I recently came across some of the pictures that I used in early my watsonseblog, sometime around the mid 2000s. From 2000 when white LEDs were very expensive and difficult to obtain, the LED flashlights (torches) were very expensive. Generally, a LED flashlight with a few 5mm white LEDs would cost several tens of dollars
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The LED flashlights I bought in March from Amazon (but shipped from Hong Kong) arrived recently and I’ve had a chance to use them a bit. I paid $5.49 apiece, with free shipping, but I see that the price (as of June 8) has gone down to $4.30, These have a Cree Q5 emitter, and
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This is an old schematic that I drew in Apr of 2005 using SwitcherCAD III (now LTspice). It is taken from the board I built and put in service for several years as a LED test jig for testing the lifetimes of various white LEDs. Needless to say, most of the white LEDs lasted less
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Paul got me thinking about the Joule Thief with low battery current. In his nineteenth JT he used the very high performance Fairchild KSD5041, same as the 2SD5041 (Japanese pinout – the center pin is the collector). He thought it was his brightest, and that could very well be. His theory is that the coil
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(Written by Watson “Watt Sun” Apr 24, ’05 – this was long before you could buy a cheap LED flashlight at the corner store.) When I first started making my white LED flashlights, I made some with four cell battery holders because I couldn’t get any three cell holders. Also I bought several regular 4
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I made this reed relay in May, 2005 and posted it to my late great watsonseblog. I think it hasn’t been posted here yet. It closes at less than a tenth of a volt, which is way too low voltage. This means I need many more turns of much finer wire. But it was difficult
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This Joule Thief uses three SS8050 high current transistors, each having a 333 ohm bias resistor (actually three 1k resistors in parallel). At less than a half volt, it gobbles battery current, 49 mA at 0.42 volts. That is a lot more than the typical JT, which drops to a very low current as the
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This JT uses a larger core that is typically found in low frequency applications such as EMI and RFI suppressors. This toroid has high permeability so it doesn’t take many turns to give a high inductance for a JT. The FT87-75 can be found at Surplus Sales for a dollar or so apiece. The 2SC2500
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When the winding gets tough, double up the number of toroid cores, I say. This JT uses toroid cores that are less than 1/4 inch (6.4mm) outside diameter. The wire has to be fine to get several inches wound on a core. So I wound one core with the wire, and then coupled it to
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Paul suggested this Wikipedia article. I quote: I remembered these, having seen one in action, and always wanted one. I think you might be interested. Perhaps that is why I am interested in JTs. There is more than a simple parallel. http://en.wikipedia.org/wiki/Hydraulic_ram When I was a kid, one of my dad’s customers died and his
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