Joule Thief 101

[TinselKoala]

I don't really trust this scope on very small voltages near the channel baseline so I wouldn't bet the house on that 4mA but it does look like a little bit of current there. Yes, the LED appears well lit. I've already taken the circuit apart but it might be interesting to see the correlation between the LED's actual brightness and the input waveform, by using a photovoltaic cell or phototransistor.

[TinselKoala]

TK

Now remove the 1k resistor,and try again.

Brad

Have to wait until tomorrow, I'm afraid, I've already shut the scope down and taken the circuit apart, sorry. Past my bedtime here....

[picowatt]

I don't really trust this scope on very small voltages near the channel baseline so I wouldn't bet the house on that 4mA but it does look like a little bit of current there. Yes, the LED appears well lit. I've already taken the circuit apart but it might be interesting to see the correlation between the LED's actual brightness and the input waveform, by using a photovoltaic cell or phototransistor.

Having the channel labels immediately to the right of the zero reference marks on the left side of the scope's screen is not that handy either.  It's hard for these old eyes to tell exactly where the zero line is...  but you do appear to be lined up with a major division.

When the waveform is at -6 volts, the three diodes should turn on and conduct with a total of around 1.8-2.1 volts of drop thru all three.

I would think that the remaining 4 volts or so thru the 1K resistor should end up with around 4ma flowing during the negative portion of the applied waveform prior to the rising edge.

PW

[sm0ky2]

@ TK

phototransistor is more accurate, if you can place it in a good spot.
I don't trust PV's for light measurements,
they are consistently inconsistent

luckily for us, both components can be found in many garden solar lights.
along side a superbright, and a charging circuit.
  [note: some Chinese companies hide the charging circuit inside a small black dot of epoxy resin]
          [ it is basically a two or four diode rectifier and sometimes a resistor, that feeds to the battery]

There recently began emerging some fancy cells, that have the sensing unit built into the cell, where you can't even see it, or remove it as a separate piece. From the same Chinese companies....
It seems they don't want us taking them apart and using it for other things....

[picowatt]

  Sorry, hit the wrong key...