Is joule thief circuit gets overunity?

[ltseung888]

Since the batch of boards from Shenzhen already showed Average Output Power > Average Input Power without the capacitor, I can simplify the demo package.

The capacitor will be an add-on.

In some of of the old boards, I need to add the capacitor to show OU.  In some cases, I need to have the capacitor alone running for some minutes before detecting OU.  Mr. Zhou, as a professional electronics engineer, can do much better soldering work and board arranging.  For the many newbies out there, Your first JT may not show OU.  That is normal.  My first ones did not.  Even now, two thirds of my attempts failed.  If you cannot do it, it does not mean someone else cannot do it.

@TK

Be patient.  Let the Forum Administrators receive and test the boards with their oscilloscopes.  Make sure they have confirmed OU boards in their hands.  Then other tests can happen.  As you already know, not all JT are the same.....

[MileHigh]

Imagine you go to the gym and you find an old-style exercise bicycle.  The type with a seat and pedals and a chain link to a big flywheel, like a regular bicycle.  There is a friction belt that goes around the circumference of the flywheel.  You set the tension on the friction belt to adjust the difficulty level.

Imagine the belt is completely loose.  You pedal for a few seconds and get the flywheel spinning and then you stop pedaling.  Then you add tension to the belt and the flywheel spins down and stops.  Then you loosen the belt and repeat the whole process all over again.

Even when you are completely exhausted, it's still possible for you to pedal and get the flywheel spinning if you pedal slowly and take your time to build up the speed.  Don't forget that the friction strap is loose when you pedal.

That's a Joule Thief.  You are the battery.  The flywheel is the coil.  The friction belt is the LED.

The torque that you put on the flywheel from pedaling is the battery voltage.  The torque that the flywheel puts on the belt during the braking is the coil voltage when it's de-energizing.  The rotational speed of the flywheel is the current through the coil.

I have never heard of any claims of over unity exercise bicycles and by the same token, a Joule Thief - an energizing and de-energizing inductor - is not over unity.

[NickZ]

  Sending those circuits to be tested is a good idea. 
  But, I have been asking for one simple test...  for years now.
  How long will that circuit light a single led using a new 1.5 volt battery? 
  Is this too simple a task. I've mentioned this several times.  I don't care if it takes days, weeks, or even months.
  In any case that will be answered sometime soon, I hope, by the testers that will have those units to work with.  That is the only proof I need, or will accept.

[MileHigh]

It is too simple a task and seeing how long a Joule Thief can light an LED is not a legitimate test.

You are trying to measure the energy output of the Joule Thief and compare it to the available battery energy.  Alternatively you could take a snapshot of the average battery power consumption and compare that to the average output power to the LED.  The second method could be achieved with the careful and expert use of a modern digital storage oscilloscope.

I am sure that there are other ways to do it also.  But the LED test is not one of them.

[conradelektro]

@Kator01 and TinselKoala:

Thank you for showing the issues (stray and non accounted for capacitance) when measuring a HF circuit, I learned a lot.

As NickZ and many others have said over the years, the real test is some sort of self runner. Measurements are of little help in an OU device (in case it really existed) because the OU device would not function according to standard theory and measurements.

Greetings, Conrad