How to make LEDs go from constant light to flickering effect

Discussion in 'General Electronics Chat' started by Corbeau, Feb 2, 2013.

  1. Corbeau

    Thread Starter New Member

    Feb 2, 2013
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    Firstly, apologies for my ignorance on electonic matters (which will soon become apparent), I am very new to this and looking for some assistance.

    As part of a wider project, I currently need to create a circuit with 3 LEDs - this will most likely be 12v, and the LEDs likely to be no more than 30watts.

    At the press of a button or flick of a switch (or just a single action, rather than the manual twiddling of a rotary control...) need to be able to make these LEDs go from being on (in the normal, constant manner) to flickering - and not the candle effect flicker, but quite a notable on/off effect (but in a random/irregular fashion not binary). Similarly, a single button/switch needs to turn the constant light back on.

    There seem to be quite a few ways of getting the flickering effect in a fashion, but what would you recommend as a relatively straight-forward and safe manner? I'm open to any suggestion, whether some use of an oscillator, potentiometer or digital or whatever works (safely..)

    Many thanks (and thanks for your patience!) in advance
     
    Last edited: Feb 2, 2013
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Do you mean "flickering" in a random fashion or in a blinking manner? The latter is simple. A 555 circuit to make the LEDs blink, a DPST switch to select the 555 output or a constant input, and a driver circuit to power the LEDs. Sorry for the brief description but I am tapping this out on my phone.
     
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    "Flickering" can be done with two 555 oscillator circuits at different speeds and logically combining their output into one output that seems to be random.

    Bill Marsden has a great article on 555 oscillators; you can search for it on this forum.
     
  4. Corbeau

    Thread Starter New Member

    Feb 2, 2013
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    Thanks very much, it was the flickering in a random/irregular fashion rather than binary blinking. I'll have look at the article now.
     
  5. djsfantasi

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  6. Corbeau

    Thread Starter New Member

    Feb 2, 2013
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    How would you recommend changing the LEDs from being on to going to flickering - and back to on with a switch etc., can't quite see how to do that and that's the key to what I'm after? Again, utter ignorance showing and I've probably missed something blatant. Many thanks
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    For >30 Watts of LEDs, you'll want an LED Driver.

    Most LED Drivers have a PWM input for dimming.

    Solution:
    SPDT toggle switch (or your favorite type of switch)

    Put center pole to PWM input of LED Driver
    Put one end pole to continual +5V (or whatever voltage the LED Driver needs for PWM)
    Put other pole to output of the 555 flickering circuit.

    The power for the 555 circuit would need to be provided by another means, this is just an idea on how to switch between continual on and the effect using a simple switch. The upside of this approach (using an LED Constant Current Driver w/PWM) is that all the switching and effects can be done at low currents.
     
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