Build a LEDlight
By Bill Jones, KD7S
The ARS Sojourner
It's pretty safe to say that backpackers and hams are gear nuts. If it's smaller, lighter or more powerful, it has to be better than what you already have. That was the case with my backpacking flashlight. My faithful old Duracell 2-cell light worked just fine but it was a little on the heavy side and ate batteries like the Energizer Bunny was my brother-in-law. I wanted something smaller and more efficient.

I spent quite a bit of time cruising around the LED flashlight web page (http://www.uwgb.edu/nevermab/led.htm) looking at all the commercial offerings. While I liked what I saw, I decided I'd rather build my own. (ledlight1.jpg) That way I could include features that I wanted instead of what some manufacturer thought I wanted.

Figure 1 is a schematic of my light. It features a high brightness, orange LED from Radio Shack. In fact, at 12,000 mcd it is the brightest LED I've ever seen. You won't want to look directly into this LED at full power. As a bonus, the orange color preserves your night vision.

The LED is powered by a single CR2450 lithium battery, also available from Radio Shack. The battery is rated at 650 mah. The LED can draw 50 ma. or more with a fresh battery. That was a little higher than I was comfortable with so I included a HIGH/LOW switch. In the LOW position the current drain is more like 20 ma. with a fresh battery. Even on LOW, the LED is very bright. As the battery ages the voltage droops a little and the current consumption becomes downright miserly. I have yet to wear out my first battery and I play with the flashlight constantly.

Because I am comfortable working with tiny bits and pieces of ABS plastic I built my own enclosure. Others may prefer something ready made. Look in your medicine cabinet. A dental floss box should work quite well, and the price is right.

The ON/OFF switch is on the right hand side and the HI/LO switch is on the left. The battery contacts were made from strips of metal robbed from an old telephone type lever switch. If I build another light I would probably use a momentary contact ON/OFF switch instead of the slide switch shown.

The beam from the light is quite narrow and, as I mentioned earlier, very bright. It is perfect for walking around camp in the middle of the night looking for a big tree. It will easily light the trail 20-30 feet ahead. A diffused lens might be a little better for close up work like logging and knob twisting in the tent, but it still works well just as it is. The finished light weighs about two ounces.

This is my first attempt at building a LED flashlight but I doubt it will be my last. I've been playing with different LEDs and battery combinations. The possibilities are endless. So if you're looking for a fun, weekend project, try this one. You'll like it.

Parts List (numbers in parentheses are Radio Shack part numbers)

B1 CR2450 lithium battery (23-189)
D1 1N4001 diode (276-1101A)
D2 Orange, high brightness LED (276-206)
S1,S2 SPDT submini slide switch (275-409A)

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Bill Jones, KD7S, a renowned QRP radio and accessory builder, is a contributing editor to The ARS Sojourner living in Sanger, CA.

kd7s@psnw.com