In my extensive peregrinations around the Wired Weird World looking for answers to the puzzles that LED lighting present, I came across a website selling LED torch light bulbs for 190 yen apiece. Never wise enough to resist wasting money on a bargain, I put in an order for four of these. Two rated at 3-5 volts and two at 4.5. I've now opened two of them, and one is a little brighter than the other, but they are identical so I'm not sure which one was which.
The immediate use is a series of battery-powered camping lamps that are in that grey area between the store room and the dustbin. LEDs for camping is an obvious choice, especially if you have small children, who are likely to switch the light on as soon as it gets slightly dark, and leave it somewhere until the morning. A conventional bulb will leave the batteries flat in no time. Since we started using LEDs for camping, we found that the batteries were still working when we got out the camping gear the following year. Another advantage of LEDs when camping is that they don't attract insects.
So, rather than throwing away the old camping lamps, replacing the bulbs with LEDs seemed like a sensible option. This is no doubt a false economy, but there it is.
We have three old-style lamps, with a handle that turns into a stand and allows the lamp to point in any direction. Two were large and one was a miniature version, that takes double-A batteries. The only batteries I had were double A's, so that was the one to be tested. I think this was a Thursday morning, but work seemed much less important than trying out these new devices.
The bulb fit the torch well enough, and the light came on. I had checked the diameter, and it was an E10. The 10 means 10mm, and I'm not sure what the E means, but I also got some E17s for some small table lamps and clip-on spots, and may get some E27s, which are standard-sized bulbs. They all screw in, which is where things started to screw up.
The problem was the lack of a flange at the top of the metal part of the bulb. The torch was designed for a bulb with no thread, but a flange at the top. This was held into place by a metal ring that screwed onto the plastic bulb holder, and so kept the bulb in place. I decided a slight modification was in order.
If I bent the metal strip that made the connection to the outer terminal, I thought, that could work on the bulb thread, and keep it in place! Just a little bend one way, then another, and it's sure to hold it in place.
It worked a little, or at least it seemed like it would work if I could bend it the right way. So I tried adjusting it a little more, then a little more, and then the metal strip broke.
The good news was that I now had a small L-shaped strip of metal. I could use this to locate the bulb in the holder, so that the metal ring would now keep it in place and I didn't need to worry about the thread.
The bad news was that the terminal no longer reached the bulb, and the light wouldn't work.
No problem, I assured myself. I can fix that with a little bit of wire from the base of the terminal to the metal ring that is now holding the bulb in place. I got the finest gauge of wire I could find, and made the connections. It looked great, until I tried to switch it off.
The torch switched on and off by sending the bulb holder, with the bulb in it, up and down. This turned it into a spotlight, then a lamp, as the bulb moved up through the reflector. For my modifications of the bulb fitting, I had pushed the bulb holder up, and taken the batteries out to avoid dazzling and a short circuit. After I'd fixed the wire on, I tried to switch the bulb off. This pushed the bulb down into the torch, where a bit of the wire got caught on something, and the switch snapped.
So now the bulb works perfectly, except that it won't switch on.
I was a bit more successful with the other two lamps. I spent another 190 yen on adapters that you can put AA rechargables into, and turn them into big D-sized batteries. The kids can have one big torch each, leave it on for the whole night, and the only thing they can fight over is the colour.
