Reverse Engineering: Solar Lantern Circuit Part II
So now we need to know what the inductor is and what the diodes are. The only definitive way to determine what the diodes are - is to unsolder them and read the labels.
So D1 is the plastic-y one and it has 1N5817. And the glass diode is D2 - 1N4148. Annoyingly, depending on how you look at it, it also looks like 1N4146.
The inductor is a bit harder to figure out, honestly. I'd get an inductance meter if you can, but if you can't and want to be masochistic...the way we essentially did it (thanks to @mgburr and @apexys) is by finding the resonant frequency that the inductor works at.
So we tried a Clapps oscillator:
Which didn't give me much of anything. The line on the scope moved upwards, but I didn't see any waveform.
So then Apexys suggested a 555 wave generating circuit. To be honest, I'm not completely certain what it does. But what I did was once the circuit was made, I tapped my scope's probe off of pin 7 and got a rough estimate of the frequency of the wave.
Note, the chip did get hot to the touch with this circuit, even though it worked.
Waveform on scope:
And we estimated a frequency of 15-18kHz for the triangle-ish pulse. Based on that estimation and the tank circuit equation.
For 15kHz, the inductor would be 1.125 mH
For 18kHz, the inductor would be 0.7818 mH
But wait....it seems like the actual frequency that we want is actually hidden in the waves inside of the triangle shape there. So......per Apexys, the frequency is much higher than 15-18kHz.
@_@ *googles for inductance meter*
@atdiy/@tymkrs
