Lets talk about LED's and powering them

[Seanz0rz]

These are the LED's:

http://cgi.ebay.com/100-x-Orange-Amb...item230c3a5f20


here are the specs:
* Wavelength: 605-610 (Amber Orange)
* Lens Color: Water Clear
* View Angle: 100-120 Degrees
* Forward Voltage: 1.8-2.4v
* Current: 20-30mA
* Size: 3mm Piranha
* Luminosity: 7,000 mcd

the plan is for a 15 LED array, 3x5.

input voltage will be automotive voltage, technically 12v, but can go up to 14.5.

the plan is to group it 3 in series and 5 parallel branches. or should i do groups of 5 in series (and 3 parallel) (which would be 12v at its max forward voltage) should i use a voltage regulator? or use a resistor? the pieces i have just use a simple resistor and are good for 9-14V. my math gives a 90 ohm resistor for that, approximately. and a 1 watt resistor i think would be necessary. thats all for 3 LEDs in series.

id like someone with some experiences with these lights help me out a bit. it all looks right and then again it doesnt.

maybe some reassurance on the math as well! im not sure what to use for the FV, if i should use the lower or upper limits, same with the supply voltage.

[troyboy162]

im not sure how dirty you can get away with them. but id start with strings of 7 in series asuming FV is V across the led and then current regulate them so they wont pop. 600 ohm 1 watt resister in line with each string? its been awhile...dont want to steer you in the wrong direction.

geeze im drawing a blank...i cant even remeber what forumlas to use, but i think the 600 is way off

[Robinhood4x4]

What are you using orange lights for?

Are you buying 100? If you are, then just wire them up and see if it works with just a resister.

[Seanz0rz]

this will be for front & rear turn signals and front marker lights.

i will be buying red for brake/park and white for reverse

basically the bulbs i bought royally suck, so im making my own.

looking for some good math so i can apply the same equation with different values for the FV so i can adapt the circuit for different LED's.

[troyboy162]

i suck but this page is good lol
http://led.linear1.org/led.wiz

[Obi..]

If/when you get the setup sorted post it up since I am still considering going to led's for a marker/turn integration on my '95.

*I like the Corolla setup I did, but I want to just clean up the front a little more and not have to buy those two bulbs every year the second I goto Tahoe and they go with the first Cold Snap. 2 sets within a year, all high quality bulbs, it's they just can handle the cold or maybe ice build up on them and crack as they warm up.

[MTL_4runner]

Having been in the electronics industry, I have a little experience with LEDs

If you wanted to run them at max brightness and given your LED specs, then you would use parameter like this:
Supply voltage = 14.5V (use a voltemeter on the truck to verify exact voltage)
Voltage drop = 2.4V
Desired LED current = 30 mA
Number of LEDs Connected = 15 (max you can go is 6 LEDs per string given 14.5V supply voltage)

This site is much better for drawing diagrams and sizing the resistors, just plug in the parameters above.
http://ledcalc.com/

Bottom line is that on each string of 5 LEDs powered by battery voltage, you'll need a 1/4 watt, 100 ohm resistor.

[Robinhood4x4]

This site is much better for drawing diagrams and sizing the resistors, just plug in the parameters above.
http://ledcalc.com/

Bookmarked.

[Seanz0rz]

thanks guys. looks like i have all the tools necessary.

next is just ordering parts and waiting patiently for them to get here.

here is a question for you. how should i design the brake/park lights?

should i have say 5 lights for the parking light, and all 15 hooked to the brakes?or should i do some kind of dimmer thing, where all 15 are illuminated but at half brightness with parking lights, and then brake lights fully illuminate the LED's. how would i do either?

[4x4mike]

Ken and I used LM317 for superflux circuits. All of mine are still in the garage but his are installed. He's only got 2 superfluxs' per LM317 but I you can add more arrays. The LM317's are cheap and the way to go.

I have some documentation but google: How to make a cheap 12 volt regulator.