Help with Brinkmann 3AA direct drive.

I constructed a Luxeon Star 'pill' for my direct drive 3AA light. I cut down the LS star assembly, mounted it onto a copper washer, and place 3 ten-ohm resistors in parallel beneath that. I then mounted another tiny copper washer on the very bottom and soldered it to the resistors.

Supposedly the resistor cluster should give me 3.3 ohms.

The 3AA give 4.5 volts. The LS has max voltage drop of 3.42 volts. The delta voltage is 1.1 volts. A foreward current of 350 mA should then be produced if a resistance of roughly 3.3 ohms is place in the circuit. Right?

Well no dice. I hooked everything up and my multi-meter gives me a current reading of only about 110 mA !! WTF? Also, the LS is not all that bright, and the light produced is very wide, and lacks the intensity of my Opalec. I must be doing something wrong.

I tried running the LS without the resistors and it produced a brighter light, but the current was still under 300 mA!! Whats the deal, does the LS have a high internal resistance that no one mentioned in the spec sheet? This is getting frustrating.

Thanks for any help.

Direct drive fresh 3AA's should push about an amp through the Luxeon initially. Were all your runs done inside the flashlight barrel? If so, I'd wonder about how good the contact is between the barrel and the negative feed for the Luxeon. I found that considerable forward physical pressure from the batteries was needed to get a good enough contact to push the full current flow. BTW, 3AA's direct driving a Luxeon will very quickly overheat a cut down button unless it is heatsinked further.

Might also be a bum Luxeon. I did run into one which was about 1/6 the brightnes of my other ones.

Thanks for the reply.

I performed all measurements and tests outside of the light. Everything was wired and tested before installation.

I performed the tests without the resistor pack on another new LS and found identical results. I don't think its a bad LS, unless both are equally bad.

With the low current the light is currently operating with, heat is not a problem. I did notice that the LS heated up rather quickly when operated without resistors. I was hoping to use more copper washers as heat sinks and to increase the surface area contact to the aluminum flashlight housing, but I ran out of room. Those damn resistors take up too much space. There has to be a smaller size resistor that can handle the 1 watt power. The heat transfer should also be aided in the final product with some heat tranfer goo that I got.

Just my 2 cents about a 3 AA Legend, I have no time to investigate its probability but while you are tinkering with the 3 AA could you check out any reasonable way to install 5 "N" cells?
This would be a direct drive for the 5 watt luxeon, thanks. I have a feeling it may work for a short run but amazingly bright LED in direct head to head light output of a P61 HOLA.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Avatar:
I constructed a Luxeon Star 'pill' for my direct drive 3AA light. I cut down the LS star assembly, mounted it onto a copper washer, and place 3 ten-ohm resistors in parallel beneath that. I then mounted another tiny copper washer on the very bottom and soldered it to the resistors.

Supposedly the resistor cluster should give me 3.3 ohms.

The 3AA give 4.5 volts. The LS has max voltage drop of 3.42 volts. The delta voltage is 1.1 volts. A foreward current of 350 mA should then be produced if a resistance of roughly 3.3 ohms is place in the circuit. Right?

Well no dice. I hooked everything up and my multi-meter gives me a current reading of only about 110 mA !! WTF? Also, the LS is not all that bright, and the light produced is very wide, and lacks the intensity of my Opalec. I must be doing something wrong.

I tried running the LS without the resistors and it produced a brighter light, but the current was still under 300 mA!! Whats the deal, does the LS have a high internal resistance that no one mentioned in the spec sheet? This is getting frustrating.

Thanks for any help.<HR></BLOCKQUOTE>

Sounds like you have a certain amount of resistance in your circuit/connections somewhere. If you have a digital voltage meter, see if you can check what kind of resistance is present. Remove the batteries for this test. Connect the DVM to the points of positive and negative connections, and see what resistance there is. There should not be any. Also, if you have a way to connect the batteries outside the flashlight, and connect them to the LS, completely independent of the flashlight.

There shouldn't be any need for adding resistance, if you heat sinking is good, unless you just want to reduce the light output, and extend battery life. I sometimes run the LS from 3 'D' cells direct, at 1.5 amps! As long as the heat sinking is good and the LS stays cool to mildly warm, it seems to be okay.

Test the condition of the batteries under load, or, just replace them. Three AA's should make that LS burn holes in doors!

Wayne www.elektrolumens.com

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR> Well no dice. I hooked everything up and my multi-meter gives me a current reading of only about 110 mA !! WTF? Also, the LS is not all that bright, and the light produced is very wide, and lacks the intensity of my Opalec. I must be doing something wrong. <HR></BLOCKQUOTE>

I not sure how you are hooking up your meter but, if you are using your meter in current mode, the meter sense resistor could be adding additional resistance you are not taking into account.

The best way to measure the current to the LS is to measure the voltage across your three resistors and do the math to calculate the current. (Volts / Resistance = Current)

I did some quick math and came up with 14.5 ohms computed for your setup. Sounds like you have your meter in series and in the millamp range which is probably injecting another 10 ohms in series.
(10 + 3.3 ~= 14.5)

I agree with Wayne. If you can heat sink to the light body, go direct drive. I wouldn't want my Blaster any other way. TX

Thanks for all the great help, everyone.

I'll retry the current measurement via calculation instead of directly. I'll change the added resistance to whatever gives me 350 mA and if I don't like the brightness, then I'll go crazy and remove all resistance.

I'm going to go to the EE department labs to do this work. They have all the equipment I could ever need. I'm an ME, but sometimes I like to dabble in the second-best field of engineering.

As far as the 5 N cells, I can only tell you the dimensions of the case. I don't have N cells, but what you propose with the 5 W LS is pretty tempting. The case will allow nearly 15 cm (about 6 inches for those that like units you can actually get a feel for)of room from the very top (with internals removed) to the base, leaving the necessary room for the tail cap switch to operate. I hope N cells are no more than 3 cm long.

Direct drive with 3AA's is in my book the way to go. With good heatsinking, it is fine and super bright. If you want long life, a few Nichia's would be fine, but a Luxeon just begs to be a light blaster - not an endurance candle.

I only have one LS (white with new optics). When I first hooked up 3AA's to it (with I believe 1.8 ohms) all I could get was about 240 ma. My four cell AA battery pack came with 26 gauge wire, and the spade terminal I hooked my meter up to got hot. I did not have the LS heatsinked to anything else. I should have changed just one thing at a time, but I changed all my wiring to 22 gauge(tinned) and put the LS on a large heatsink from an old TV (it would cover the palm of my hand). With fresh batteries, current through the LS reads 500+/-10 ma (oh yeah, I put in 1.5 ohm resistance). Current falls pretty rapidly, after about an hour and a half the current was down to 250 ma. I only took one reading and I could have had a poor connection with my meter. Anyway, I have to agree with all the threads about proper heatsink, as the light output of a mod I'm working on with 1.5 ohms and 3AA's isn't nearly as bright as that large TV heatsink.

I hooked up my 'pill' to a voltage source at school. The voltage supply had both voltage and current meters built in.

When I set the voltage output to 4.5 volts, and connected it to the LS module, the current supply was indeed 350 mA on the money! So at least the calcs were correct, and my module does not have any problems.

The problem is that my LS has no optics, and while it does put out a decent amount of light, it is too diffuse to be much use. In the interest of improving light output, I bypassed the resistor cluster, and connected the 4.5 volts of the voltage supply to the LS directly. The current went up to about 1.5 Amps or so, and the light was significantly brighter.

The trouble was that it got too hot to handle in less than 10 seconds. This device is going to need some awesome heat transfer consideration.

This light is not going to be on for long durations, but I would want at least 2 minutes of continuous light before it became destructively hot. I am going to have to be carefull when I finally install it.

Does anyone have a solution to the diffuse light problem? Are there retro-fitting optics available or anything that will collomate the light? Right now, my Opalec New Beam produces a much more practical beam than my 3AA LS!

Avatar,

The Luxeon optics will fit perfectly in the Brinkman head; it would be your best bet for a nice beam.........

Thanks for the info on the optics. Does Mark Hanna Surplus sell them? I'll go find out.

Hey,
You guys are missing the point. With alkaline AA's the internal resistance of the cells is what's honling things back!
My first test of an LS got me about 170mA from 3 fresh energizer AA. That is not the case with a cell which has lower internal r, such as NiMH or NiCd. Direct drive with resistors is easy, but gives poorer overall performance. Once you get the hang of keepin yer LS cool, check out some of the relatively easy DC-DC converter ideas floating around. The kick butt compared to direct drive.

Rod Weeks,
I think you may be missing the point. I don't fault anyone for going to a DC-DC converter (if they have confidence in it's reliability). I may gain enough confidence in them myself over time (I know very little about regulated circuits). Might even do a mod that would contain a DC-DC converter with direct drive backup (if that's possible). I primarily want a flashlight to work when I turn it on. At this point I'm not concerned about having a super bright light (perhaps other direct drive people feel the same way). The performance of a luxeon star at factory specs is so far ahead of a lot of choices in flashlights. At work I'm working on equipment that relies fully on the very latest and best electronic technology. I can't think of an example when a failure has put someone in harm's way (no harm, no foul). I want a flashlight to work as reliably as possible. A failure with a flashlight might put me in harm's way.

That's interesting that you only got 170 ma from an LS with 3 AA's. What resistance were you using? With 1.5 ohms I have been getting 500+/-10 ma with eveready "cat" alkalines and rayovac maximum alkalines. Yes, current falls off fairly rapidly to about low 400's. I have no experience with rechargeable batteries, but the internal resistance of alkalines so far has not been a big problem.

The more I experiment with the LS/o that I have the more I'm convinced that any given flashlight design (metal) will have its own balance of cooling capability, brightness and longevity (speaking of direct drive). The same may be true of regulated flashlights (I don't know enough about them). I think the most important part of the LS is keepin' her cool!

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Rod Weeks:
Hey,
My first test of an LS got me about 170mA from 3 fresh energizer AA. That is not the case with a cell which has lower internal r, such as NiMH or NiCd. Direct drive with resistors is easy, but gives poorer overall performance. <HR></BLOCKQUOTE>
That's interesting, -I just tested (DMM) the current draw from 2 of my Luxeons (no resistors) with 3 Energizer (almost fresh) AAA alkalines. The meter showed about 540mA for the first 10 seconds, and then dropped down to 450mA, where it leveled off and held steady (for a 5 minute test).

-With 3 freshly charged Nexcell Nimh AAAs measuremrnt was 650mA+

Both of my Luxeons (an early white, and newer Royal Blu measured about the same).