|One or Four LED Flashlight|
What if you want a flashlight that has everything – a dim light that will last a long time to see around your tent or read and a bright light for those times you need to see better? This is my idea of the ultimate flashlight. The circuit below does just that. The LED specification calls for 3.6 volts and .02 amps. The two sets of two LEDs and 90-ohm resistor are in parallel. The single LED uses a 270-ohm resistor.
The cost of the project is about $12 USD. That's about $6 for the LEDs and $3.50 for the case.
You can buy small electronic project boxes 2.4"x1.8"x0.9" to house the whole thing. With a little bit of extra work and materials, you can even turn it into a headlamp.
In testing this light, I ran it continuously on the high setting (all four LEDs on). I compared the light level with my control that was a single LED flashlight with a new battery. After about 18 hours, the four LEDs had dimmed to about the brightness of the control flashlight. After about 36 hours, the flashlight in the four LED setting put out about the same amount of light as when it was in the one LED setting. At 42 hours, the single LED setting was brighter than the four. This is a good indication that you need to change the battery. The LEDs still put out enough light after 7 days for me to easily find my way around the house! It kept burning for over two weeks.
Ready for more fun with LEDs? Try these out: