L.E.D license plate problem.. need help!
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Member
Joined: Sep 2006
Posts: 166
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From: Mahwah,NJ
2005 C55 ////AMG
L.E.D license plate problem.. need help!
hey guys,
Ibought a pair of l.e.d's for my license plate lights. the problem is they blink on and off when inserted...i tried alot of things but no luck..anyone know or has done this ? wut resistor should i use or what..NEED HELP?????? thanks
Ibought a pair of l.e.d's for my license plate lights. the problem is they blink on and off when inserted...i tried alot of things but no luck..anyone know or has done this ? wut resistor should i use or what..NEED HELP?????? thanks
Super Member
Joined: Jan 2004
Posts: 538
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From: Silicon valley
Audi C7.5 S6
LEDs should be driven by a current source, not a voltage source, which would be the reason for adding a resistor. The resistor value would be chosen based on the current requirement of the LED and the voltage drop of the LED. Assume a nominal battery voltage of around 13.2V.
Also, one should know how much current current the stock bulbs require and how much current the LEDs require, before plugging in an LED.
Also, one should know how much current current the stock bulbs require and how much current the LEDs require, before plugging in an LED.
Super Member
Joined: Jan 2004
Posts: 538
Likes: 2
From: Silicon valley
Audi C7.5 S6
Also, if they are blinking on off, because they are drawing too much current, then use a a very low current relay (with reverse diode accross the coil, to kill the inductive kickback) to isolate the load from the MB driver circuit.
Some current limiting circuits will pulse on/off, if overloaded, which means it is being overstressed.
Some current limiting circuits will pulse on/off, if overloaded, which means it is being overstressed.
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MBWorld Fanatic!
Joined: Jan 2005
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From: Orange County
2005 C Wagon (No snickering please!)
LEDs should be driven by a current source, not a voltage source, which would be the reason for adding a resistor. The resistor value would be chosen based on the current requirement of the LED and the voltage drop of the LED. Assume a nominal battery voltage of around 13.2V.
Also, one should know how much current current the stock bulbs require and how much current the LEDs require, before plugging in an LED.
Also, one should know how much current current the stock bulbs require and how much current the LEDs require, before plugging in an LED.
Here is a link for a resistor that can be mounted to the car frame to eliminate the heat.
http://www.newark.com/jsp/search/pro...sp?sku=65K1854
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Super Member
Joined: Jan 2004
Posts: 538
Likes: 2
From: Silicon valley
Audi C7.5 S6
The value resistor to use will depend on the particular LED you have. Forward voltage drop can be anywhere from 1.7V to 3.5V, depending on the kind of LED. Typical current draw, for a small LED is about 20mA, but there are some new ones that draw 300mA or more.
The voltage drop, depends on the materials and doping used for the LED semiconductor, since it depends on the band gap voltages. Infrared and red (1.6-2.1v) have the lowest voltage, ultraviolet and blue have the highest voltage (3-3.5V).
There is no universal resistor size for an LED.
The voltage drop, depends on the materials and doping used for the LED semiconductor, since it depends on the band gap voltages. Infrared and red (1.6-2.1v) have the lowest voltage, ultraviolet and blue have the highest voltage (3-3.5V).
There is no universal resistor size for an LED.
