There seem to be a zillion pitfalls out there just waiting to entrap the unwary buyer. Take for instance my dilemma. The bozo at work borrowed the Brother P-Touch labeler and brought it back without the AC adapter – apparently he lost it. So we put eight AA cells in the battery holder and it
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I had a Joule Thief already assembled, using point-to-point wiring. The transistor was a BC338. The coil was a 3/8″ (9mm) toroid core with a primary winding of about 20 turns of 26 AWG and 666 uH, and a feedback winding of 190 uH. The resistor was 1000 ohms. Modifications I disconnected the feedback (base)
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This is the second one I’ve built. The first one I built is in my earlier blog – links to the schematic can be found there. I used the following parts: a 2N3906 for Q1, and PN2222A for both Q2 and Q3. R1 was 470 ohms, R2 was 10k and R3 was 8.2k. Both the
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I’ve blogged this project more than once in the past, (and here too), but I didn’t follow through with the circuit completed and installed in a DMM. Well, I finally got my act together and on the road, and finished the first working 1.5V to 9V DMM power supply. I thought about it and concluded
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I built this up to see how well the blue LEDs I got recently would work on the DC output of a JT. I put three pairs of two in series on a perf board and soldered them to the air wired JT. I knew that the Vf of two blue LEDs was going to
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I built this 1.5V to 9V DC-DC converter. It’s a modified Tim Williams design. It’s a Joule Thief with the output rectified and filtered, which is compared to the “Vref” zener diode and if the output voltage is too high, it turns off the base bias current to the Q2 driver transistor. The input is
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I drew this schematic almost ten years ago, and of course the actual charger is nowhere to be found. I think it may have burned out somehow, and that was why I drew the schematic. Whatever the case, it does have current limiting, which has to be in anything like this that might be used
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I finished gluing the 10 000 uF capacitors down to a piece of wood. I now have a Massively Parallel Capacitor Array (MPCA) Now the hard part comes: connecting all 150 of them up in parallel. I bought a whole box of 250 electrolytic capacitors on tape and fan folded. They were only ten dollars
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DMMs All Over The Place – I have more than a half dozen of those cheapo Cen-Tech DMMs from Harbor Freight laying around my house, and I use them a lot for checking the AA and AAA cells that I’m constantly trying to drain with my germanium Joule Thiefs with their multicolored LEDs, of which
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Question Of The Month: Every duplex electrical outlet should come with a 5V USB charging port built into the outlet next to the sockets. [ ] I agree [ ] I disagree Well, I’m afraid that someone has already thought of that*. I was in the Big Box home improvement store this weekend and they’re
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