http://www.sporttruckdirect.com

 

LEDs draw MORE amperage when you start adding resistors. You can dim a LED, but it takes MORE amperage to power it. If you install LEDS, and add resistors, add a variable resistor (pot) and use a dedicated line for it. I would not suggest adding LEDs to a dash light circuit. A 15 volt LED, per say is designed to run @ vehicle voltage. When you toss in a resistor, now the LED has to draw HIGHER current to illuminate the LED.


A resistor drops voltage.

You would want a variable resistor that can handle 2 watts of power. Doesn't sound like much but add a bunch to your electrical system on an exsisting circuit, and you will have problems.

Just my 2 cents.


Good luck.

 

hate to do this but...

resistors Limit current, not cause it to draw more. if you have a 12V system and a circuit that draws 1 amp w/o a resistor, adding one inline will cut the current and change the voltage drop across the device... ohms law... v = i * r. i = v / r etc... v= voltage, i = current, r= resistance.

if one were to swap out the lamps for led's the total power for that circuit would drop. led's are going to draw less current than a lamp.

 

Thanks for the catch, I thought I posted it but then again I'm a dumbass

 

I don't wanna argue either.....


A resistor limits current via a voltage drop.......... and that's all I'm gonna say.


All I know is that when I added my 4 gauges to my headlamp switch, it fizzed out quite quickly. Autometer said that adding a 10,000 ohm variable resistor for each gauge will be needed to dim 2 LEDs per gauge. The 2 LEDs at 14.4 volts, draw 1/4 watt, combined. My variable resistors are 10,000 ohm, 2 full watts each. When I dim the gauges down, the pots get slightly warm. Not blistering.

The LEDs are getting a lower voltage, BUT require a higher amperage to jump the gap in the bulb.

My resistors in the truck drop the voltage, but still allow higher current levels to pass through.

It takes more power to dim an LED.


That's my understanding, and I'm sticking with it.....lol.

No disrespect.


Take care....

DD

 

I didn't think leds dim. I thought they cam on at a certain voltage and went out when the voltage dropped below that voltage. I'm pretty sure it is this way because I have an led flashlight, it does not go dim when the battery goes dead. It just quites shining.

 

Come on now ... E=IR.

If the LED's are getting a lower voltage ... then they DRAW fewer amps. Ain't nothing pushing those little electrons through the resistance except the voltage applied. Half the E = half the I. [8D]

jakebrake: I'm with you ... I thought LED's produced a constant output ... until their bias dropped below threshold ... then they just go out. But if folks here are experiencing something else, I'll have to look again. Oh, and be careful ...

... if Tani sees that ^^^^ he'll never let you forget it.

 

Ok, so, if I want to replace some of my interior lights with led's, then I should just hook them up without a resistor to avoid problems if I don't mind the brightness?

Like, say I decided I wanted to replace the bulb in my glove compartment with a few led's, couldn't I just simply buy a few from radioshack and then wire them up?

I've dealt with electrical in the past, but it was all basic simple robotics stuff like wiring up motors and pneumatics...

 

LED's need only 0.7 volts of forward bias to turn on, the higher the voltage, the more current that will pass thru a diode. add a resistor and now your limiting the current that can pass thru the diode by (Vmax - 0.7)/R

so if you have a 12 volt system and a 470 ohm resistor in line with the led... (12v - 0.7v)/470 = 24ma of current thru the circuit. lower the resistor value and the illumination goes up with more current passing thru the diode. if you have no resistor than the diode will flow the max amount of current that it can. they dont last too long that way.

here, read this... it should help.
http://electronics.howstuffworks.com/led.htm

edit: oh yeah, there are multiple pages that are kind easy to miss... find the next button in the middle towards the bottom of the page...

 

Same light $100 less on ebay. Anyone have these??