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i<3 my P.O.S.
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Discussion Starter · #1 · (Edited)
trying to change the window switch LED to blue
how should i start it off ??? do i just take out the old LED and put new one in ???
top of a 2004 accord coupe passanger side window switch

bottom

don't know what i should do i got the LED already from ebay and it came with 12v resistor (i think) ........what should i do ?????very confuse
 

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Well the LED should already be protected with a resistor in that window switch. I do see a resistor very close to the LED mounts. I modded a few leds with different ones and all I did is use a solder(pin) iron and remove the LED from the circuit board, cut the new LED wires to length, and then solder them in place of the old LED.

All LEDs need a resistor so you do not burn them out...LEDs can not handle alof of current. The LED you got on ebay can still be used, I would just remove the resistor (or just not use it). The LED from ebay is most likely a universal application where you can hook it up to 12V and they provide a resistor so its protected.

Hopfully others will chime in and give their experiences with this window switch mod.
 

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i<3 my P.O.S.
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Discussion Starter · #3 ·
yeah there blue LED so i don't know if there different or anythingi tried it with the factory resistor but it doesn't even light up
 

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04accordcoupe said:
yeah there blue LED so i don't know if there different or anythingi tried it with the factory resistor but it doesn't even light up
Make sure that you installed the LED the correct way. If you look at the LED there is a metal wire/line inside the bulb. one side is the + and the other side is the -

If you put it in backwards it will not work.
 

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We also tried this same experiment, and made sure both anode + and cathode - were correctly wired, but did not light up. What is the deal?
 

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Discussion Starter · #6 ·
yeah and i thought i was messing it up in someway tried it both way change out the resistor for a 12v one too and it still won't light up....we need some LED experts in here...i am using 3mm LED bulb don't know if i should try 5mm if it does any difference
 

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You need to buy the regular LEDs without any internal resistance. These operate at around 0.7volts and should work. Like the guy said before, the circuit must already have a resistance in series with the LED so additional resistance built into the LED will cause too little current to flow and it wont light up.
 

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mog said:
You need to buy the regular LEDs without any internal resistance.
So um, how exactly does that work? If there is a voltage drop, then there is an associated resistance.

Also, it will probably be insanely difficult to find an LED with that low of a voltage drop.

I think the problem you guys are having is that LEDs are very sensitive to the amount of voltage applied to it. If the applied voltage isnt high enough for that particular LED, it just won't light up.

Also, the resistance of an LED does not have a lienar relationship with current. Thus, if you are using an LED with too high of a resistance, this may have a significant effect on the current running through it, which would explain why it doesn't seem to work.

IMHO, your best bet is to find the exact specs of the OE LED using a multimeter a, a battery, and a variable resistor (1Kohm would do fine, you can find these for a buck or two from Radio Shack). From there, you can buy the appropriate LED.
 

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sumptimwong said:
So um, how exactly does that work? If there is a voltage drop, then there is an associated resistance.

Also, it will probably be insanely difficult to find an LED with that low of a voltage drop.

I think the problem you guys are having is that LEDs are very sensitive to the amount of voltage applied to it. If the applied voltage isnt high enough for that particular LED, it just won't light up.

Also, the resistance of an LED does not have a lienar relationship with current. Thus, if you are using an LED with too high of a resistance, this may have a significant effect on the current running through it, which would explain why it doesn't seem to work.

IMHO, your best bet is to find the exact specs of the OE LED using a multimeter a, a battery, and a variable resistor (1Kohm would do fine, you can find these for a buck or two from Radio Shack). From there, you can buy the appropriate LED.
Actually most LED have voltage drop of 1.6V. This is a forward voltage you need to apply to allow conduction of current and thus emitting the light emission. There's tons of LED info online
:D
 

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Really? I haven't built any LED circuits myself, but my impression was that the voltage drop across resistors should be on the order of 3.0 volts.
 

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It varies. There are several parameters in a simple LED circuit

V_supply=DC power supply
V_forward=forward voltage drop of LED(this value is extracted from LED datasheet)
I_Led= desired current flowing through LED(typically you want 15mA~20mA so u dont burn it out)
R=current limiting resistor

Using nodal analysis of the series circuit you arrive to this design equation:

(V_supply - V_forward) / R = I_Led

V_supply is a value you choose based on your application say V_supply=12V
V_forward is from the spec sheet of the LED. Say V_forward=3V
And we set I_Led=15mA.

And you just solve for R

Some LED have "built in" resistor R so you dont need to add external current limiting yourself. They design the R for you to work at the specified supply voltage.
 

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^ hahah thanks, but I think you've forgotten to take one thing into account. I believe there is some resistance from the LED itself, which you should not neglect. R should really be (R_external + R_LED)

So you're still saying that a typical appropriate deltaV for an LED should be 1.6V, even though you're using 3.0V in your example?
 

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Yea that's true. You can model the internal resistance of the LED but that parasitic resistance is very small and doesnt play in part in design the current limiting resistor.

I just looked up a Mouser catalog and seems like Vfoward for LED typically range from 1.5~3V.
 

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Discussion Starter · #15 · (Edited)
ummm english please i was tottaly lost back there....
anyways i bought these off of ebay and they are blue LED there 3mm and there 5000MCD(whatever that is) and they come with seperate resistor that i can soder on to make them 12V
 

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04accordcoupe said:
ummm english please i was tottaly lost back there....
anyways i bought these off of ebay and they are blue LED there 3mm and there 5000MCD(whatever that is) and they come with seperate resistor that i can soder on to make them 12V
Have you tried hooking it up with our the resistor that came with it from ebay?

Do you have a multimeter or a voltage meter so you can see what the voltage is at the LED source on the window module?

The window module has a resistor there so do not use the one from ebay.
 

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Discussion Starter · #17 ·
i tried it with teh factory resistor but it didn't light up ......how do you use a multimeter never in my life have i used one LoL
 

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Not to hijack the thread but I have a small question if someone can answer.
I've been searching LEDs and I dont understand the numbers on them like 591 nm / 3200 mcd / 30 Degree Viewing(I know the degree part) but whats the difference between the above and 595 nm / 5000 mcd / 30 Degree Viewing? which one will be brighter?
 
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