Lets talk about LED's and powering them

[Seanz0rz]

These are the LED's:

http://cgi.ebay.com/100-x-Orange-Amber-Piranha-Superflux-LEDs-3mm-Dome-LED-/150529007392?pt=LH_DefaultDomain_0&hash=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.

[Seanz0rz]

im familiar with the lm317, last year i built a variable voltage power supply in my electronics class. its actually what im using to test alot of these circuits.

i know the voltage in the vehicles will vary from something like 11 to a max of 14.5. the low end doesnt matter to me, because it wont hurt. but the spike could. i am ultimately designing these to be durable. i think i will experiment with the resistor and see if it performs like i want.

thanks for your help guys.

[4x4mike]

ledsuppy.com has the drivers I got for my other projects. They are good drivers but expensive. The newer ones I've tried are the buck toot's at 350ma for my red cree dome light.

[MTL_4runner]

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?


What about something like these instead?
http://cgi.ebay.com/ebaymotors/1996-2000-TOYOTA-4RUNNER-RED-CLEAR-L-E-D-TAILLIGHTS-LED-_W0QQcmdZViewItemQQfitsZModelQ3a4RunnerQQhashZitem 45f40b5f10QQitemZ300447129360QQptZMotorsQ5fCarQ5fT ruckQ5fPartsQ5fAccessories

[Seanz0rz]

ledsuppy.com has the drivers I got for my other projects. They are good drivers but expensive. The newer ones I've tried are the buck toot's at 350ma for my red cree dome light.


what on god's green earth is a "buck toot's"?!?!?!?!



What about something like these instead?
http://cgi.ebay.com/ebaymotors/1996-2000-TOYOTA-4RUNNER-RED-CLEAR-L-E-D-TAILLIGHTS-LED-_W0QQcmdZViewItemQQfitsZModelQ3a4RunnerQQhashZitem 45f40b5f10QQitemZ300447129360QQptZMotorsQ5fCarQ5fT ruckQ5fPartsQ5fAccessories


Jamie, i have considered those, and i might buy a set to see how they are.

however, this led project isnt so much for the 4runner than it is for the vw. i have been wanting to put LED arrays in the 4runner for years, but the vw is a more pressing issue as i want to keep the power consumption as low as possible (35A is what i have to work with on that vehicle)

i purchased the 30 LED drop in lights, they are absolutely terrible, i am so disappointed i spent so much money on so much crap. and i have exceeded the return period as well. they will get used in other projects somewhere, but basically i burned about 100 bucks on this one. live and learn.

next week ill order some of my parts and all of my LED's. i will prototype it on a breadboard, then solder it all up on a protoboard and test it extensively. then i will likely make some PCB's (either on my own or through a company). from there i might sell them on the VW boards. and i will likely make a set for the 4runner as well, and see what the interest is in those (probably much lower than the VW crowd)

[Robinhood4x4]

buck toot

http://ledsupply.com/bucktoot.php

[Seanz0rz]

ahhhh ok. i thought it was something like "the bee's knees"

yikes! 10 dollars each! that would be 60 bucks just in vRegs alone.

[Robinhood4x4]

Aaaahhh great!! Now you guys have me looking at LED websites again. I need to make some backup lights, general area lights and a mtn bike light. Bastards.

[troyboy162]

haha im looking back into making a light too. three cree xm-l leds and a dirty current regulator...any way i cut it, its not price effecient after i figure in my time vs those nice kragen hids

[4x4mike]

ahhhh ok. i thought it was something like "the bee's knees"

yikes! 10 dollars each! that would be 60 bucks just in vRegs alone.


Yep I have $50 dome lights (each), 4 total between 2 cars. $100 rock lights, underhood light, etc as the list goes on. They are much better than anything drop in, they are efficient and custom which fits the bill perfectly.

[paddlenbike]

I am constantly disappointed by LED products I find on the market. With incandescent you can just buy something. With LED you have to do your research. Almost all drop-in lights are pure crap...they have the blueish color, have no voltage or current regulation and simply don't last. I pretty much only buy Cree LED products now because they have proven themselves to be high quality and with good CRI. I love everything I have from that company from flashlights to recessed lighting in my home to the circuits I have built for the 4Runner. I went so far as to buy their common stock. I do like Superflux though, and I don't think I will ever buy another 5mm led in my life.

I haven't looked but I don't think they make the bucktoot, luxdrive, etc. drivers in lower drive currents, as in less than 350mA. Because there can be a 25% variance in input voltage between vehicle off and on, I would make an LM317 circuit. Build it right and it will last forever, unlike the chinese led products. My superflux floorlights have been installed for I think three years now and I haven't touched them, ever. And they continue to draw praise from the drunken holiday partygoers I've been driving home lately. You can build a super reliable superflux/lm317 setup for less than many junky drop-in kits cost.

Use the highest voltage for your calcs. The only thing that part of the calculation does is figure a worst-case scenario for heat dissipation, where a 0.5W resistor might be fine at 11.8V you might need a 3/4 or 1 watt resistor at cold-start up when the truck's alternator can be putting out over 15V. My superflux leds are rated at 80-100mA max and I am running them at 62mA. There is no noticeable heat output and the light output and color are great.

[slomatt]

Sean,

Keep in mind that LEDs should be run off of a constant current source. This kind of power supply provides a fixed amount of current and varies the voltage as needed to maintain that current. It's used with LEDs because as they heat up they draw a higher voltage so you need to limit the current to keep the voltage in check.

One problem you are going to run into is that if you run chains of LEDs in parallel you will wind up with unequal current going down each branch since the resistance (and hence voltage) of each LED varies. If a LED burns out and you loose one branch it will greatly increase the current going through the other branches.

For higher power (350mA+) LEDs I'm a big fan of these current sources. They sell models ranging from 350-750mA and I've had two in my truck for over a year with zero problems.
http://www.dealextreme.com/details.dx/sku.13557

Since your LEDs draw a relatively low current one option would be to simply put a resistor inline to drop the voltage and leave enough of a buffer with the current that you don't burn them out. If you run a single resistor per trunk of 5 LEDs it will allow for more equal current distribution. Alternatively you could use a LM317 (or a low drop out substitution) to make a current source.

- Matt