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Discussion Starter · #1 ·
To anybody who knows about car electrics/voltages etc. this ones for you!

I am trying to create my own LED indicators using 2 diodes per side. The diodes I currently have are 2.5w with a forward current of 50mA and I'm working on the cars output being 14v whilst the engines running. What I basically asking is what resistors I need to make it work. The circuit diagram I have so far is the one below but it only shows the resistance needed to run 1 diode, will it change when I run 2 diodes and how do I need to wire this all together to make it work??

 

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tdi power
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ask bertiebassit he may know or even stusy as he plays with this stuff all day long
 

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What are you actually trying to do mate?
Are you saying you want to use them as side repeaters when you say indicators?
Is it the flash rate you are trying to achieve?If you wired up a 522 indicator relay into your system it will flash at the desired rate regardless of what bulbs/led's you use.
Im confused but thats not hard lol.
 

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Discussion Starter · #4 ·
What I'm trying to do is used 2xLED's as front indicators on either side. I using the wires that went to the old bulb style indicators, but if I just ram an LED on the end of them that's not gonna work :D
 

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Yeah boyeeeeeeeee
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180 Ohms, assuming that the diodes are connected in series.

Each diode drops 2.5V, so two in series would drop 5V. This means the resistor needs to drop 9V (14V - 5V).

The current (40mA) flows through the resistor and the diodes, so using V=IR (voltage = current x resistance) we get:

9 = 50mA x R

Or:

9/0.05 = R

R = 180.

Power = I x V = 0.05 x 9 = 0.45 Watts, but best use a higher power resistor.

:D
 

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Discussion Starter · #8 ·
This is basically the components I have, plus I got 2x180ohm resistors because that was my first guess too.

 

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What I'm trying to do is used 2xLED's as front indicators on either side. I using the wires that went to the old bulb style indicators, but if I just ram an LED on the end of them that's not gonna work :D
You do know led's only go 1 way dont you? (yes i know your not stupid!)

Im no electronic genius but i cant see why they wouldnt work when you just plug them into a + and - ?
The only difference would be your flash rate would be faster when used in the indicator system?
 

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Yeah boyeeeeeeeee
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Does this seem like the right diagram now?

Yep, that's it. To be honest I can't remember which way round the LEDs go; it's been a while since I did hands-on hardware stuff (oo-er) - I seem to remember it's the 'little bit' inside which goes to the positive, i.e. as per your drawing.

If you get 'em the wrong way round they just won't light up; there'll be no damage.
 

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Yeah boyeeeeeeeee
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...i cant see why they wouldnt work when you just plug them into a + and - ?...
They would work; very well in fact. For a fraction of a second! :D

Any more than their rated voltage (in this case 2.5V by the looks of things) and they fry themselves, hence having the resistor.
 

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Discussion Starter · #12 ·
Cheers Andy, I'm assuming the flash rate will be fine whatever. I'm basing this assumption on the fact I have NO front indicators atm and the flash rate still remains normal. I don't know if this means ballast resistors have been fitted previous or what.
 

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Discussion Starter · #14 ·
To get it to work poperly you would need to impedance match the original bulb with a the correct resistor network....
I've just typed that into AltaVista's Babelfish with the output Language set to English, but I don't know the input language :confused:

Cheers for the help anyway lads, I can see I'm gonna have to just play around and see what catches fire :)
 

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Basically the original bulb would have an internal resistance/impedance the circuit you build would have to be the same resistance in order for the bulbs to work.... when I say work I mean flash at the correct speed.



First thing get a multimeter out and measure, its proabale going to be very very low as its a filiment
 

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Yeah boyeeeeeeeee
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Cheers Andy, I'm assuming the flash rate will be fine whatever. I'm basing this assumption on the fact I have NO front indicators atm and the flash rate still remains normal. I don't know if this means ballast resistors have been fitted previous or what.
Seems to suggest things may be cool then.

Out of interest, how are you mounting the LEDs etc.? Any chance of some pictures etc.? :cheers:
 

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Discussion Starter · #17 ·
I'll pop a detailed storyboard up when it's done mate, don't expect any great craftsmanship though :D
 

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Discussion Starter · #19 ·
Waahey, I did it! :boogy: :boogy:
Huge thanks for all the info from everyone :cheers:


This is what I ended up with, obviously before I sealed it ;)




And this is how it looks now, I have the invisible indicators I wanted :)

Click picture to see the video...............




Next stop is to go to the local MOT centre and see if this is within the law or needs modding more.
 

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Discussion Starter · #20 ·
Also they're much brighter in real life, came out awful on phone video :confused:
 
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