In 2000 and 2001 the pirate manipulators the likes of Enron drove So Cal Edison and the other electric companies in California to the edge of bankruptcy and caused the electricity shortage, and along with that threats of rolling blackouts. I was concerned about being stuck in some elevator without a flashlight, and since LED flashlights were not yet available, I started building LED flashlights with three AA cells and 6 or more LEDs inside of Altoids tins. A few years later I got hold of several Velamints sampler tins that were just big enough to get a single AA cell holder and small circuit board with three LEDs inside.
The Flashlight I built several of these and have them strategically placed around the house for quick use to see stuff inside drawers, etc. I made a hole for a submini SPST switch and three holes for the Nichia NSPW500BS LEDs, which are connected in parallel. I built the two transistor circuit on a small piece of perfboard and mounted it and the battery holder inside with hot glue.
Circuit Details – (I found an older pic with more info – see below) I used a two transistor circuit with the 2SD965 high current transistor for the LED driver. The black choke with “104” on top is the 100 microhenry choke that boosts the voltage. I bought them for a dollar apiece from Mouser.com – I had not yet started winding my own toroids by then. The other transistor is a BC327-25. There is a 100 pF ceramic disk capacitor to couple the output back to the base of the first transistor, a 100k to minus for the base bias to the first transistor, and 47 ohm and 820 ohm resistors. At that time, the white LEDs were selling for $4.00 to $5.00 apiece at Radio Shack, so I soon ordered a hundred from Nichia at half that price, $2.00, and later a bit cheaper.
During the early 2000s the only white LEDs available were the 5mm that could handle 1/10 of a watt. To make a bright flashlight, it took a half dozen or more to get a decent beam of light. During the mid to late 2000s, the prices of LEDs began to drop, and the makers came out with the higher power white LEDs, the 10mm and strawhat types that could handle a half watt or a watt or more. Flashlight makers started to make decent little flashlights that used a single half watt or 1 watt white LED with a reflector, and a circuit to boost the 1.5 volts to that needed for the LED. I don’t carry my homemade flashlights any more, I carry a Fenix LD01 0n my keychain, and it puts out an unbelievable amount of light for its small size.
Back to experimenting…