LED conversion light

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OK I've just looked around the web at some sites that are using the Stars. I don't know how many of you are using switching supplies to drive the Stars like I am but I see a lot of specialized batteries (123's etc.). I've designed my lights to work on 3 to 4 AAA to D cells,Alks, Nicads, NMH. I found that two fresh cells at 1.6 volts each will drop to about 3.075 or so volts under the Star's load which is not enough to drive them. I didn't go with three terminal regulators in the flashlights because of efficiency, however in the house AC I do use them to simplify the circuits.
I'm running On-Semis 34063A driver chips for now and winding my own ferrites (E77 cores)with 20 to 22 ga. wire for the inductors. I'm getting over 85 percent and probably more efficency, although I haven't done indepth test yet. As I said before I set up for 250ma at about 3.2 volts with current regulation as opposed to voltage regulation. I have no noise problems and I set the output ripple to about 200mv. PP
I'm not using lenses or colimators either. I shape a cutter to machine out a solid aluminum 1-1/4 inch bar on my smaller lights that fit the Star at one end through the aluminum which is highly polished. I get an 8" intense circle with a mild corona at 5' distance from a wall. The circle is clean with no refractions or reflections. I sometimes put a flat clear lens in front of the machined aluminum reflector. I have not tried to get a finer beam as this suits my applications well and seems good for an overall light.
Your opinions are appreciated.
Thanks,
Rob
 
Rob,

Welcome.

I too am new and I also go for using NiMH's 3 cells or so. I'd encourage the move towards SMT. Many go for small and what has not been done yet. I like this. To give you an idea of the direction I'm going here is a pic of a 7W boost converter intended to drive a 5W LS LED's at 1A from 3 NiMH cells. It fits in a Mag 3D body and has been hammering for many hours walking the dog:

fbbd1154.jpg


The next project - 10W+. If it all works out I'll publish.

Again, welcome - you're not the only nut!

Chris
 
Hi chris,
Nice work!
1 amp boost is good in an SMT package. I'd love to see the circuits. I'll be using Atmel's AVR microcontrollers in my designs soon so I don't have to go with commercial switching drivers. Although I don't have the programming board to load SMT micros yet just DIPs.
I did design a voltage doubler circuit that has over 90% efficiency with one ferrite, two mosfets and two schottky diodes that is not bad in size for it's 2 plus amp output.
RobD
 
Rob,

What, microcontrolled! I like the idea. I found a site which within the post others mentioned other microcontrolled led drivers. Have a look and see if it gives any extra info you may want:

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB6&Number=261400&page=&view=&sb=5&o=&fpart=1&vc=1

BTW, what is your inductor ferrite/powdered iron core of choice? It's the hardest item to design/find that does the job the way I'd like it too. Given some DC offset, not all core data provides enough info and therefore theory rarely perfectly matches practice and I'm getting tired of the suck it and see approach. I do have some other inductors to try, but they'll take time to get samples so if you've found one already then that may help expedite my 10W job.

Chris
 
Hi Chris,
I'm using Amidon's E77 cores for some time now. I just purchased "Switch Mode Power Supply Spice Cookbook" by Basso but haven't had the chance yet to download the spice models and go through the programs. The magnetics look great and design time should drop with this book.
I use Atmel's AVR 8 bit RISC microcontrollers for most of my designs now even driving LCDs. I rarely use anymore TTL or CMOS 4000 stuff. In fact I use the Microchips instead of PLDs too. I was using Harris switching drivers but no the micros took over that too.
I run CircuitMaker 2K pro for all my magazine articles and spice simulations and TurboCad V8 for my illustrations.
Regards,
Rob
 
The AVRs are wonderful, although not too useful for 2-cell apps. (Unless they've added some 1.7v parts that have onboard ADCs - Previously the ultra-low-voltage parts didn't have onboard ADCs for current sensing.)

You should check out dat2zip's sandwich modules. The BadBoys are current regulated boost converters and fit in the space of a MiniMag lamp holder assembly. (i.e. are a drop-in mod for the MiniMag.)

georges80 has some nice step-down switchers for use in automotive lighting applications.

ElektroLumens typically goes with resistored and direct-drive Luxeon lights, although recently he's become a distributor for LED Supply's Micropuck boost converters, and is about to release a regulated version of the Blaster I.

Then you have LED Mods As Smal As Possible and 2-3 others that are pushing their way to the Final Frontier - Single AAA/AA Luxeon lights, including Mag Solitaire mods. (Admittedly not at full brightness, most of these run at .5W or less.)
 
I just got my Solitaire mod from LED ASAP Solitaire mod, and I love it. It is quite a bit brighter than the original, and a LOT whiter light.
 
Hi Andy,
Thanks for your comments.
I'm not exactly sure what you mean by "2 cell apps". I'm running a lot of AVRs on 2 cells, even Nicads at 1.2+ volts each with ADC The Tiny 12V can run down to 1.8 and my Tach jr. (www.dsgnspec.com) is running 2313s with Nicads as an option on my rev. 1 board out next week.I went back and forth with the engineers at Atmel on this but here's what I found:
I can run a 2313 at 2.5 volts 4meg as opposed to the 2.7v in the specks but I get about 10% of the chips that don't always work reliably. The thing is if a chip works at 2.5 or 2.4 volts chances are it will continue to work reliably. I don't take chances in my commercial designs but in my short prototype work I run with it.

I'm still using the On-Semi chips (34063A) for boost, buck and constant current apps. but I may go to an AVR H bridge configuration over SEPIC for higher efficiency. Although in theory you can get equal efficiency from an inductor compared to an xformer and SEPIC is quick to run off with low parts count. Nice for packing in a small light.
I did play with pulsing the Stars but couldn't see any real benefit. Also PWM direct driving a Star ran a low duty cycle from 6.2 volts (4 cells)which is what I run a lot of lights on, around 8%/92% if I remember, and current control wasn't great. It's something I'll have to spend more time on so I may be wrong about the pluses on this aspect.
Regards,
Rob
 
I have a Solitaire mod from LED ASAP. Great mod! /ubbthreads/images/graemlins/grin.gif Much brighter than the orginal and very white with the Q2K HD Luxeon. It draws 400ma at 1.2V and has amazing run time. 90 minutes in regulation on NiMH. Using an Alkaline AAA,
2 hours in regulation and over 8 hours in "moon" mode.
 
Hi RobD,

Welcome to CPF.

You will find we all try and share as much info as we can to help others, and with your experience with mod's and power supplies I'm sure your knowledge will be in high demand.
 
Thanks,
There are some things I'm still confused about. For one I see people using 1W Stars at one amp. The specks on this say 360 ma. is the max drive.
Also I looked at the Soltaire. I think it's a great feat to get in such a small package but if I read it right 700ma. load for 170 ma. drive has a very poor efficiency. Perhaps changing the mosfet will help. RDS(on) of .3 to .4 volts is low when todays mosfets are doing .015 and less even in SMT.
The problem with poor efficiency is that you don't gain a real benefit from the LED as opposed to a bulb when you start to take in the high cost of the LED and drive circuitry.
The 5W Luxeon is so high in cost that I'm not using it yet. I can run a small Fluorescent (4 or 8 Watts) much cheaper and at relatively high efficiency for a camp light, in fact I just saw a 4D camp light for $14.95 complete with a 4 watt Fluorescent.
I'm laying out the plans for an electric car and the 5 watt LEDs may play a role in it because I want to extract the highest light/power ratio I can get but at $43.00 they aren't going in any flashlights.
When they start running off millions of these and the price is $1.28 each then they become interesting.
Just my two cents.
RobD
 
[ QUOTE ]
RobD said:
Thanks,
There are some things I'm still confused about. For one I see people using 1W Stars at one amp. The specks on this say 360 ma. is the max drive.

The 5W Luxeon is so high in cost that I'm not using it yet. I can run a small Fluorescent (4 or 8 Watts) much cheaper and at relatively high efficiency for a camp light, in fact I just saw a 4D camp light for $14.95 complete with a 4 watt Fluorescent.

I can get but at $43.00 they aren't going in any flashlights.

RobD


[/ QUOTE ]

1) 1A => BIG Heatsink. A Luxeon 1W can survive high overdrive when you keep it COOL. Specs - who reads those /ubbthreads/images/graemlins/grin.gif

2) Those low voltage fluoro's are pretty pathetic - 4W fluoro is not as bright as a 1W Luxeon. I have a Side Emitter 1W driven at 350mA in a Coleman collapsible and it puts out about the same light as my Coleman twin 4W fluoro rechargeable camplight. A 5W Luxeon is MUCH MUCH brighter than an 8W fluoro running from 12V - so be careful when you compare watts...

3) 5W Luxeons can be had for about $26 or so from Future Electronics (the Lumiled distributor). But yep, they are still expensive for a 'LED'.

george.
My LED stuff
 
Thanks for the note. I haven't tried the side Stars yet and I'll pick up a 5 watter to see what it can do.
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/ubbthreads/images/graemlins/grin.gif
 
be sure to get a 5W, you won't regret it. These things are incredible. /ubbthreads/images/graemlins/grin.gif

Ah, btw. If you buy from future, you are going to enter the "dreade" luxeon lottery. If you got a U1W, that is all that you got /ubbthreads/images/graemlins/frown.gif . But you can also get a W or even X binned lux. If you would like a to know the bin before you buy, get one from here and here

they are slightly more expensive from future, but hey, you know what you are getting.
 
i think shifty means they're slightly more expansive than from future /ubbthreads/images/graemlins/wink.gif
 
yup Roth.
they are slightly more expensive than the ones from future, but you know exactly what bins that you are gonna get.
 
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