# License Plate LED



## lenny (Jul 17, 2006)

Please help me all you LED Gurus.
I have a license plate holder on my motorcycle that uses a white LED
to illuminate the plate.
It came with 1/8" stub leads soldered directly to the power wires.
Needless to say, the leads broke off right at the LED base.
So, I need a new LED.
It's obviously a 12 V.
It's 7/16" dia at the base and about 1/2" tall.
Where can I get something like this?
Also, I'd like to get some sort of socket that the LED merely plugs into with the power source wires soldered directly to the socket.
It'll make changing them much easier. Plus, it'll probably be more rugged.
Please keep any comments simple as I really don't understand all of the LED jargon and wiring schematics.
Thanks all.
Lenny


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## rwolff (Jul 18, 2006)

> Also, I'd like to get some sort of socket that the LED merely plugs into with the power source wires soldered directly to the socket.
> It'll make changing them much easier. Plus, it'll probably be more rugged.
> Please keep any comments simple as I really don't understand all of the LED jargon and wiring schematics.
> Thanks all.



Why would you want to make changing LEDs easier? Even taking the 100,000 hour claimed lifetime with enough salt to rust the fenders off a Corvette, an LED bulb would outlast your motorcycle.

From an installer's perspective, the big difference between incandescent bulbs and LEDs is that LEDs are polarity sensitive. If you have a (for example) type 1156 incandescent bulb, it doesn't matter whether the shell of the base is grounded and the positive lead is connected to the tip, or vice versa. LEDs are polarity-sensitive. If you hook them up backwards, they won't light.

Since you don't understand the jargon and wiring schematics, your best bet is to get a "drop-in" LED replacement for a standard automotive bulb (LED assembiles with 1156 bases are available in red, amber, and white).

If you're going to go the "homebrew" route with 5mm LEDs, you should be looking at a multiple of 3 lights. Assuming you'll run them at 20mA, your power source is 13V (6 cell lead-acid is usually somewhat higher than the nominal 12V), and white LEDs typically have a voltage drop of about 3V. You could hook up a string of 3 in series with a 200 ohm resistor (180 and 220 are standard values, and should be close enough). If you look closely at the LEDs, you'll see that the "skirt" has one side ground flat. Hook up the negative supply to the "flat" side of LED 1, the non-flat side of LED 1 to the "flat" side of LED 2, the non-flat side of LED 2 to the "flat" side of LED 3, the non-flat side of LED 3 to one end of the resistor, and the other end of the resistor to the positive supply. Don't try a 4 LED "chain" with no resistor - the voltage/current graph of an LED is a bit wierd (trying to be non-technical), and you'd blow them out almost immediately.

When soldering to an LED, you need a heat sink (alligator clip, or pair of needle-nose pliers with a rubber band around the handles) clamped between the body of the LED and where you're soldering. Otherwise you'll risk overheating and damaging the LED.

From your description, it seems that the maker is throwing away one of the big benefits of LEDs - by having multiple LEDs (a single 5mm LED won't give enough light to meet the requirements for a license plate light), you can spread the lights out rather than having a single point source, for better illumination.

A final caution - automotive lights have certain legal requirements (e.g. brightness, and which colours are allowed to be seen from which directions). Some LED automotive products are not street legal (the package should say that they're for off-road or show use only). I'd hate to say it, but your best bet is probably to buy a stock plate holder with (incandescent) bulb - the manufacturer knows what's legal and what's not, and with aftermarket stuff you could be buying yourself a ticket.


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## chocho (Jul 18, 2006)

rwolff said:


> A final caution - automotive lights have certain legal requirements (e.g. brightness, and which colours are allowed to be seen from which directions). Some LED automotive products are not street legal (the package should say that they're for off-road or show use only). I'd hate to say it, but your best bet is probably to buy a stock plate holder with (incandescent) bulb - the manufacturer knows what's legal and what's not, and with aftermarket stuff you could be buying yourself a ticket.




I second that. I would definitely check online with your BMV or local law enforcement as to the requirements for (and against) lighting in the license plate area. Things that supply additional lighting such as neon plates are fine in certain states, but they'll get you a sure ticket in others.

For example - the law as it is stated in Texas:
http://www.txdps.state.tx.us/vi/Misc/faq/lighting.htm

Better safe than sorry.
-Chris


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