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Hello Im new to the forums over here but damn you guys have a lot of information. Ive got an 02 Si and ive been over at ephatch.com. Anyway Im doing a Blue LED swap for my cluster, climate controls, ect.
I have not done the gauges yet but I have done the climate controls in the center dash. I used 4 LED's in series with no resistor, in place of the normal bulbs. (I sanded them down too) It works great, looks really nice and bright with excellent light diffusion. My question is that everyone else who does the LED swap seems to use resistors. Ive measured the sources with a multimeter & have done all the math and 4 resistors in series does not reqire any resistance. I want my gauges nice and bright & want @ least 4 LED's in place of the stock bulbs. Does anyone know why I should not do this? like will the LEDS burn out faster or anything? They seem to be just fine

using Blue LEDS

3.5 foward Volts
20mA
4 LED's in series = 14 foward volts

I dont think amperage will be a problem as seeing how we are working with a 12 volt source in our componets

Just my 2 cents

ill post some pics of my interior when done!

 
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Try it and see what happens. I've heard that if the LED is getting a higher forward voltage, they may not last as long. For the gauge lights, I used indiglo wires to light it up, since LEDs don't give very even lighting. Check my sig link for more info.

 
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The resisters are only there for the voltage drop, if you have the right voltage, everything should be fine

 
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Its called a "current limiting resistor." Its used to limit the current in the LED's, to prevent premature failure...

 
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The total voltage required to run the LED's at full tilt is 14v, and Im running 12 volts to them - so the 4 LED circuit is technically limiting current. Anyway the climate controls have been fine for a week now, I really can't wait to get into the gauges!

 
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In your setup each LED is getting the same amount of current since they are in series. The amount of current that the LEDs are getting depends on how much voltage is dropped across them (in your case 12v). The LEDs in no way will limit the amount of current flowing through the circuit if either A) a surge occurs, or B) a short occurs. Installing a resistor is more of a matter of safety / protection as well....Just some advice, as I personally wouldn't wire anything up half assed myself.

 
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A surge in current will have no effect what so ever on an led. An LED works of mA. The led will only take the amount of current that it needs to run. Your cars alternator puts out way more current then any LED could ever use so dont worry about current. A resistor is uses in an led setup to limit voltage so it doesnt burn out. 4 of them wired together in series is fine and you shouldnt have any problems with them wired like that, but if eventually 1 does burn out then they all go out.

 
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You just contridicted yourself here. Current = Amperes (or mA if you like).

Resistors don't limit voltage - they limit current:

I=V/R

They CAUSE a voltage drop due to their nature.

Read more here:

http://www.electronics2000.co.uk/dat...sgl/LEDres.htm

 
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Hey I dont wire things half assed! All my connections are good solider joints with heat shrink tubing. I also took the time to shave down and rough up the LEDs with a dremel so they diffuse light better. Quality is not the problem here, my dash looks astounding. Im just saying 4 LEDs in series has enough resistance to handle the current

I = v/r

I =12v/720 ohms

I = .016 or 16 mA

so even with a spike in current or voltage the circuit should be just fine.
I would just rather have one more LED in the circuit in place of the resistor because i like my gauges bright

 
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Post pics of this Dash Lighting that you did! I want to see (I'll probably do it to my Golf if I can find out how.)

 
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i never took a look at the dash lights but isnt it harder to wire up all teh leds in series than to use a current limiting resistor for each led?

to wire up the leds in series, you'll have to run a wire to each led etc...sounds like more work than neccessary...

 
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The point i was trying to make is that you can have a circuit with 10 amps or 10000 amps of current. The LED only takes what it needs which is maybe 50 mA. Current has no effect on whether an LED will blow or not. Just like a cd player that uses 10 amps wont blow because the alternator puts out 80 amps.

4 leds can be jumped straight across a car battery with is 500-600 amps and be fine, its been done. Voltage is the main issue.

 
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if you have one led hooked up to the battery, it'll blow..i gurantee it...leds cant choose to restrict current to 50mA. super bright leds can have a safe voltage drop of approx 3.3Volts(depends on the led's specs). if you apply more than that amount of voltage to it, it'll try to pass way more than 50mA of current. overcurrent is what kills the led.

the reason people add a resistor in series with each led is to limit current. to calculate the resistor value, you need to use ohm's law. you want 3.3V across the led so 12v-3.3V = 8.7Volts drop across the resistor. you also want 50mA of current (assuming that's the amount of current your led can handle) so 8.7V/50mA = 174ohm resistor


go read about how series and parallel circuits work, along with kirchoff's voltage law

and if you are a keener, go learn all about AC circuits...that stuff is a biatch...

 
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let me try to explain some more..heh

the LEDs are parallel to the circuit with 10amps etc...

voltage is the same across all the elements in a parallel circuit. ie. 12 Volts across your power terminals on your amp, and 12V across the terminals on your alarm etc.

each individual element in a parallel circuit can have a different amount of current traveling through it. the amount of current depends on the voltage across the element and how much resistance the element has.

in a series circuit, the current going through each element is the same as all the elements in that series circuit. current in a series circuit is limited by the resistance of all the elements. the resistance of each element stays constant and depends on the nature of the element. ie. a 10ohm resistor will have a constant resistance of 10ohms.


btw, voltage is the ability to push current through a circuit. if the circuit has a high voltage applied to it and the circuit cannot "resist" the flow of current, then too much current is pushed through the circuit therefore it will burn. current is still what kills it. people have been shocked with thousands of volts and still live because not enough current passed through them and the current didnt pass through their heart.

 
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Pics damnit!

 
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Um well ok, lots of good feedback, the circuits are still fine. I did buy some really high end LED's manufacturer direct, but so far resistors seem unneeded. My gauges are completely dissassembled right now and should be back together by friday. Im thinking blue with white needles but ill prob just do blue/blue as seeing how i have 80 blue LED's here to use. Ill take pics as soon as it gets dark and complete

 
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4 leds in series should work fine...

i just dont see the point in having them like that..heh...i think it would be annoying having to run wires from led to led...just my opinion

 
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Heres some pics of my EP2 with blue dash lights, done more since these photos but haven't got any pics yet...







They are 3 leds with resistor and 2 leds with resistor in other places.

I always use a resistor when wiring my leds as more of a safety thing.

I don't think 1 led would make that much difference, and a bit hard to cram 4 leds into a space 1 bulb was in!

more pics here http://civic.recognitiondesigns.com/interior.html

 
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Well im finally done. 0 resistors. This has taken me a good 8 hours for everything. Not bad for my first try. I ended up putting 20 LEDs in there all spread out around the cluster. Ive got a little more work to do to them but im done for tonight. Here is my EP3 dash now!

 
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hey Shock, that looks good! for the guages, did you remove the orange/green filter behind the numbers? are you using 5mm leds? I've just got the guages to do now so a little help would be great!