|The British Caving Association
|LED lighting: how the world has got brighter
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|Author:||David Gibson [ Wed 07 Aug 2013 16:36 ]|
|Post subject:||LED lighting: how the world has got brighter|
If you are my age, you might be able to remember ... just ... the bicycle lamps that were around in the 1960s. The photos below show such a lamp (note the metal construction) and an Ever Ready number 800 battery (photo courtesy of Michael Gerrish). These were discontinued in the very early 1970s but if you ever saw one, you wont forget it - two large zinc canisters in a cardboard wrapper with brass terminals on the top and the side. The cycle lamp had a hole in the bottom to allow you to push the battery up and out of the lamp. The canisters were pure zinc - not plated with steel as they were subsequently - and they were very prone to corroding.
File comment: Cycle Lamp - photo David Gibson
cyclelamp-h200.jpg [ 9.9 KiB | Viewed 3129 times ]
File comment: Every Ready #800 battery - photo Michael Gerrish
battery800_gerrish-h200.jpg [ 10.41 KiB | Viewed 3129 times ]
My thought is that given the lamp characteristics, and the battery data, it should be possible to come up with a numerical comparison between the performance of this bicycle lamp and a modern LED head torch, as found in many retail outlets. You dont even need to go to a caving shop to get a lamp that is perfectly acceptable for caving usage these days, such are the advances in battery and lighting technology over the last few years. Given these advances, just how much "better" is an LED head-torch than a bicycle lamp from the 1960s? Well, if I get around to making the measurements, I'll let you know. I recall that these bicycle lamps were a) not very bright and b) didnt last very long.
The two cells in the #800 battery had, I believe, the Ever Ready part number "60" and were almost exactly the size of today's "F" cells. The 1973 Ever Ready catalogue that I located in my father's garden shed recently doesnt list the #800, which ties in with my memory that it was discontinued in the early 70s, making way for cycle lamps using HP2 batteries (the modern D cell). However the catalogue does list the PJ996 battery, which was constructed out of four #60 cells, and it gives its discharge characteristics. Unfortunately, I cannot find my old "International Lamps" catalogue (I think I must have sent it for recycling, thinking I was never going to need it again) but I have a vague memory that the output of the 2.4V 300mA torch bulb was about 1 lumen. I suppose it would not be too difficult to measure it (shine it on a white surface, photograph it, and crunch the image data in Matlab). So... combining the battery data and some measurements of the lamp brightness will give us the information we need.
|Author:||Rob Gill [ Sat 10 Aug 2013 13:10 ]|
|Post subject:||Re: LED lighting: how the world has got brighter|
This brings back (very) distant memories! My earliest childhood electrical experiments were with my fathers bicycle lamp batteries. It was easy to twist a bit if wire to the terminal strips - though it tested his patience a bit to find the battery either missing or discharged when he needed it!
Another battery I remember playing with, a little later in my evolving interest in such things, was the W9 grid bias battery. This was essentially a tapped row of cells giving 0 to 9V at 1.5V intervals. Interesting to see that one was sold on eBay only very recently. Although sold for display purposes only, I wonder about the condition of the cells since they should have corroded away years ago.
www.ebay.co.uk/itm/Ever-Ready-Battery-W ... 1151024597
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