I've been playing around with a joule thief type circuit to power a higher voltage load, a 3.3 forward voltage LED, with a single AAA battery. A joule thief circuit increases the voltage but this circuit doesn't seem to do so. The circuit did power the LED but on checking the voltage at the positive and negative legs of the LED, I found the voltage to be 1.44 volt for the white LED and 1.33 volt for the green. The LEDs are not supposed to be lit but the two coil sets and the BC 547 transistor worked together to do magic. A 91 ohm resistor is used at one of the coil connection to connect to the positive battery terminal.
With this circuit, I can theoretically use a lower voltage solar panel to charge a set of AA batteries in parallel. The batteries will in turn power my solar light when the photosensor senses darkness. If you want to look at the diagram, just pause your viewer at the point where I show the diagram.
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