Is joule thief circuit gets overunity?

[poynt99]

Hi Poynt99. Ok on that.  I wonder if Lawrence has ever run the self-calibration routines on his Atten scopes?

That's an unknown.

However, I would think that if the current waveform is inverted it will give errors in the instantaneous power calculations, as many of the input current waveform data points will be recorded as negative when they are actually positive. This would make the instantaneous power calculations and average power calculation invalid, no?

It's not a problem. The only affect would be a reverse in polarity. The magnitude is most important, and it would remain intact.

[Void]

Not a problem. The only affect would be a reverse in polarity. The magnitude is most important, and it would remain intact.

OK, thanks for the clarification. Lawrence is planning on sending me a couple of his boards for testing so we can compare my measurement results to his measurement results on those boards and see if there is a difference.

@Lawrence, based on the offset issue that Poynt99 suspects with your scope, I think that it would be a good idea to run the self-calibration routines on your Atten scopes if you have not done this previously. This could potentially correct any offset error in your scopes if there is some.

[Void]

@Tinselkoala, Ok, on that. If Lawrence has not run the self calibration function on his scopes recently, then I will see if Lawrence is willing to do this and then re-do his measurements on his two boards before he sends them to me. The self-calibration may help correct any offset error his scopes have now.

[ltseung888]

@Tinselkoala, Ok, on that. If Lawrence has not run the self calibration function on his scopes recently, then I will see if Lawrence is willing to do this and then re-do his measurements on his two boards before he sends them to me. The self-calibration may help correct any offset error his scopes have now.

No problem.  I have run the Atten self califbration procedure many times now.  I shall redo it before any serious measurements.
@Poynt99

The Atten is not only showing "cross 0 reference line" that can be explained by DC Offset.  It is also showing the voltage spikes crossing the 0 reference line.  When that happens, the LED can be ON for days (Board 116 lasted for 3 days at 0.352V).  I shall try to repeat it for Board 118 and 119.

[Void]

No problem.  I have run the Atten self califbration procedure many times now.  I shall redo it before any serious measurements.
@Poynt99

The Atten is not only showing "cross 0 reference line" that can be explained by DC Offset.  It is also showing the voltage spikes crossing the 0 reference line.  When that happens, the LED can be ON for days (Board 116 lasted for 3 days at 0.352V).  I shall try to repeat it for Board 118 and 119.

Thanks Lawrence. I actually have two DSO scopes. A 50MHz Hantek USB peripheral plug in type scope, which is what I  used on my previous tests on my joule thief circuit here, and a 100MHz Siglent 1102CNL scope, which is what I am going to use to run tests on your boards, since the Siglent should be a better scope overall, and it can be set down to 2mV/div, whereas my Hantek can only be set down to 10mV/div.

I did some testing with my Siglent scope yesterday. I warmed up my scope for 20 minutes and then configured each probe/channel to DC, x1, and 2mV/div, and then grounded the probe tips to their ground clips. There was some DC offset showing on each channel, so I ran the self-calibration function on my scope. (My Hantek scope instructs connecting the scope probe tips to the ground lug on my scope when running the self-calibration, but my Siglent scope instructs to disconnect the probes from the scope when running the self-calibration). With the scope probes again connected to the scope, I then double checked that each probe/channel was still configured for DC, x1, and 2mV/div, and then grounded the probe tips to their ground clips. Channel 1 was showing no offset, but Channel 2 was still showing about + 0.6mV of offset on the 2mV/div setting with the scope tip grounded to its ground clip. I then left my scope turned on overnight and then re-ran the self-calibration function on my scope in the morning, and then rechecked the Channel 1 and Channel 2 DC offsets with the probe tips grounded. Both channels are now showing very close to zero offset (with settings: DC, x1, and 2mV/div). Just wanted to mention this in case it helps with your scopes. I am not sure if leaving the scope to warm up a lot longer helped, or if you just sometimes have to run the self-calibration a few times and keep checking for the least amount of DC offset.

By the way Lawrence, I read that Siglent is actually the manufacturer of Atten scopes, so our scopes should be very similar. The self-calibration method I describe above should be very similar if not exactly the same for your Atten scopes. What model of Atten scopes do you have?