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I want to put LEDs in my projector housings for turn signals. I know how I'll do it physically, but I need to know how to do it electrically.
Basically, I want to put 5 of the brightest LEDs I can get, into each of the housings, to the outsides of the projectors. They will essentially be like the vertical LED headlights.
What I need to know is if I will need some kind of circuitry, or if I can just wire them all together, into the turn signal hot wire, and ground them.

yes or no.

The turn signal bulbs are 27 watts. With 12v, that is about 5 ohms of resistance, and 2.25 amps of current.

In order to use only LED's wired together, you need the resistance to add up to 5 ohms exactly(less or more will cause them to blink slower or faster), and the LED's to be able to handle 2.25 amps, and be designed for 12 volts.

Ryan wrote:yes or no.

The turn signal bulbs are 27 watts. With 12v, that is about 5 ohms of resistance, and 2.25 amps of current.

In order to use only LED's wired together, you need the resistance to add up to 5 ohms exactly(less or more will cause them to blink slower or faster), and the LED's to be able to handle 2.25 amps, and be designed for 12 volts.

Well put... He'd have to crack out the calculator and play with some parallel and series wiring equations. Not a big deal... I wouldn't want them wired in series though..

LED brake/tail lamps will not flash with thermal flasher units due to their extremely low current draw. Also, with stock flasher units, the turn signals may flash faster than normal (Hyper-Flash). These installations will require an electronic flasher unit. Try to find flashers designed to work with LED bulbs, they will say "LED compatible". Often HEAVY DUTY flashers will also work with LED bulbs.


Note that Ryan gave you the amps and watts of the stock circuitry. The number of LEDs will yield the amps. So you do not need to worry about how many amps the LEDs can handle, you need to not add any more LEDs than will equal 2.25 amps. However, that being said it takes alot more LEDS than you need to equal 2.25amps. You say you want the brightest LEDs you can get... no you don't. You want to get about 27 watts. Much more and it will be bright enough to blind people or at least distract them from other driving events... Using LEDs as signals is best if used in conjunction with LED reflector housings. If you look at "real" LED lighting housings on cars the LEDs are housed in a reflector just like most any other bulb. This is going to give you the best light for your LED. The LED housings are hard to find in my experience. However, you can get by without them if you line them up properly and maybe use another LED or two.
Wiring them in Parallel will be easier to do the math on and should work out better anyway.
I would suggest here for most all of your needs- http://www.superbrightleds.com/cgi-bin/ ... Fhobby.htm" onclick="window.open(this.href);return false;
this is the DIY page, which should be what you want, but they have other options like lighting strips that you can cut to legnth (number of bulbs) and some that have the bulbs sticking out so that you can mount them in some sort of housing if you want.

Thanks, guys! That's the info I wanted!
I would like to do bright LEDs without the reflective housing for 2 reasons; stealth look, and it would be too hard to cut the back of the projector housings to fit the reflectors. I was just going to drill holes the exact size of the LEDs, and and silicone them in place from the back.
I'm not good at math, but I'll try my best. I may PayPal someone some $$ to figure it out for me. I know, not very DIY, but the math part of my brain is broken. I will really try, though
Thanks again!

Okay, so they have a single bulb like this: •Built-in resistor for 12 Volt DC operation (9~14.8 range). I gues that's the voltage, but how do I determine what the resistance is?

You can't tell from that info. You need a power rating (W or watts), or a resistance (greek omega, or Ohms).

Or option 2 is to wire them in with the stock turn signals, the added current from the leds will not matter as leds do not draw a high amount of current. So long as the stock bulb is there then is enough current draw to make the mechanical flasher work just fine. I did this for several led accent lights on headlights I just wired them in with the existing turn signal bulbs and i works fine. Just be aware that if they have resistors built in it can influence the current draw. Higher resistance = less current draw. The mechanical flasher requires a set amount of current to make it work properly. Forumla's for resistanace, voltage and current;
I= Current
E= Voltage
R= Resistance
I = E/R
E = I X R
R = E/I
Think of resistance and ampage as a teeter totter effect, as current goes up resistance has to lower and vice versa. Mechanical flashers rely on current to heat the circuit to open/close it. So to answer your question if I am understanding you correctly is yes you can take the hot lead of the turn signal bulb T into that and run a wire to your leds to power them. Just make sure you wire it correctly with a soldered and shrunk tubed joint do not ever use those scotch locks to get your power they are the worst means of tapping a wire.

well heres an idea.
put the led's in. wire em up to the wires that hooked to your old turn signals.
and get a diff flasher.
thats the way i did it.
its still a little fast but with the led's i think it looks pretty cool

I'm no where near an expert in this field and there have been some very informative and helpful answers here.

What about these though:
http://www.ledlight.com/led-flashers-lo ... izers.aspx" onclick="window.open(this.href);return false;
I've seen these load equalizers work when used with the LED OEM replacement style bulbs and they make them flash like a normal incandescent bulb.

I did notice they do the LED flasher a bit lower down the page, which maybe better are you need 1 load equalizer per corner of the car so could work out pricey compared to the flasher which will just slot in where the original mech one went.

Thanks!
I was thinking about wiring LEDs together until they amounted to the right resistence, but I think that would be way too many! Is there a law about how fast turn signals can flash? I wouldn't be bothered by fast flashing.
Does the flashing slow down, according to resistance? I ask because I will have 11 LEDs on each side; 3 in the side mirrors, the 3 on the inner parts of the projectors, and 5 on the outer parts.
OR, does it not recognize anything below 5 ohms? If this is the case, can't I measure the resistence of all the LEDs, and then wire in a resistor?

Yes you can, just remember that if they are wired in parrallel it drops resistance, if they are wired in series it increases the resistance, for every led wired in parallel you will drop the resistance across the circuit, so keep that in mind when you measure it then add an appropriate resistor.

I don't know about the united states, but there is no d.o.t. flash rate here.