Total Newbie looking for a ton of help with Flickering LED Flames

Discussion in 'General Electronics Chat' started by pjveltri, Jan 15, 2012.

  1. pjveltri

    Thread Starter New Member

    Jan 15, 2012
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    Hi everybody,


    First of all I apologize if I posted in the wrong place.

    Secondly, I would greatly appreciate it if anyone could send me in the direction of books or the like to help me with my education in these sorts of things, starting from the super basics and going up to fairly advanced topics.

    Okay down to the meat of where I need some assistance. My little project has become more than I anticipated. I am looking to create flickering candle flames from 3 LEDs for a theatrical production. They would need to be fairly bright as they need to appear real from approximately 100' away all the way down to 15' away. I was experimenting with Arduino and with its hardware PWM outputs I was able to drive each LED to make it appear as one flame that had the appropriate movement. From there I am currently exploring how to make them controllable over the DMX lighting protocol or over 0-10v analog control, both which are currently above my level of understanding.

    For a small number of flames I would have no problem controlling them this way, however I need to create 100 separate flames in groups of 12 on 8 separate units. This means that I would have to purchase a minimum of 8 arduinos (but more likely 16 since I would want many of the LEDs to be flickering at different rates).

    Therefore, I am reaching out to the experts of this community to ask for lots of advice for what to do here, even if your advice is to send me to someone capable of designing the circuit I am willing to do that.

    All in all I would like the circuit to do the following.


    • Create a flame of 3 LEDs flickering at different rates to emulate a real candle flame.
    • be able to be "dimmed" in one way or another
    • Control the dimming by either DMX or 0-10v analog control.
      • Be able to address the unit if DMX control is used.
    • Be powered from a 120v 20amp AC circuit
    Thank You!
    PJ Veltri
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Try this link for several approaches... Flickering Lights You may have to go to the top of the page...
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    http://www.discovercircuits.com/dc-mag/Issue_nov10/pg-4.htm

    A similar ckt combines flicker with PWM dimming. Flickering effect is derived from a flickering LED, # G18571, THe Electronic Goldmine, US $ 1.19 or .70 ea lot of 100. I wonder if multiple flickering LED's having same pattern but different phase relationships would work? Using the inversion of U3 via U2 would give slightly different effect, especially if it was not next to U3's LED's. My LED candel uses one "bright" yellow LED from RS, not to happy with it; used a flame shaped envelope from 20W, miniture base 120V bulb.
    On Sgt. Wookie's PWM, would change clock to about 200Hz. Another PWM ckt is: http://forum.allaboutcircuits.com/showthread.php?t=49235, scroll down to Bill Marsden
     
    Last edited: Jan 16, 2012
  4. nerdegutta

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    Dec 15, 2009
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    @Bernard:

    First attachment. Isn't U4 an NPN transistor?
     
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  5. Wendy

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  6. Bernard

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    Cought-again- 2N3904 is still NPN; my excuse, recently I turn 85. Thanks.
     
    Last edited: Jan 16, 2012
  7. ErnieM

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    Each unit controls 12 LEDs. That's .24A with everyone on at the same time, which may be barely approachable with a single micro controller with no output buffers. However, just a simple transistor buffer is all you would need.

    As you already know you can PWM a LED to change it's brightness. This can be used for either a flicker or a dimming effect, and you can do both at the same time this way.

    DMX is similar to RS-232, it is actually RS-485which uses different voltage levels I believe. Driver chips to go from RS-485 to logic levels are available. The data that comes out is simple serial data the UART of any micro can handle. The exception is a start signal. If you already have the controller for this it may be simpler to use over the 10V analog, though that is also a good choice.

    To power from a 120v AC circuit just means you would have to add a small power supply, even a "wall wart" should do for the current you need. You should need no where near 20amps <grin>.

    Microchip has an application note on how to set up one of their chips for DMX. They wrote it in assembler but when I did something like this I used their free C compiler.

    I would call this a medium complexity project mostly due to this being your first project, so you have a bit of learning to do to get any micro you choose to work for you. I only suggest Microchip as that is the line I am most familiar with.
     
  8. pjveltri

    Thread Starter New Member

    Jan 15, 2012
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    Thanks everyone for your help, I am looking at all of your advice and will ask questions as I have them!

    PJ
     
  9. nerdegutta

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    Respect!

    Happy late birthday. 85 yrs! I wonder where I will be, in 45 years....:confused:
     
  10. bertus

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  11. pjveltri

    Thread Starter New Member

    Jan 15, 2012
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    Thank you all so much for your help.

    The PWM tutorial was invaluable in coming up with the dimming method for the LEDs. However, I went with a tutorial found here to create the flicker, as I was just not getting it and all of a sudden a due date was put on the project as my boss went out and just started buying parts without any form of final circuit.

    Below I will be posting my schematic as it currently stands, and I was hoping that if you see anything wrong with it that you could please tell me before I make a total fool of myself! Anyways, it will be running from a 12v battery and most resistors are currently a guess due to me not knowing what the specs on the LEDs he purchased are.

    [​IMG]

    Thank you all again for your help, I hope to continue to learn about all things circuity so I am sure this is not the last you will hear of me!

    PJ
     
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