Request for Design Review Comments

Here's a drawing of a design idea I've been working on.

Go here:
http://edusite10.tripod.com/led3/smount/smount.htm
and click on the link called:
Prototype Flashlight Adapter Configuration

I started with a 2AA Ray-o-Vac Industrial flashlight because it has a tailcap and a battery stop on the positive end, and wondered if I could make it into a homemade Arc LS but with a dimmer.

I'd appreciate any comments to improve it. It's still all on paper so changes are no problem.

Hi Jeff.
It looks like your LED mod is going to double the size and weight of the torch. Why not use a larger torch (preferrably metal) so that all the guts fit inside?
There's no reason why it shouldn't work though, and you've made provision for cooling your luxeon.

I'm not sure what the battery stop is for, wouldn't the batteries be loaded from the tail end of the flashlight, so wouldn't it be stopped by the circuit board?
And instead of mounting an adapter to the head of the flashlight, what about just lengthening the pipe and using that as the body? I think if you had a metal body, you wouldn't need to drill holes in the flashlight for ventilation. Do you plan on overdriving the LS a lot, so you need more cooling?

On second thought, if you were going to go through all that trouble, it probably would be easier to start with an all metal flaslight to begin with. Maybe a 2C mag light, and if you reall wanted a tailcap switch, just drill a hole in the tailcap and mount a switch in there. Then you could use the original switch location to hold your dimmer control

I thought about using a 2C Maglight but, ahh, I don't know, I need more freedom to express myself.

I'd like to use thin wall plastic tube because its so workable, but metal tube might be better for heat transfer, but then again, for metal tube the heat path to the outside is long and it might take a lot of dT to push the heat all the way out to the outside from the center of the LS. And with metal tube, there's the issue of thermal contact between the aluminum disk and the tube.

If that's the case then the effectiveness of the metal tube might be low, so might as well use plastic with a good internal heat sink and a couple of vent holes.

I wonder how important thickness is for the aluminum disk under the LS. I could use 1/8" thick aluminum flat bar. That sounds about right and it's easy to come by.

I also have kind of an antique 2C Rayovac metal flashlight. If I can make an extension cylinder like this, and keep it short, maybe I can make it clip onto that light too. Then I can have dual battery capability.

Like someone around here once said, "I don't want to end up with a brick."

But I sure do like the dimmer.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:

1. I'm not sure what the battery stop is for

2. Do you plan on overdriving the LS a lot, so you need more cooling?

3. Then you could use the original switch location to hold your dimmer control<HR></BLOCKQUOTE>

1. The rayovac light has a T1 bulb instead of a PR bulb. When the lens assembly is removed, the batteries don't fall out the top. I want to be able to load batteries from the tail end so all the junk in the front end doesn't have to be disturbed.

2. 350 mA is plenty. How much current can I push through without any heat sink?

3. That's a good idea. The dimmer switch also has an on-off switch built in to it.

4. Kind of sounds like I'm heading in the metal tube direction doesn't it. Gotta think a little more about methods for attaching it. Darn, glue and plastic get along so well.

I don't know how much current you can push through the LS/o without any heatsink but I don't think it will be anywhere near 350 ma. Running the LS/o at factory specs was intended to be with a secondary heatsink (according to the spec sheet that came with it).

Jeff1500,
the metal flashlight body would be the easiest and best way to make this flashlight. The distance the heat has to travel to reach the body is not really that important as long as the contact is good between the heatsink and the body. If you have a plastic body with an internal heatsink, no matter how big of a heatsink you have, that heat still has to be transferred to the outside somehow, so eventually you'll still need to use the body as some sort of heatsink. Even if you drill holes in the body, it's not going to help that much with the heat transfer, unless you plan on using this only in a cold, windy, or possibly an underwater environment. The amount of air convection through the holes isn't going to help a whole lot.

Okay, now for the important information. If you're anything like me, you don't want to take the easy route, you want something that is completely handmade. Then your design should work fine, IF you're not going to overdrive the LS, and IF you have an internal heatsink. You probably think I'm an idiot because I just said that even with an internal heatsink you'd still need to transfer the heat outside. Well, that's still true, but since we're talking about a low power device, it shouldn't be much of a problem. The internal heatsink will keep the LS from overheating, and the power dissapation would be so small that you probably wouldn't need to worry about it. I don't think you'd even have to drill holes in the body of the flashlight, like I said, it's not going to make that much of a difference anyway.

So if you're looking to make a simple, effective conversion, use a Mag body. Physical contact with a metal body is by far the best way to transfer heat. If you really like the plastic flashlight idea, you're design should work fine. But I still don't understand why you need a battery stop. Even if you had a simple tube, wouldn't the circuit be attached on one end of it preventing the batteries from falling out anyway? Then you could just get a piece of pipe, glue the whole circuit/LS/heatsink thingy on one end, the get an end cap and drill a hole in it for the tailcap switch on the other end.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by InTheDark:

1. The amount of air convection through the holes isn't going to help a whole lot.

2. I still don't understand why you need a battery stop. Even if you had a simple tube, wouldn't the circuit be attached on one end of it preventing the batteries from falling out anyway?

3. If you're anything like me, you don't want to take the easy route, you want something that is completely handmade. <HR></BLOCKQUOTE>

1. That sounds right. As I think about it, the metal body looks like by far the best way to go with a 1/8" thick aluminum disk under the LS in contact with the metal tube.

2. The circuit board could certainly be the battery stop. I liked the rayovac light because it has a tail cap for easy battery removal. It's also convenient that the lens end is almost exactly 1-1/2" which is the same outside diameter as the chrome sink drain tube.

3. I'm like that. For me it's the journey, not so much the destination.