The LED Megalight

AKA The PVC Tactical Light

Or simply the "Oh my Gawd, my eyes!"

What This Is

This is a homemade LED flashlight with a PVC body that is easily bright enough to blind you, and uses only one special LED (a Luxeon V). The light projected is a smooth, clear white illumination with no "rings" in the projected light like those cast by normal flashlights.

It uses nothing that you can't order from your home or buy off the shelf. The most specialized part is the Luxeon LED itself, and those are available to anyone by mail order from the Lumileds Future E-store at http://www.futureestore.com which ships to US and Canada. Also, they are available from luxeonstar.com which is a Canadian distributor.

It was specifically made as simply as possible (i.e. minimal cutting or drilling) mostly from ordinary PVC parts, a momentary switch, and a cannibalized keychain flashlight. Only one piece of PVC (the tube for the body) needed to be cut. The rest is off-the-shelf PVC couplers or adapters and an end cap.

It has three modes of operation: locked (end cap covers switch, preventing accidental activation), constant on (end cap is tightened down to activate switch), and momentary (end cap is removed to allow momentary operation of switch).

This light is bright enough for tactical use (meaning it is easily bright enough to fully illuminate the immediate area, and bright enough to dazzle or blind someone to gain a tactical advantage) and the same LEDs are in fact used in some real tactical lights - for example, the Streamlight TLR-1 or some by Insight or SureFire such as their X200 series.

What This is Not

It is not optimal in a number of ways. BUT it is a perfectly functional, high-output flashlight. For one thing, it uses a resistor as a current-limiter for powering the LED. Ideally, a battery-friendly constant current power source would be more efficient. However this increases complexity of the design, as well as cost. Nothing beats a simple resistor for combined simplicity, size, cost, and effectiveness.

I don't pretend this could qualify as a tac light; real tactical lights have quality engineered reflectors and optics to ensure wasted light is minimal, and have integrated power management to ensure constant brightness for as long as possible. They are also made to withstand physical mishandling and environmental harshness. None of these is really true for my homemade PVC version, but it *is* perfectly capable and functional and still delivers the same raw power.

The reflector is far from optimal but is much better than nothing. I just used what would fit into the PVC coupler.

Also, it is not exactly pretty - but it has a certain homemade-lightsaber handle look to it. In fact, a clear stick of plastic stuck into the open end would make a dandy lightsaber.

How It Was Made

I will describe the basics of how my light was assembled from the parts I used. But when you make your own, you will need to take some things in your own personal direction from these basics. The reason for this is that I used whatever was at hand, so a complete step-by-step would not be useful to you unless you have the same junk box that I do! But I will explain all the important bits so you can follow the same idea with your own parts. As long as you have the same essential elements, the packaging doesn't matter as much.

In the end, your result might be similar to mine, but will reflect your own personal style. For example, mine turned out to have something of a home-made lightsaber handle look to it. Maybe yours will have this look too, but in your own distinct style.

The Basics

The heart of this is really just the following extremely simple circuit to drive the LED. If you know enough about electronics, you can use the datasheets or application notes from Luxeon to make your modifications.

I used the LXHL-LW6C which is a Luxeon V STAR (comes with a built-on heatsink), and my power source was 3x CR123A batteries (each being 3V, for a total of 9V).

(Click for larger versions)

NOTES

• The batteries make 9V total but there is more to it than that. Your usual rectangular 9V battery will not work as a substitute, as the common rectangular 9V actually contains a relatively small amount of energy and will not cough up the kind of current we need. If you must use something other than three CR123A batteries, use 6 AA (or C, or D) cells instead. Don't use a higher voltage without re-calculating the resistor value (see the Luxeon Resistor Calculator for help with that if you need it.)

• The resistor is NOT OPTIONAL in this design. Don't leave it out. There seems to be a trend towards people omitting current-limiting resistors when making LED light projects. Sometimes it's by design but it usually seems to be out of ignorance. Never connect an LED to a voltage source without an appropriate resistor to limit the current unless you know precisely what you are doing.

• Using a resistor is not the best way to get the most out of your batteries, but it works and it's impossible to undercut the the humble resistor's low cost and small size in this application. If you do want to take the power supply to the next step, you should use a constant-current source to feed the desired current (700mA max) to the LED. See Luxeon's application notes for their LEDs for specific details. You will need electronics knowledge to go that route. One way to go about this is to get the Power Puck from Luxeonstar.com or some other distributor. They are made specifically for driving LEDs such as the Luxeons with constant current from (for example) batteries.

Construction

Remember - this is just how I made mine. You should make your own up using your your junk box and parts. As long as you have the right circuit, you will be fine.

Here are some useful tidbits I discovered along the way:

1. 3/4" inside diameter tubing is wide enough to hold CR123A batteries, with room for a wire running alongside.

2. You can find some useful parts by cannibalizing a cheap flashlight.

3. There is more than one way to skin a cat. You could easily combine almost any number of couplers or ends to get a different look.

The parts I used: Luxeon LED, 1$ keychain flashlight, momentary switch, batteries, resistor, and PVC parts.

I soldered the resistor directly to the LED base, making sure not to create a short to the heatsink.

The LED assembly fits nicely perched on this piece. The short tube with the reflector will screw down onto this.

The bottom end of the keychain flashlight (with spring inside) is used to house the momentary switch as well as the spring contact to the (-) of the batteries. The only piece of PVC I have cut is the grey main tube, which holds the batteries. The switch end is held in by friction thanks to adding a little tape. To replace the batteries I would pull this end out (there is some slack in the wire allowing it to be pulled out).

The final piece is the short tube that houses the reflector scavenged from the keychain flashlight. Some aluminum tape has been added to the inside of the tube, too. Silicone glues the reflector in place, and the whole thing will screw down over top of the LED. (Note that reflectors made specifically for the Luxeons are available from luxeonstar.com and possibly from elsewhere as well.)

• Screwing the end cap on partway will prevent the switch from being accidentally triggered.

• Screwing it down further will push the switch down so the flashlight is constantly on.

• Removing the end cap completely will allow momentary activation of the light by pressing the momentary switch.

The Finished Light!

If you look closely at the next picture -- see that yellowish square visible in the reflector?

That's the light emitting part of the Luxeon V LED. That's the piece that's normally around a millimeter big on a normal LED. Small wonder this one is so bright!

Other Possibilities

Such a tiny and POWERFUL light source can be useful for many things. For example, notice how my PVC light ended up having a lightsaber-handle look to it? And notice how the top part with the reflector screws off? A 1" diameter clear plastic or acrylic bar inserted into that piece would make a nice lightsaber blade, and it would light up quite brilliantly I assure you - and the Luxeons come in colors other than white. I'm actually not that big of a Star Wars fan, but the possibility is not hard to see and it would be easier than soldering up strings of normal LEDs. These things are great!