Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Wiring LED's



Wiring LED's | 8 October, 2003

I need to wire some LED's. I have a pair installed in my headlights that use some sort of small thing at the end of the wire. They run off of the 12 volt car battery. They can stay on for over a month without starting the car and still not drain the battery. I recieved a device that has 12 small LCDs on it. I wanted to detach them and wire them into my car at various places. Do I need some sort of resistor, restrictor, etc? I have no idea what that little piece it at the end. I do know they only work if wired a certain way. They do not work backwards.

Thanks, Clint

This message was posted Add this forum to your site! Click to learn more. the Electronics Forum @

reply »


Wiring LED's | 9 October, 2003

Look here:

If you don't know the current, experiment with different values of resistor. Starting with the highest value resistor that doesn't dim the light too much then lowering it as needed.

Connect the anode and cathode terminals of the LED correctly or it will not light. 50:50 chance, eh?

reply »

Ming Diaz


Wiring LED's | 20 October, 2003

Hombre, presuming you are doing this as enhancement for looks, I have some comments.

1. LED's seldom run on more than 3 volts. 4.5 volts max for some special types. Because the car is 12 volts all over, you have to use a resistor to reduce the voltage to the LED. Failure to do this and pop goes the LED! 2. Not knowing the exact type of LED you are using, I suggest you (or someone you know who is savvy about basic electricity) do an experiement with one LED and a variable resistor, say zero to 3000 ohms. Wire the LED in series with the variable resistor, crank up the var. res. to max, then hook up to the car battery and SLOWLY turn the var. res. down until you get a glow on the LED. If you reduce the var. res. too much, blooie, you loose one LED, no big deal. Once you find the setting on the var. res. that gives you a nice glow without making the LED warm, disconnet the battery, read the var. res. with an meter to find out the value of resistance (I bet it will be around 500 ohms. You goto the local radio shack, get some of that sized resistors, wire (solder it for long life) it to the LED and you can place it wherever on the car. 3. Yes, LED's are diodes and only work one way. Nature of the thang. 4. LED's use very little juice, so you can leave them on for a very, very long time on the amount of power available from a car battery. Like pushing a tonka toy with a D6 bulldozer. Personal warning: If you are goofing around with LED brake lights (you can find them at the junk yard all the time) and come across an array with one long, thin light tube inside, this is a neon array and it runs on a much higher voltage. Be aware that it will give you a zap if you don't handle with care when it's active. Hope this helps.

This message was posted Add this forum to your site! Click to learn more. the Electronics Forum @

reply »



Wiring LED's | 27 October, 2003

A light emitting diode or "LED" doesn't care about voltage, it will light with approx. 10 to 20 milliamps of current. In a 12V system (such as an auto), a resistor of 1K ohms is ideal. At 12V, this allows about 12 mA of current, at 13.8V (approximate alternator output), the current would be about 14 mA. Yes it is a diode, so has to be forward biased to light. The current limiting resistor can go on the cathode or anode, it'll do it's job either way.


reply »



Wiring LED's | 30 October, 2003

I have about 9 Super Bright LED's in my car. I use a 560 ohm Resistor 1/2 watt soldered in-line to the longer lead of the LED. Works fine.

reply »

Capillary Underfill process

Rework Training Materials