Joule Thief 101

[Pirate88179]

Just as I have stated several times.  However, the neutral returns to the transformer center tap via a dedicated wire, not thru the Earth. 

SWER systems in other countries (and parts of Alaska) do use the Earth as a current carrying conductor.

Neither system disproves the existence of electrons...

PW

Sorry, must have missed where you said that.  Yes, of course it does return to the transformer via wire and not the earth.

However, I did read somewhere that the power companies laugh at us because the earth grounds send the energy back to the power plant where they can sell it to us again...being ac.  This made no sense to me but, I am more familiar with dc than I am ac.

Bill

[TinselKoala]

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.

Yes, always (or at least whenever possible). You know I don't trust "numbers in boxes" much and prefer to interpret the traces, at least as a cross-check. However the Rigol DS1054z is rather notorious for having some offset on the traces. But comparing the trace value before, and after, the positive pulse seems to indicate the 4mA reading is at least close to accurate.

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

[TinselKoala]

@ 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

I agree.

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]

Actually it's a bit more complicated than that, more of a boost regulator circuit. There are a couple of different 4-lead ICs that are used, as well as the "cob" (chip-on-board) black dot kind.

I have taken apart many of those solar-powered garden lights of many different kinds, and I have yet to find a phototransistor in one. They commonly use a CdS light-dependent resistor (aka LDR or photoresistor) when a separate sensor is used.

YMMV, of course...

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....

Actually the "sensorless" circuit just uses the light level falling on the photovoltaic cell itself, there is no separate or hidden sensor in those.

[TinselKoala]

(snip)

@TK

"FG isolated". Is this via a car battery and inverter running the FG or is the FG output simply going to an isolation transformer?

wattsup

Neither. This FG (MingHo MHS200A) is powered by a wall-wart SMPS with two prongs, so it's not connected to the mains ground wire. Neither the Black (BNC shield) nor Red outputs are connected to the ground. So unless I establish a connection by patching the second channel to the scope or something like that, both outputs are floating. In the present case of course the Black FG lead is connected through the 1R0 current-sense resistor to the scope ground reference. The important point is that the 1R0 isn't shorted out by the connection, since the FG is floating.

[TinselKoala]

TK

Now remove the 1k resistor,and try again.

Brad

Now we get into the meat of the matter.   

When the 1K resistor across the LED is removed, the LED goes out.

But when I replace the resistor with a 2.2 uH inductor (DC resistance about 0.8 ohm) , the LED comes back on.