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Molex Power Mod.

Discussion in 'Modding' started by XG8, May 19, 2003.

  1. XG8

    XG8 Member

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  2. Cypher

    Cypher Member

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    [​IMG]
    [​IMG]
    [​IMG]

    *points at avatar*

    I did it first!
     
  3. OP
    OP
    XG8

    XG8 Member

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    Very nice... how did you get multiple colour in the last pic of yours?
     
  4. Cypher

    Cypher Member

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    Red + blue = pink...there are 2 LEDs in each molex connector, red and blue :)

    I've used 3mm LEDs rather than the 5mm ones used in the article. I didnt have to sand/file mine down, I just shoved them into the molex connector.
     
  5. SpeedyDerek

    SpeedyDerek Member

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    nice mod, wheres a cheapish place to get 5v LED's?
     
  6. SuperMarine

    SuperMarine Member

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    what about heat onto the power cables?

    no chance of them melting or something if they are constantly left on?
     
  7. -=ButFli=-

    -=ButFli=- Member

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    Since when did 3mm LEDs create enough heat to melt plastic?
     
  8. SuperMarine

    SuperMarine Member

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    i mean could there be a problem depending on the LEDS you use
     
  9. DDsD

    DDsD @DDsD

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    Not unless you were using super amazing brighter than anything imaginable LED's

    But even then i dont see any problems.. i mean.. whats a LED made of? Plastic ;)

    (yes yes i know... different plastics melt at different temperatures... but my point still stands :p)
     
  10. SpeedyDerek

    SpeedyDerek Member

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    my question still stands, where can i get suitable cheapish 3mm 5Volt LCD's?

    Dick Smith, Jaycar? Elsewhere? (melbourne S.E.)
     
  11. ChrisW67

    ChrisW67 Member

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    Any electronic component sales place will have suitable LEDs I would think. 3mm LEDs are common enough.

    The resistor varies depending on whether you use the 5 or 12V line to run them, and what the voltage drop across the LED is, and how much current you want to push.

    R = (Vsupply-Vled)/I

    Typical I is 10 to 20 mA (see LED spec sheets)
    Typical Vled is 1.2 to 3.5V (see LED spec sheets)
    Vsupply is 5 or 12V.
     
  12. Outlore

    Outlore Member

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    the problem is, 99% of LEDs run off 1.6volts(ish). you can buy ones that run off 12, or flash of 12v (like car alarm warning LEDs) but they have built in resistors to drop them down, and cost more than a LED + dropping resistor. you're best off finding the colour and brightness LED's you want, and then work out what resistor you need to drop them to atleast 1.6v...

    and yea, most LED's are 20mA
     
  13. Cnidus

    Cnidus Member

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    Outlore, check your PMs... (mini radiator ready and waiting for you)


    Also LEDs produce next to no heat atall, unlike light globes they dont use a white hot filament to glow.
     
  14. leboneez

    leboneez New Member

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    I've got a program here somewere

    for you to determine the nessasary resisters and even if you get a standard 5volt LEd it is recommended that you still use a resister.

    add me 2 msn and I'll send ya the proggy :D
     
  15. Jeffo

    Jeffo Member

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    i really want to do a mod like this but i don't understand all he different LED's and power sources and all other stuff like that...
    i was wondering if someone knew of a website that told me everything bout the power and stuff and also what i need for a mod like this..(eg drills, and other stuff)
     
  16. LethalCorpse

    LethalCorpse Member

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    You're going to wire it up like this:
    [​IMG]
    Ignore the dotted lines and the voltages - they're just to show you the voltage across the parts, not as part of the wiring. The led does have a polarity, the short leg is the cathode (negative) and the long leg is the anode (positive). You can also recognise it because the flat side on the body of the led is the same side as the cathode. In this diagram , you would connect one end of the resistor to the Red (5V) cable and the other end to the anode of the LED, with the cathode connected to one of the black cables (ground). Alternatively, you could wire the anode to 5V, the cathode to one end of the resistor and the other end of the resistor to ground. This is easy enough to do if you pull apart the molex plug using a pin or small screwdriver to push the flanges on the side of the pins down and pull them out slowly and solder the backs of the pins to the legs of the resistor and LED. You'll need to cut the legs fairly short (just dont forget which is the anode and which is the cathode), and you may need to use some electrical tape or heatshrink around the legs so they don't come into contact with each other. ow do you choose the resistor? In the diagram I've shown the voltages involved in the circuit. If you know the voltage drop across the led (I'll assume it's 1.6V, but it doesn't matter, so long as it's less than 5V) you can work everything else out. If the voltage across the led is Vled, then the voltage across the resistor is 5-Vled, in this case 3.4V. You now need to know what the current rating of the led is, we'll call it Iled and we'll assume it's 20mA, or 0.02A. Ignore the Led for now and just look at the resistor. There's 5V-Vled (or 3.4V) across it, and we want Iled through it, We use the formula V=IR to work it out. plug in the numbers, and you get 3.4=0.02*R, which when you calculate it, gives you 170, which means we need a 170 ohm resistor. You won't find one of these in the electronics store, but a 180ohm will do fine, and they're in abundant supply. If you can't find the exact resistor value, near enough is good enough. It's better to use a higher value resistor than a lower one, as a lower one will mean more current through the led and could blow it. So, putting it all together, the direct formula if you know Vled, Iled, and Vs (Vs means the source voltage, in our case 5V) to calculate the resistance you need is:
    R=(Vs-Vled)/Iled
     
    Last edited: May 20, 2003
  17. SpeedyDerek

    SpeedyDerek Member

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    so they're connected in series, and....

    Vs = Vr + Vled

    and (in our case)

    Vs = 5v
    Vr = ??
    Vled = 1.6v

    so, Vr = 3.4V

    Current in LED = 20mA

    I(led) = I(R) = I(Vs)

    V = I R

    3.4 = 20E-3 * R

    R = 3.4/20E-3

    R = 170 Ohms


    Does that look about right?


    Power = V I
    = 5 * 20E-3

    = 0.1W
     
    Last edited: May 20, 2003
  18. LethalCorpse

    LethalCorpse Member

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    yep, looks good. The overall power drain is bugger all, and the heat dissipation of the resistor isn't a concern - in this case it's 68mW, which isn't nearly enough to melt the plastic
     
  19. Nemesis

    Nemesis Member

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    ok so can you buy a 5volt led, and wire it straight onto the positive and negative 5v lines and it will work fine, and the molex will still have enough power?

    or do you NEED a resistor?

    :confused:
     
  20. LethalCorpse

    LethalCorpse Member

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    yes, a resistor rated at 5V can just be wired straight in. It'll either be a bloody bright led, or it'll have a resistor in series to drop it down. A 5V led will be much more expensive than a 1.6V led and resistor
     

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