Joule Thief

[gadgetmall]

@ ALL

   HAPPY  EARTH DAY

Gadget

[Mk1]

@all

Great earth day!

Mark

[jadaro2600]

@ jadaro2600

Yes. So what. You seem to be missing the point. Which is:

If you have a high voltage on the collector coil it will zap the transistor. You do not say, but I am sure that the voltage on the 150 turn coil when used as a pickup coil is much higher than the voltage on the 12 turn collector coil when used as part of the JT. Measure them and tell me what the voltages are. The point is that using a pickup coil allows you to get high voltage without zapping the transistor. You seem to have some sort of mental block about this.

The pickup coil can also be used to get higher currents if it has fewer turns than the collector coil. More turns than collector coil yields higher voltage than collector coil, fewer turns yields higher current than collector coil.

Now that I'm aware of my mental deficiencies, and my mental block. All that I can do is reiterate.

There is a limit to what can be done with a 1.5v source.  You don't zap the transistor if you give it somewhere else to go when the transistor is off.

The only time that the voltage occurs is when the transistor shuts off and the magnetic field collapses.  This causes voltage in a secondary as well.  Meanwhile, however, there is induction in the secondary, and the current momentarily reverses prior to this large voltage spike.

Excuse my deviations from the secondary trend, but, isn't it prudent to realize that if there is a large voltage in the collector coil, as well as an available current equal to that of the source battery, then the circuit potential (as in available energy for use on a load) across the collector coil through to ground ( not through the transistor ) is higher than there would be for any proximally located secondary coils?

Everything coming off the emitter is wasted in the process of creating oscillations.  Perhaps someone with an oscilloscope can confirm my hypothesis that energy coming from the emitter is pulsed?  This would mean putting the probes between the positive pole of the battery and the emitter on a setup where there is a scondary? ...or am I yet again suffering from a mental block?

[jadaro2600]

Why are we aiming for high frequency?

Doesn't it make sense that the higher the frequency, the closer to continuous something becomes?

In order to fully harness the power of a collapsing magnetic field, the best frequency will depend on the induction, core permeability and capacitance of the path, material and the circuit respectively.

[TheNOP]

The only time that the voltage occurs is when the transistor shuts off and the magnetic field collapses.  This causes voltage in a secondary as well.  Meanwhile, however, there is induction in the secondary, and the current momentarily reverses prior to this large voltage spike.

wrong.
you are forgetting inrush currents.
and the small reverse voltage is caused by the base coil.

Everything coming off the emitter is wasted in the process of creating oscillations.

?
it is not waisted, why are you saying that ?


simple faqs :
switches give us inrush currents at closure time.
we also have a coil, that give us voltage spikes when the switch open.
yes, there are 2 distinctive kicks in a jt, both of same polarity, same as the initial currents flow.

if you are to add more resistance, ex: a load, between either side of the transistor and the battery, you will minimise inrush currents.