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Thread: LED/Resistor ?

  1. #1
    Member dtrunk's Avatar
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    LED/Resistor ?

    gonna do some mod'n n need some help.

    http://www.ebay.com/itm/300697205097?#ht_2451wt_961

    volt ~1.8-2.1
    miliamps <30

    i want to connect 6 of these to one resistor as shown(on the right); as these came with 510ohm resistors. Of course i can buy a pack of 270ohm, but if I can wire this as I imagine, it'd save me $5. though I understand I could blow a couple LEDs playing around.

    The image is from ledguru, and calculates 3 leds in series at 12v supply, 2v for led at roughly 22mAmps with a 270ohm resistor. I want to modify that as the image on the right shows, use the supplied 510ohm resistors and wire 2 sets of 3 leds in series. essentially using a 255ohm opposed to 270ohm, which will up the mAmps a little. Does this work? if this sorta math works, opens the door for lots of fun.

    Edit: doh, meant to post this under the alt mod forum. some1 pls put this where it belongs; if not here.
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    Last edited by dtrunk; 05-08-12 at 12:11 AM.
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  2. #2
    Member jazon1's Avatar
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    its been awhile since ive done any real electronics work but did go to school for it,and could be wrong but couldn't you just run all 6 in parallel and get 2v per led from your 12v source with no resistor?
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  3. #3
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    Last I checked, LEDs required 3V. And yes, the path of least resistance (pun intended) is to just use 4 LEDs in series for a 12V source*. If you want to use resistors instead, I'd suggest two 240 ohm resistors, one for each series array, with the 2 arrays in parallel.

    *Put heat shrink over the 4th LED if you don't want to see it. Yup, that's right, hillbilly electronics...
    Last edited by hafa; 05-08-12 at 04:49 AM.
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  4. #4
    Member dtrunk's Avatar
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    LED Guru pretty much always suggest a resistor, and this was one of the things confusing to me. Even if i setup 6 LED at roughly 2v, it splits the chain of 6 in to 2 chains and suggest a resistor for both chains. So, I sort of assumed a resistor in the path would be helpful regardless. but, my degree is in business, not electronics, and so I ask you guys.

    @hafa; as far as i can tell, these are 1.8-2.1v. i will try daisy chaining 5 of them, mayb 6, and see how it looks. I'd just really prefer not to blow any. thanks for the replies guys.
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  5. #5
    Underwater Senior Member
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    Yes, you can daisy chain 6 of them and they should light. (there are 2V LED's too)
    A resistor isn't a bad idea, but the way you have the 510 Ohm one pictured isn't correct. You would still use one of the same 270 Ohm resistor the way you have it diagrammed, but of an increased wattage value (if needed), for 6 it's just right. Move to a half watt resistor for adding more legs of 3
    Last edited by Diggrr; 05-08-12 at 12:51 PM.

  6. #6
    Member dtrunk's Avatar
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    whoa, crazy info diggrr. thanks. so if i am reading this right, with three in series, and a call for a 270ohm resistor, i could run multiple chains of 3 off of one resistor?

    so in that case, can I use the 510ohm supplied to run one LED from 12v, and run multiple LEDs of of that one resistor?

    so it would b 12v power ---> 510ohm ---> LEDs + (but the LED would b 8-12 of them, depending on how many I use per fan, and I'd take the HOT from the resistor, chain that to a HOT lead that hits all LED +, then also chain LED - in to one line.) so can I run 8-12 of these in parallel of of one 510ohm resistor??
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  7. #7
    Member dtrunk's Avatar
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    like this dig, but with 8-12 LED in place of the 4? does that work?
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    CPU: Intel i5 3570k @ 4.0ghz 1.17v
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  8. #8
    Underwater Senior Member
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    I think that the 510 resistors are to run a single LED from 12 volts.
    Since the resistor is 1/4 watt, (guessing, you didn't say) then you can hook up a maximum of 6 LED's to that one resistor, and have their other legs tied to the negative line like you diagrammed.

  9. #9
    Underwater Senior Member
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    BTW, you can get those LED's for $2 for a 100 at MPJA.com

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