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I've found another one, rooting around through. It was intended as a micro-HV supply (for the electronic flash on a Kodak disposable camera); as such, it generated 350 volts from a 1.5V AA cell. (Circuit here). But Sam G. adapted it for lower-voltage duty, apparently by rewinding the original transformer. (Interesting discussion on that page about the operation of this circuit.)
Here's my drawing of it:
The thing is so dang simple that I just had to try it. So I did. I wound a little transformer on a small (1/2" or so) ferrite bead with some of my salvaged magnet wire. Dang if I didn't get a good solid 6 volts at about 25mA out of it!
I think this is actually a good candidate to run little 5-volt powered projects from a single AA cell. Of course, one would want to add a regulator (maybe just a 5V zener to keep it simple), since the voltage will go waaaaaaay up under a smaller load (I used a 220Ω resistor as a dummy load; haven't yet measured the no-load voltage, but I'm sure it's much higher).
Looking at this circuit, it's something of a mystery how it operates. My problem is with finding the return path to the positive side of the supply: it can't be through that little 470pF cap, can it? or through that rather large resistor?
I'm going to try to model this with LTspice, but simulating that transformer is going to be tricky. Wonder what frequency this runs at?
Here's my drawing of it:
The thing is so dang simple that I just had to try it. So I did. I wound a little transformer on a small (1/2" or so) ferrite bead with some of my salvaged magnet wire. Dang if I didn't get a good solid 6 volts at about 25mA out of it!
I think this is actually a good candidate to run little 5-volt powered projects from a single AA cell. Of course, one would want to add a regulator (maybe just a 5V zener to keep it simple), since the voltage will go waaaaaaay up under a smaller load (I used a 220Ω resistor as a dummy load; haven't yet measured the no-load voltage, but I'm sure it's much higher).
Looking at this circuit, it's something of a mystery how it operates. My problem is with finding the return path to the positive side of the supply: it can't be through that little 470pF cap, can it? or through that rather large resistor?
I'm going to try to model this with LTspice, but simulating that transformer is going to be tricky. Wonder what frequency this runs at?
