Greetings from a newby and a preview of the torrential questioning that will come....

[SwaggeringPagan]

Hi guys, this looks like quite a place, enough info floating around here to be pretty overwhelming! So I'll get right to it, if that's ok? I build custom motorcycles and hotrods, it's been mainly a hobby until recently and I suppose that's even a bit of an overstatement. In truth I own a machine shop and do mainly custom fabrication for motorcycles and hotrods though I've built a few of each for real live paying customers. I'm presently neck deep in a cafe racer buildup for a local kat and find myself at a point where some info would be helpful to me. I've got the bike down to a running/riding weight of 320lbs (from 465) and that in an of itself helps a 30 year old engine and chassis perform much better. In that quest for weightloss I shed the bulky and heavy factory lighting for some one-off pieces that I stashed some ebay white LEDs in using the colored lenses take care of the rest. This allowed not only several pounds to fall off but offered a significant reduction in current load to the already somewhat questionable Honda charging system. I recently experienced the light output from a converted 2 D-cell Maglite and was quite impressed. What I'd really like to do is build an LED headlight array that would be stashed inside the OEM headlight shell.I can make a clear non-focusing bubble lens to protect the works but it looks like perhaps it won't be as simple as I'd thought. Can anyone shed light on or point me to a quick tutorial on the LED drivers that I've seen mentioned here? What do they offer that I can't get from directly powering the leds? What about the various LED makers/sellers out there for the LEDs and reflectors? I've also seen heat sinks mentioned and the idea strikes me as odd since my experience with LEDs tells me they don't put out much heat in comparison to incandescent bulbs. So thanks in advance for any assistance you care to lend! Lee

 

[mds82]

Welcome to the forum. i've been making some auto lights for a while now so i figured i could give you a hand with this. First off sounds like you got the idea right in saying that you need a driver for the LED's versus running them directly from the battery with a resistor.
there are 2 types of drivers, boost and buck. boost drivers take the input voltage and boost it up ( 13.5V in, and 14.5 - xxx V out) The other driver is a buck, which will lower the output current. IE you will ahve 13.5V input, and almost 0 - 12V out.

with that in mind, the average high power LED runs at 3.7 volts. So you can either run 3 in series ( 11.1 volts) with a Buck driver, or 5 or more ( 5x3.7v) with a Boost driver ( depending on the driver you choose)

LED's do need a LOT of heatsinking, so you will need to modify the current housing to both mount the LED's and also allow them to heat sink. High power LED's can run at 1000ma, whereas small led's run at about 20ma. If you were holding a Cree XR-E in the palm of your hand(a bare emitter without a PCB) and running it at 1000ma, you would probably burn your hand within 5 seconds LOL

What size is the OEM lens, or what size do you want to make the light. the LED's will come pre-mounted on 3/4 PCB's so you can arange them however you want. You will also need optics / reflectors to control the light output.

brand's of LED's on the market: Luxeon ( they make the Rebel and the K2), Cree ( they make the XR-E) and Seoul ( they make the P4)
http://luxeon.com
http://cree.com
http://zled.com/_homepage/home_eng/asp/main.asp

Hopefully thats a start.

 

[TorchBoy]

First off sounds like you got the idea right in saying that you need a driver for the LED's versus running them directly from the battery with a resistor.

The efficiency will actually be about the same if you're using a series of three LEDs - within 5% unless you're talking about a poor driver. "The right idea" referred to isn't really so "right", but it can give a few more options, like driving ten LEDs in one series.

there are 2 types of drivers, boost and buck.

Linear, buck, and boost - makes 3 types. :nana: A linear regulator drops unwanted volts by basically dissipating it as heat. It works as an automatically variable resistor and in the case of three LEDs driven from a 12V lead acid is likely just as efficient as anything else might be.

 

[SwaggeringPagan]

Argh! I dunno where to start on this now. Crap!!

Ok so it seems my info on LEDs is pretty out dated. I've got a handful of white leds here in the shop that I've used on other non-critical lighting projects that barely get warm at all....obviously things have changed.

I have a few housings on hand to work with, since this is a custom build. I have a 5", 6", 7" and an interesting old 9" to choose from. I'd have a clear non-fluted lens made to suit.

The drivers sound a lot like DC-DC converters to me. I take it the general practice these days is to run them in series to get close to the voltage rather than use limiting resistors? Why?

 

[mds82]

the original oem bulb, what is the wattage of it? i would assume a 55watt halogen.
if so, 55 watt * 24 lumen/watt = 1320 lumen. I would assume that you want to make the new light as bright if not brighter then the original. If so here is what you can do, you can get 5 Cree XR-E Q5 binned LED's here. each one is rated at up to 228 Lumen when driven at 1000ma. I thought it was up to 250 lumen though. that would give you 5x250 = 1250 Lumen.

Then you need a driver and optics for it. For a driver - you can use this one. Its called a the Shark. you can connect all 5 of the LED's in series, and use the 12 volt car power system. On the driver there is an adjustment, you want to turn it all the way up.
Optics - Now what do you want the light to look like?? do you want all the light shining directly forward, do you want a small flood, do you want a full food.

last is heatsinking. I'm pretty sure you will need something larger then a computer heatsink to keep these cool.

 

[Ken_McE]

Ok so it seems my info on LEDs is pretty out dated.

That's OK. By the time you start on the next bike they'll have changed it all again. Don't worry about it.

I've got a handful of white leds here in the shop that I've used on other non-critical lighting projects that barely get warm at all....obviously things have changed.

I would speculate that the ones you have pull milli-watts, and the ones we're describing here are measured in whole watts.

The drivers sound a lot like DC-DC converters to me.

Yep.

I take it the general practice these days is to run them in series to get close to the voltage rather than use limiting resistors? Why?

LEDs are rugged in some ways, delicate in others. On your bike we expect the current to wander up and down a lot. If you have current going direct to a resistor then the LED, the LED will brighten and dim with the current. If you have too strong of a resistor then the LEDs will run dim a lot, which sucks for the driver. If you have too weak of a resistor they'll run real bright, but you'll get a lousy lifespan and be pissed about having to replace expensive parts. The job of the regulator is to run them consistently at the maximum safe (safe for the LED) brightness so you get both brightness and life expectency.

 

[Changchung]

Hi, welcome to the forum, check this out what I do to a friend in a Yamaha R1, I use just resistor, no drivers, is a good option too, I have lens, but this Leds K2 are very bright, so, I dont put the lens to this Leds, not need it...

Check this out and let me know if I can help you in anything...

http://www.candlepowerforums.com/vb/showthread.php?t=186138

For the head lights you can use this kind of Leds, maybe 6 with lens you will have a good result...