Modifying a Dorcy spotlight

[PCC]

Here's a little project that I've started and hope to finish in the next day or so. It's an inexpensive Dorcy spotlight that runs on a 6V lantern battery. The PR flange bulb that is in it is terrible. It's not very bright even with a fresh 6V lantern battery. I changed it to the halogen bulb from my Mag 3D and it was both brighter and the light is whiter, but, being incandescent, it'll drain the battery faster than I want so I decided to convert it to LED with a low budget. How low? Try $0! The LED itself is a Luxeon that I pulled out of my 2D MagLED module when I upgraded the emitter to a SSC P4. I'm going to hook up a small potentiometer that I already had inside the case set to a value that doesn't max out the emitter to extend the life of the battery and to minimize heat build-up from the LED for use during power outages.
Here is the gallery for the pictures. There are a few more pictures than shown here.
Here are a few pictures of the spotlight as it came from the store.

I started by milling a heatsink and mount for the LED out of a piece of scrap 6061 aluminum that I found in the garage. Here are a few pictures of it after the milling operation and test fitting the LED on it with the reflector assembly. Sorry that it is a little rough but it'll be inside the light and no one will see it so it's not a big deal.

I need to mount the emitter to the heatsink and figure out how to do the wiring without shorting the thing out :poof: I'll work on that tomorrow and post more pictures and updates after I some more progress on this. Stay tuned!

 

[kramer5150]

Nice work:thumbsup:

What are the advantages of a pot versus a multi-mode DC-DC driver?

 

[Fallingwater]

What are the advantages of a pot versus a multi-mode DC-DC driver?

Easier and quicker to set up, not to mention much cheaper, but a whole lot less efficient for high-power emitters. However, I understand he wants to set it to the appropriate value for the Lux and leave it like that permanently, effectively using it like a resistor.

Personally I'm an efficiency junkie, so I wouldn't use Luxeons for anything that has to run on batteries. If I had any lying around (which I don't, fortunately) I'd use them in fixed installations.

 

[PCC]

I wanted to complete this with as little money outlay as possible. I really didn't want to try turning a sow's ear into a silk purse, so to speak.

Well, I wired it up today. I had marked what I thought was the anode side but blew it so the first time I hit the button nothing happened. I double-checked my work and everything was working properly so I placed the battery on the contacts in such a way that it was reversed and the LED lit right up. :ohgeez:Took it apart and redid it correctly and the second time it worked out. I then tried to adjust the value on the potentiometer and soon found that it was bad. It was working initially but after a while I was not getting anything past the pot so I replaced it with another one I had. Turns out that one was bad, too (could not be adjusted no matter how much I turned the adjuster). Dug up a 16 ohm resistor I had laying around and put that in instead. Works like a charm! According to the resistor calculator I used this should give me around 200 ma to the Luxeon. I might substitute a resistor with a lower value to increase the current but this isn't bad, so far. I think 8 ohms will do it for 400 ma but run times will suffer. I ran it for a half hour straight and the heatsink didn't even get warm to the touch.

It works fairly well other than that I didn't get the focus quite right and instead of a nice small spot I get a slightly larger spot with some artifacts and rings. Oh, well, at least it's a smaller hotspot than my MagLites and the hotspot is pretty much round, not oblong or funny shaped indicating that I didn't center the emitter.

This little light is going to be my power outage light to be used around the house so I don't really need a lot of light but I do need a nice, long runtime and I think this will meet that goal.

Here are more pictures. Sorry, I didn't take a before beam shots so I won't take an after one unless someone wants to see it.

 

[Fallingwater]

200mA? C'mon, you might as well be using 5mm LEDs :p crank that Luxeon up!

 

[PCC]

Actually, I was just thinking of mounting a switch inside with both the 16 ohm and an 8 ohm resistor so that I can select two different outputs. It's still a work in progress.

Last night I cut an old credit card up to make a shim to place between the heatsink and the reflector. This tightened and cleaned up the hotspot nicely, though I can probably fine-tune it some to get the spot even tighter. It's not super tight but it's not bad. I'm more than happy with the way this turned out so far so I can stop working on it and still be happy with it. Not bad for a $5 total investment, eh?