LED voltage
Road Captain
Joined: Feb 2007
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From: East of Cincinnati Ohio
Elite HDF Member
Joined: Sep 2008
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From: Northwest
That means the LED will need 3.6v to operate. It will also mean it will 'drop' 3.6v across it. Yes, you will need a resistor to set the operating current. Most LEDs are rated at 20milliamps (.02ma).
To get 20ma at 13.6volts, you'll need close to a 680ohm resister capable of handling 1/2watt power dissipation.
You can put 3 of those LEDs in series with a single 680ohm resistor, operating from 13.6vdc.
I'm currently working on some custom turn signals, and my circuit has 5 LEDs in series because they are 2.1v.
To get 20ma at 13.6volts, you'll need close to a 680ohm resister capable of handling 1/2watt power dissipation.
You can put 3 of those LEDs in series with a single 680ohm resistor, operating from 13.6vdc.
I'm currently working on some custom turn signals, and my circuit has 5 LEDs in series because they are 2.1v.
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Cruiser
Joined: Feb 2006
Posts: 132
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From: NC
Archer, since you know a lot more than I do... My plan is to take apart my left rear directional, and install an LED on the bottom so it can't be seen. The LED will become my licence plate light that is mounted on my swingarm. I figure I can make it nice and clean without having to add any lights on the plate and deal with wiring on the swingarm.
Watt (punn intended) voltage LED would I need, and what resistors? Would the 3.2v be too bright? I want a nice dim to the plate, not a spotlght. But enough to display it.
I can wire crap, but resistors and LED's are new to me. Thanks..
Watt (punn intended) voltage LED would I need, and what resistors? Would the 3.2v be too bright? I want a nice dim to the plate, not a spotlght. But enough to display it.
I can wire crap, but resistors and LED's are new to me. Thanks..
yes... i make LED tail lights and turn sigs all the time... there are conversions online all over the place. the higher the resister the lower the power flow to the LED... they req very little power... on my brothers chop tail light i ran a resister to the running line i ran to that and then bridged the brake light switch to it... so it gets 1/4 power and acts as running lights normally then when he hits the brakes it gets full power... the radio shack guys should be able to help you... if not a google search will show the resister conversion tables
Elite HDF Member
Joined: Sep 2008
Posts: 4,440
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From: Northwest
Archer, since you know a lot more than I do... My plan is to take apart my left rear directional, and install an LED on the bottom so it can't be seen. The LED will become my licence plate light that is mounted on my swingarm. I figure I can make it nice and clean without having to add any lights on the plate and deal with wiring on the swingarm.
Watt (punn intended) voltage LED would I need, and what resistors? Would the 3.2v be too bright? I want a nice dim to the plate, not a spotlght. But enough to display it.
I can wire crap, but resistors and LED's are new to me. Thanks..
Watt (punn intended) voltage LED would I need, and what resistors? Would the 3.2v be too bright? I want a nice dim to the plate, not a spotlght. But enough to display it.
I can wire crap, but resistors and LED's are new to me. Thanks..
1. voltage, often labeled as 'forward voltage'.
2. luminosity, often labeled as 'mcd' (milli-candela) or 'lumens'
3. and current, most often rated at .020 amps.
To help you out, I would need to know those values from the datasheet of the LED.
First thing to look at when choosing an LED is it's light output ('mcd'/lumens) You'll probably want something between 1500 and 3000 mcd. Many various voltages, depending the material makup of the LED.
I'll leave it at that for now, till I know what you've got.
... and wiring the LED directly will quickly burn it out... they need current limiting of some type, to keep them from going over their max rated current.
Last edited by archergodwin; Mar 14, 2009 at 05:42 PM.
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