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Need help connecting leds to molex

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goodgod

Member
Joined
Feb 18, 2006
Title says all, I want to connect 5 red LEDs to a molex connector, to light up my acrylic window, like the guy did with some mousepads at this link:

Lights and acrylic

It has to be simple, but I have no knowledge at all with volatges, amps, resistance, etc... I just want to plug the LEDs to a male 4pin molex connector. I got a soldering iron and the molex connector, so now I just need to know what to do with these.

Thanks. :)
 
assuming they are regular leds not blue or hyperbright they will be 2.2v @ 22ma.
You can easily connect 5 leds in a serise for a forward drop voltage of 11v.
Then with ohms law you can calculate the vdrop resistor to compensate for the difference. In this case running all five in a serise off the 12v line shouldent hurt them but you're better off follwing the procedure im about to explain.

The formula is R=E/I where R= resistance , E= voltage, and I = current in amps.
22ma is equal to .022Amps and your voltage differance is 1v (12v-11v).
Plugging this into the formula you get
1/.022=45.45
so a 50 Ohm resistor would be fine.
A 50 Ohm resistors colour code is Black, Green, Brown.
Also note that the longer lead of the LED is the positive connector.
 
ok... so now how do I place the LEDs connected to the molex....do I use the black and red wires? In what order do I solder all the stuff?
 
If you are doing what skeith said, you would wire them all up in series. The LEDs have two legs, one longer than the other, the longer one being positive. You would connect all of the leds so that the longer leg connects to the shorter leg of the other, then you would stick the resistor in between the shorter leg of the last led and the black ground wire, and the longer leg of the first LED to the yellow 12v wire.

I uploaded a picture if that makes sense.
 

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Ehh, it doesn't matter if you put the resistor before or after the series of diodes. You can put them between the longer leg and 12v or shorter leg and ground.
 
ok, would that work if I use LEDs that require more than 12v all together (like superbright ones or w/e)
 
goodgod said:
ok, would that work if I use LEDs that require more than 12v all together (like superbright ones or w/e)

no, you would do the same idea, but break them up into strings of LEDS adding up to 12v, and then just make groups of those.
 
ok....that means I can put for example 3 superbright LEDs together on a lead with a resistance, using the black and yellow wires on a molex connector, and do another setup like this for the other two other LEDs, using another molex connector, or maybe the red wire (5v?) if this is enough

I don't understand how it works because if I split the power in two connectors, then plug these two connectors into one with a splitter, it would work...maybe not.

Could I do something like that?

connector6xg.jpg
 
Your wiring is in parallel, you need to do it in series, I did a crude editing of your picture to show what a series connection is. The simplest example of the idea is the batteries in a gameboy, they are connected positive to negative in series with 4 batteries, and have a voltage rise of 4 x 1.5v. Here we have the opposite, we have N x (voltage of led), where n is the number of LEDs. We want this to equal a drop of 12v.

You might want to get a intro book on physics or electronics from the library, all you really need to understand is OHMs law and you should understand how to wire this up. Google, wikipedia, or howstuffworks.com might be good as well.

Let us know what LEDs you are using.
 

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I'm going to buy the LEDs tommorow, I'm looking for super bright ones. I'll tell you then what are the specs of the LEDs.

What I need to know is what to do if I got 5 LEDs to plug into a connector and that 4 of them equal 12v (for example). Can I just use another LED on another molex connector?
 
i ordered 5 super bright red LEDs, 5000mcd, here are their specs

* Source Material:InGaN
* Emitting color:Red
* Lens Type:Water Clear
* Luminous Intensity-MCD:4000 Typical/5000 Max
* Reverse Voltage: 2.7 V
* DC Forward Voltage:2.0V Typical
* DC Forward Current:20mA
* Viewing Angle:15 Degrees
* Lead Soldering Temp:260o C for 5 seconds

The voltage is the foward or reverse one? If it's the foward, using your ohm rule, i would need a 51 ohms resistance right?
 
ok so your voltages are abit lower than the standard leds. With these leds you should be able to connect all of them in serise on the 12v rail with a 100 Ohm resistor. The leds have a 2v forward drop @ 20ma.

R=E/I
R=12-(2*5)/.020
R=100 Ohms
 
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