Question about LED wiring people do...

Discussion in 'Creative General Discussion' started by jaraxel, Feb 12, 2012.

  1. jaraxel

    jaraxel Well-Known Member

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    Hi all,

    So here I am, on my first custom (as in, ever :)  ) and stupidly decided to tackle movie (jetwing) leader OP...

    So while I did a LED swap (I changed it to white led since I like it more white and the blue tint from the light pipe is enough), it still lights up using the original factory wiring.

    For those of you who are experienced in these things, how do you do the rewiring? do you take the entire thing apart, rip out the sounds, and install a LED switch in the speaker/logic board area? I didn't take the body apart, but really curiou show you guys do it.
     
  2. frenzyrumble

    frenzyrumble Banned

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    just change the LED, nothing else. you'll need wire cutters, solder, soldering gun, some tape. that's it.
     
  3. jaraxel

    jaraxel Well-Known Member

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    Thanks for reply. That's what I did (change the led) but since the electronics are still the original, it'd only flash instead of staying on. So I'm wondering do folks actually rip out the electronics in the chest or install a separate switch to kee the led (esp in the head) on?
     
  4. frenzyrumble

    frenzyrumble Banned

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    ah, that's a whole different task. You can run wiring straight to the power source/switch/etc, bypassing/eliminating the chip which is causing it to flash. I think that's the easiest way. curious, are you are trying to have the light on/off with it's own switch, or ; light up when it normally does, but not blink?
     
  5. jaraxel

    jaraxel Well-Known Member

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    Originally I was thinking of preserving current behaviour and add an on off switch (and not blink), but I'm sure that's uch more difficult than just rippig out the sound, etc.

    Biggest problem is I'm actually 70% done with the repainting and don't think I have the guts to redo it all... so trying to figure out what I can do, if anythig, at this point..
     
  6. MegaMoonMan

    MegaMoonMan OFFICIAL MMM REP

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    You can keep the original behavior AND add a switch to make it stay on fairly easily. All you need to do is run another wire to the + side of the LED to the + side of the battery with a switch in between (assuming the LED ground is always grounded). If the ground is switched off you'll just need to run another wire between the negatives.

    Depending on the battery and LED voltages you may have to add a resistor into one of the wires (to keep it from burning out).

    EDIT: You don't even need to run more wires all the way to the LED, you just need to splice the new wires into the originals wherever convenient.
     
    Last edited: Feb 13, 2012
  7. frenzyrumble

    frenzyrumble Banned

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    right. you could theoretically just solder 1 end of the wire directly to the power source of the figure (what is it? 2 or 4 AAs?) then wire to the other end (preferably +) , intercepted by an on/off switch. I've ran 3mm LEDs to a pair of AAs and they've lit up nicely. I would test here too though, if too bright, you'll need to add a light resistor in the line.
     
  8. jaraxel

    jaraxel Well-Known Member

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    aah... thanks for the advice, let me take a look how to take it apart without destroying the paint job....

    It's actually 2AAs :) 
     
  9. MegaMoonMan

    MegaMoonMan OFFICIAL MMM REP

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    I believe a white LED can take 3 volts with no resistor.
     
  10. jaraxel

    jaraxel Well-Known Member

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    It does seem to heat up after holding it up to the batteries after a while, how do I know if it needs a resister? Oh great... my physics class from waaaaaaay back and the colour banding is coming back..
     
  11. MegaMoonMan

    MegaMoonMan OFFICIAL MMM REP

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    You need to know the specs of the LED. I remember reading somewhere that a white LED usually uses 3 - 3.3 volts, so 3 volts should be fine. That is in no way a guarantee.

    You should probably put a small one on it just to be safe.
     
    Last edited: Feb 14, 2012
  12. big hank

    big hank Resident Slacker-Basher

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    I can recommend a 470ohm 510ohm resistor as a good all purpose "default" for transformers projects.
     
  13. Shwiggie

    Shwiggie Likeable dryskinned biped

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    An LED has a stated current rating for maximum safe brightness. The less current, the less brightness, but the life of the LED is extended. You do this by using a limiting resistor in series with the LED...this means you hook a wire from the + terminal of the battery to the resistor, a wire from the other side of the resistor to the long lead from the LED, (the order in which you hook up the resistor and LED doesn't matter) and another wire from the LED's short lead to the - terminal of the battery.

    We're talking Ohm's law here: Voltage (V) = Current (I) times Resistance (R). White LEDs typically take around 3 volts to bias and around 20mA (0.02A) of current to drive (the package should tell you exactly). Since diodes usually have a voltage drop 0.7V, you wind up dividing 2.3V by 20mA to get find using Ohm's law that your limiting resistor should be around 115 ohms.

    If you don't find one that matches that figure (probably not), go the next size higher to keep your current below that optimum forward current. With the loose tolerances of most electronics you don't have to be especially precise...it's not like you're building a piano here. For that matter, calculating the voltage drop isn't that important unless you're dealing with multiple series-wired LEDs.

    And if you don't like calculations, look for a potentiometer (variable resistor). You can vary LED brightness with them without getting too technical. Just remember that it's there to limit the current, so get a pot that's larger than that calculated value...you'd probably want a 100 ohm resistor in-line with it to prevent a negligent burn-out.

    And, by all means, use a battery holder. They have them at Radio Shack for 2 AAs if you don't want to make one. PLEASE don't solder directly to a battery. I know it was mentioned "theoretically", but it's a bitch to do without messing something up realistically.
     
  14. frenzyrumble

    frenzyrumble Banned

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    yeah, I learned the hard way it's impossible to solder to a battery...
     
  15. jaraxel

    jaraxel Well-Known Member

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    Thanks for the detailed explanation and tips guys!

    Let me see how to take L OP's torso apart without seriously damaging the existing paintjob.. unless I buy a small rotating saw and cut open his battery compartment... hmmmmm
     

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