What is this " fading red eyes circuit " ?

  4. Greg Neill

    Greg Neill Guest

    You'll need a resistor between the power supply and
    the cap/LED/resistor combo -- there has to be something
    to drop the voltage across while the capacitor charges.
  5. Guest

  6. Guest

    Greg Neill wrote:

    any suggestions for value, I tried that but it just stopped it working
    completely, or perhaps charging toooo slow.

    I'm using a 1000uF cap and a super bright blue 5mm LED with 9v supply.

    Thanks for the help.

  7. ehsjr

    ehsjr Guest

    We can't see what you have done. Post a picture
    of what you built. Also, replace the blue LED with
    red leds, at least until you get the thing working
    as per the Bowden design.

    Next: if you followed the schematic, either the transistor
    is always turned on, or is mis-wired, or is shorted. You
    can disconnect the wire from pin 1 of the 1458 to the base
    of the transistor - if the leds still glow, your transistor
    is shorted or wired wrong. Do you have a DMM?

  8. Tom Biasi

    Tom Biasi Guest

    How can a "super bright blue 5mm LED " make fading RED eyes?

    What is the forward drop of those LEDs?

  9. Guest

    I've gone off the fading red eyes idea as it pulses continuously. All I
    want is for it to come on slowly when I switch it on and fade away when
    I switch it off. It is for a stage prop, goes in the top of an ornate

    I think the simple circuit across a cap is what I need, just gotta
    figure out the resistor combinations.

    Not sure what the drop over the LED is and what is a DMM?

    Thanks for the help, will play around with some resistor combos today
    and see how I go.

    I still want the fading red eyes for something else, but best get this
    one done first ;)

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