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Author Topic: Joule Thief To Amplify Joule Thief?  (Read 5404 times)

Offline Kangsteri

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Re: Joule Thief To Amplify Joule Thief?
« Reply #15 on: March 08, 2023, 02:42:13 PM »
The core is used so you don't need to use that much copper mass. But it will also delay the resonance. I think joule thief might have some true potential, if it's used to light solar panels, like Tritium nuclear battery etc. It's possible to use crystal radio, earth batteries, etc. as source for micro collecting.

Offline sm0ky2

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Re: Joule Thief To Amplify Joule Thief?
« Reply #16 on: March 09, 2023, 04:34:11 PM »
Once again let me apologize if this  has been covered already.  I need your expert opinions. Let us say in a basic joule thief  you have .5 volts input and it lights up a 3 volt LED. Is it possible to replace the LED with ANOTHER joule thief which could then amplify the current to maybe 18 volts?   

The only issue I can think of is that the oscillating  current from the first joule might not be effective to run the 2nd joule  and might mess up the transistor operation in the 2nd joule thief.


First, current is not volts.
Current is amps

Volts are what is stepped up here
Current decreases, as a function of the voltage multiplier

But yes we can, in fact, daisy chain multiple joule thiefs
Secondary transistors are optional, but not required

Offline sm0ky2

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Re: Joule Thief To Amplify Joule Thief?
« Reply #17 on: March 09, 2023, 04:42:53 PM »
A Joule Thief depends on the same principle as boost converters. It uses the collapsing magnetic field of an inductor to increase the voltage over the input, in that way, they are the same.[/font][/size]
Simplifier - Voltage-Regulated Joule Thief (

Do not expect amps from BEMF spikes created by coil with collapsing magnetic field.
It is good to use with "dead" batteries to power LED.

Theres a couple of ways to gain current.
As mentioned above you can use 2 transistors in parallel from the source in a straight forward way
invert one out of phase for a current amplifier

to tap into the current without disrupting the circuit, use a secondary coil (transformer)
 -> diodes to capacitors.

Offline sm0ky2

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Re: Joule Thief To Amplify Joule Thief?
« Reply #18 on: March 09, 2023, 04:48:25 PM »

The usual joule thief is sort of a backward device if you want to increase the power out. Since it’s the magnetic field doing the work the final output should be a greater amperage than given, since the strength of magnetic fields of coils are determined by ampere turns per meter.

Something I try to keep in mind is voltage does not exist in any equation for the strength of magnetic fields of coils. The magnetic field of a coil with 100 A-t at 200 volt and 1 amp is half as strong as a coil with 200 A-t at 0.5 volts and 1 amp.

Yes and no. You are forgetting about the time factor.
There is a current ramp up time
And a current ramp down time
Preceeding and proceeding the current maximum.

It will ultimately follow the characteristics of the transistor
But in a general sense; the current approximates a triangle wave
0 to infinity in 1/2 T then infinity to 0 in the second half
the “average” current is usually what we deal with in a technical sense

Offline sm0ky2

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Re: Joule Thief To Amplify Joule Thief?
« Reply #19 on: March 09, 2023, 04:59:59 PM »
It also depends on where you are measuring
Across the transistor? Or across the coil?
the coil is quadrated, so you have a full wave for current
it actually goes in the other direction during the ‘off’ cycle
some arrangements can take advantage of this
however, keep in mind that the coil currents are much smaller magnitude
than the transistor current.

It is best practice to measure the transistor separately
And compare power measurements.

As voltage is also different on the other side
(negative voltages on the coil during the ‘off’ cycle  as well)

some very interesting things happen when we begin to siphon off and store the electricity
we think we know whats in the batteries, dead as they may be
and the earth batteries, small solar cells etc have been tested to exhaustion

yet a tiny JT can still cause explosions and burn up wires