So I’ve got this cool light and I want to upgrade it. It’s 3v 6 AA. Direct drive as you can see. The star is 20mm. That aluminum plate it mounts to is 3mm thick. Sadly it’s a little lose when placed on the thin shelf so there is little edge contact to the body. The switch is 3 position, off, momentary by using the button above the switch, and on. So I’m looking for suggestions on what I could do with it.
I’d really like to put a 5000k lh351d in, but am not sure if I can.
Image links below. They were showing blank in the preview when trying to post as images. I think because of the links.
Yeah, you can do that no problem. Either reflow the emitter or buy one already mounted to a star and just replace that. If I had to bet, I'd say your six cells are wired 3S-2P giving your 4.5 volts out, then the small wires and two resistors reduce that a tad so the emitter doesn't cook. If it's really 2S-3P giving you only 3 volts that will still work, sorta, but you won't get much light and if that were the case I'd probably remove those resistors. I did something similar with a cheapie light that uses 3AAA in a carrier that gives 4.5 volts. Put an SST20 in it and a 1 ohm resistor and it turned out pretty nice and usable.
As for the large star, I wouldn't worry about it not contacting the body...won't be generating enough heat for that to matter on this one. You could try shimming it with thermal silicone chunks if that will still allow the reflector to sit correctly, but I wouldn't bother (and don't use wadded foil or anything...very poor conductor). When you reassemble things, a light dab of some sort of thermal paste is a good idea between the led star and the large star.
Also...the plastic centering gasket for your emitter. You'll probably need a new one so look for a standard 3535 gasket (3.5mm x 3.5mm, which is the size of the die for the LH351 emitter and many others, also often sold as XPL size) and get one that has a round diameter that matches the size of the hole in the reflector (7mm, 9mm, etc). There's a chance the one in the light now might work if the new emitter will still sit at the right height. Be sure that however you go about that, that the reflector doesn't short/contact any solder points or bare metal beneath it (always true if it's a metal reflector although sometimes just the metal coating on plastic can do the same). If there is extra space where the reflector won't sit snugly after tightening everything back up, sometimes a thicker lens or a thicker o-ring can solve that...or possibly you could shim beneath that large star if there's a good way to do that. We're usually only talking millimeters here but sometimes it matters when you reassemble. Many of the cheap emitters have thicker bases than what's on the LH351, etc. Kaidomain has a lot of reflectors available, too, so if you can't get things to work right away it's possible that you could find a slightly taller reflector that will still fit the host.
Correllux! A ton of info there, thank you. I had not considered it could be 4.5v. I assumed it was 2 banks of 3 like the carrier is configured, but 3 of 2 makes sense too. I’m not sure why I didn’t think of it. The light is rated at 400 lumens and the LED is a Cree.
Another interesting point is there is a ton of room in that head. I could add a driver and take advantage of the momentary button for mode switching. I will measure the thickness of the star the LED is mounted to as well to be sure the new one won’t sit too low.
The light is really solid and has interchangeable colored lenses and everything. It’s really cool!
Take a look at those battery holders and see if you can tell how the contacts are wired. There are lots and lots of those types of holders and sometimes they aren't easy to tell at first glance. Or just take a reading with a multimeter using fresh cells. If your meter can measure DC amperage more than a few milliamps you could also test at the led wires to see what current you're actually getting up there (probably a way to get that reading with another method too but often these lights don't use the body to conduct electricity like most lights, just using those battery carriers to do the whole job and making both + and - contact on a basic (or even empty) board).
Putting another driver in there could work fine as well but I think you'd still want to keep it pretty low current since the heat sinking is pretty poor here. The switch needs to be able to handle the current as well, and have solid reliable contact (some sliding switches aren't so great).
Hard to see what emitter you have now but chances are good that it may not be very efficient and needs higher voltage, so the Samsung will gain a little bit there by probably giving you some longer run time and perhaps a little more lumens at first. Being direct drive of course these just taper on down gradually and quickly as the cells deplete. You can change the resistors to vary the output/runtime a little. I tried 1.5 and 1.2 ohm at first but the 1 ohm seemed to be just fine with a little more light output.
Thickness of the mcpcb (led star) probably won't be any different here but the height of that gasket is what I was getting at...where the reflector sits on top of it. The new led/gasket may sit lower overall. There are some extra thick mcpcbs out there but I don't know who has them these days. So basically we're looking at the thickness of the "hat brim" of that plastic gasket. Simon from Convoy has a few types (with good photos) on his aliexpress store but there is a larger selection at Kaidomain or their aliexpress store "LHT Flashlight Store." Domestically, Richard at Mountain Electronics stocks just a couple of the most common types...I think Mohr Lumens and JC Customs may also have some for sale. Hard to find these little bits in the USA. They're one of those handy and somewhat essential parts for modding and if you aren't just straight parts-swapping in a light, it pays to have several types around to have on hand for problem solving, and you can alter the gaskets to suit if need be...and they're cheap. :)
When I was a kid we all had those lights, except only a few were military surplus made of metal...most were plastic copies. All of them had very weak incandescent bulbs. But the lenses and sos blinking from across the neighborhood! Great fun. :)
It’s definitely not using the body, so I will test that way. I looked up the resistors and they are 13 ohm. So I’m betting you’re right and it is 4.5v. I will measure my gasket and get a few potential replacements. Probably from Kaidomain since that is where I was looking to get the LED from.
Yeah, this one is a JobSmart from Tractor Supply! My buddy got me one because he thought I might be able to improve it. They were only $14. The body is aluminum and not cheap pot metal like some are.
Fair point on the switch, but I wasn’t looking to boost, but maybe to gain some lower levels with the driver. Don’t always need full bore.
Btw, the LHT Flashlight Store on ali is sometimes easier and/or may have items that Kaidomain doesn't have in stock...same people. Prices are usually the same when I've looked but with aliexpress sometimes you get faster shipping and maybe a tad easier time with a dispute if something goes south. It's been a long while since I ordered directly from Kaidomain but I've used their LHT ali store several times and it's always been great.
A couple more pics and some thoughts. I think the thermal capacity on this is not terrible. Considering it did 400 lumens, which I believe to be accurate. The star was poorly mounted to the plate. It did not completely fit in it’s hole so was not flat and only had a tiny dab of thermal adhesive. So the thermal path was not good. Also replacing the lens or reflector looks difficult if not impossible. The opening on the bottom of the reflector is 7mm. The gasket top diameter is 6.5mm, bottom diameter 8mm. Height is 2mm with the bottom being 0.5mm and the top 1.5mm.
I also had an idea. I am going to see if I can cut a 2mm thick copper plate to put the star on. It would need to be just shy of 38mm wide to drop in. That would obviously work significantly better than the stock aluminum plate.
Ok, I got it! So the terrible aluminum plate is 3mm. The star is 1.5mm. I found 1.5mm thick copper discs that are 1.5” diameter. So 3mm total. Then I found 1.5” copper washers with .8” holes, which is 20.32mm perfect for a the star to sit in! Stack 2 or 3 of those on, drill holes for the wires and I’ve got a perfect copper plate for my LED! Then just order some different gaskets and test until it all seats right under the reflector.
