How would I go about doing this? (LED's)

Discussion in 'General Electronics Chat' started by Tom,, Apr 19, 2010.

  1. Tom,

    Thread Starter New Member

    Apr 19, 2010
    5
    0
    Hello,

    I'm new here so here's my first post.

    How would I go about connecting 50 orange LED's up and a small computer fan all into one circuit. I need to get something like this built up as I'm doing it for a friend who is a beaver leader and needs it to put under a bamboo frame with orange cellophane around to make an "indoor campfire". I would also like to know if there was any way to make it flicker or control the brightness with a device or a laptop?

    What would I need (power supplies, resisters) I would prefer it to be batteries due to the nature of use however if a mains supply would be better then I'm happy with that.

    Thanks,
    Tom

    P.S (Needs to be done by two weeks on friday)
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Computer fans are 12V DC. I guess your idea is to use the fan to make the cellophane whip around.

    LEDs need DC power.

    Do you have the LEDs on hand already? If so, what are their specifications?

    Have you built any electronics projects before? If not, it's a somewhat ambitious 1st-time project, and you don't have a lot of time to get it working.

    A 12v sealed lead-acid battery would last quite a long time. It would be a lot cheaper to just use a power adapter though.
     
  3. Tom,

    Thread Starter New Member

    Apr 19, 2010
    5
    0
    Hello,

    Thank you for you're reply.

    I've bought some LED's already. They have a forwards voltage of 2.4 (2 min, 2.8 max).

    I haven't done any electrical projects before however, I use to do quite a lot of work for BT in my old days so I know how certain things work etc. I just need to know what type resisters I would need and everything else to work.

    Regarding battery's or power supplies. It would depend on how long a battery would last. I was looking at a 12v battery from here. I don't know which one would be best so any recommendation would be helpful.

    So as a list, what would I need. I have put below what I currently have. As I said I would prefer a battery as it would need at least a 50m power extension to reach.

    This is what I currently have.

    50 x 5mm LED's (2.4v)
    12v PC Fan

    What else.

    Regards,
    Tom
     
    Last edited: Apr 19, 2010
  4. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    This might be useful:
    http://led.linear1.org/led.wiz
    Unless you can test them assume they have the minimum forward voltage, and make sure they get good airflow because otherwise they are going to get hot and die.
     
  5. Tom,

    Thread Starter New Member

    Apr 19, 2010
    5
    0
    I might change the idea and instead of using led's get some Orange light bulbs and make them flicker.

    Anyone know how to make GU10 bulbs flicker?
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Silk works much better than cellophane for mock flames.
    I used to make these for stage effects. You weight the top of the silk slightly so it continually falls and perks back up.
    I used yellow leds on one side and orange and red on the other.

    Mount the flame material to the cross members in front of the fan, and glue the LEDs to the circumference of the fan, facing the flame material at random angles.

    The problem with the cellophane is it reflects the bright DOTS of the leds. The silk (fake silk) diffuses the light giving you a realistic look.

    Use a pot to vary the speed of the fan. too fast and it wont look real. (unless you weight the tops more)
     
  7. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    12V 7Ah looks good, should give 11 operating hours. What is current draw of LEDs?[ 20 mA ?]. Do you have access to electronic parts? Can you use a socket strip to make blinker? Will give schematic if you wish to try. Made a short experiment with fan & faux silk, gives a "fire" 12 cm dia.
     
  8. John P

    AAC Fanatic!

    Oct 14, 2008
    1,634
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    Model railroaders have a trick for making a "flickering fire". You get a small orange light bulb and an old radio. Then you remove the speaker from the radio and connect up the bulb to the terminals that drove the speaker, then tune the radio to a talk station. The sound appears as random fluctuations in the bulb's brightness. I imagine it would be even better if you had multiple light bulbs and multiple radios all on different stations! But that's for a tiny little fire, like a hobo camp or something. If you're talking about a simulated full-size fire that has 50 LEDs, that's maybe another thing altogether.

    Or, a microcontroller set up to produce a psudo-random pattern, or multiple patterns for different outputs. It could repeat every few minutes and nobody would notice. But to do that you'd need some specialized skills.
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Have you read this?

    LEDs, 555s, Flashers, and Light Chasers

    Chapters 1 and 2 go through the basics of LEDs.

    I would add a couple of yellow and red LEDs, very few fires (camp fires especially) are moncromatic.

    I'm working on a sound modulator for LEDs that might be modified for your use. I'll post it tomorrow.
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    OK, I finished some schematics I've been working on. I've never built these yet (I will), they are for the rewrite on the article I pointed to earlier. It may be more than you wanted to do, but if you need help we'll get you there.

    Basically it is the same idea as John P had, you use a simple transistor radio to make them flicker.

    There can be spare op amps and comparators that can be used to make more than one modulator.

    [​IMG]

    Parts List
    U2 - 555 IC
    U3 - LM393 Dual Comparitor (can be a quad with modification)
    U4 - LM358 Dual Op Amp

    Example B has more adjustment range in the form of R11, basically it is an internal volume control. I haven't decided which version I'm going to use for my article, that is a subject for another thread. I'll probably modify it a bit before I'm done.

    The link to the rewrite is here...

    LEDs, 555s, Flashers, and Light Chasers

    Look up Chapter 12.
     
    Last edited: Apr 22, 2010
  11. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    My last thought on this post.
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    You know, it might be easier to use a constant current source like this and feed a signal from an AM radio to it.

    [​IMG]
     
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