Is joule thief circuit gets overunity?

[Pirate88179]

That's an interesting idea. The coil windings will probably induce eddy currents in the metal casing of the batteries, which will probably reduce the self inductance of the windings, but it will be interesting to see what results this produces. Also, winding around the super cap should be interesting as well. Good idea! I will give this a try when I get a chance.

So will I.  Thanks TK.

Bill

[Void]

@Lawrence: I was going to do some measurements on your boards using your method to connect the scope probes for the input voltage and current measurements, but I believe there is a problem with this method of measuring the input waveforms. When the scope probes are connected in the way you are doing it for the input waveform measurements, what you are measuring as Vin is actually not Vin, but actually Vin minus the voltage across the 1 ohm current sense series resistor. Although the voltage across the series resistor is not really high compared to the input voltage, based on my measurements it will make the input voltage measurement vary by about 4% or so. Since the accuracy of the scope itself when measuring such lower amplitude voltages is probably already not really great, adding an additional variation of about 4% to the input voltage measurements is probably too much error.

On another note, something odd I have been noticing recently:
I have been conducting a few tests with the JT circuits over the last few days, and something odd I have noticed in measurements with both your JT board #119 and my JT circuit is that sometimes I am measuring a somewhat higher efficiency on these JT boards than other times. (From tests so far, this variation seems to be on top of the difference in efficiency that I measured when comparing efficiency between a regulated DC supply and a super cap as power input sources, but I still need to run more tests to confirm that). I will run some tests on my scope to try to determine if my scope or probes could be having issues. I don't think my scope or probes are having issues, however I won't know for sure until I run some measurement tests with my scope. If the issue is not with my scope or probes, then I can't see why the efficiency of the JT boards could change every now and then. I am talking about differences in measured efficiency of 5% to 10% or so. The actual voltage and current waveform traces on the scope reflect these measured changes, so it doesn't appear to be a problem with the scope data logging. I know bad connections on the boards could also potentially cause something like this, but so far I have seen this variation on both my circuit and on Lawrence's board 119 which is soldered. I will check out the boards as well to see if I can rule out potential bad connections. Lawrence I won't post up any more measurements until I get a chance to investigate these odd measurement variations more carefully. Hope it's not an issue with my scope... 

Edit: The reason I think it is not an issue with my scope is because when I connect the Ch1 and Ch2 scope probes up to the scope's reference 1kHZ squarewave terminal, everything looks fine.

[Void]

<deleted - poynt99 has already answered my question>

[poynt99]

Void,

Yes, this is the way Lawrence and I measured his input power.

I already pointed out this issue some time ago in this thread, and Lawrence simply compensates for the CSR in the spreadsheet calculations. It makes the input power appear to be a little lower than it actually is.

There is no need to worry however, as all measurements have shown far less than unity, even without compensating for the CSR error.

The way you are measuring the LED power, you have the same problem there too.

[poynt99]

Here is where I made that post:
http://www.overunity.com/12686/is-joule-thief-circuit-gets-overunity/msg356492/#msg356492

Void, Why are you OK with your Pout measurement when the very same issue is present?