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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In an email, Kirk said that he has found that ‘dead’ laptop batteries often have only a single cell that’s bad. I have torn apart some Dell laptop batteries, and found that they have a PC board that has some kind of battery management capability. I also found that the five or six cells
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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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I originated this in SwitcherCAD III back inApril of 2004, and posted it to my late watsonseblog. The one on the right seems to be more commonly used.
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 commented on a Youtube video and the author replied he found that he could get PC Boards made for cheap from Futurlec.com. I looked at their FAQ and found that they will accept designs made in ExpressPCB, which is what I use. Their cost estimator said I can get the same boards for 44
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This is a continuation of the earlier blog. I wanted to change two parameters, the flash rate and the peak LED current. To do these, I experimented with the following. Flash Rate I built a sixth one (or seventh – I’m beginning to lose track, even though I labeled them). I changed the C1 capacitor
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