Joule Thief 101

[MileHigh]

http://makezine.com/projects/joule-thief-battery-charger/

How a Joule Thief works:

This circuit used in this project is a modified "Joule Thief." A Joule Thief is a self-oscillating voltage booster. It takes a steady low voltage signal and converts it into a series of high frequency pulses at a higher voltage. Here is how a basic Joule Thief works, step by step:
    1. Initially the transistor is off.
    2. A small amount of electricity goes through the resistor and the first coil to the base of the transistor. This partially opens up the collector-emitter channel. Electricity is now able to travel through the second coil and through the collector-emitter channel of the transistor.
    3. The increasing amount of electricity through the second coil generates a magnetic field that induces a greater amount of electricity in the first coil.
    4. The induced electricity in the first coil goes into the base of the transistor and opens up the collector-emitter channel even more. This lets even more electricity travel through the second coil and through the collector-emitter channel of the transistor.
    5. Steps 3 and 4 repeat in a feedback loop until the base of the transistor is saturated and the collector-emitter channel is fully open. The electricity traveling through the second coil and through the transistor are now at a maximum. There is a lot of energy built up in the magnetic field of the second coil.
    6. Since the electricity in the second coil is no longer increasing, it stops inducing electricity in the first coil. This causes less electricity to go into the base of the transistor.
    7. With less electricity going into the base of the transistor, the collector-emitter channel begins to close. This allows less electricity to travel through the second coil.
    8. A drop in the amount of electricity in the second coil induces a negative amount of electricity in the first coil. This causes even less electricity to go into the base of the transistor.
    9. Steps 7 and 8 repeat in a feedback loop until there is almost no electricity going through the transistor.
    10. Part of the energy that was stored in the magnetic field of the second coil has drained out. However there is still a lot of energy stored up. This energy needs to go somewhere. This causes the voltage at the output of the coil to spike.
    11. The built up electricity can't go through the transistor, so it has to go through the load (usually an LED). The voltage at the output of the coil builds up until it reaches a voltage where is can go through the load and be dissipated.
    12. The built up energy goes through the load in a big spike. Once the energy is dissipated, the circuit is effectively reset and starts the whole process all over again. In a typical Joule Thief circuit this process happens 50,000 times per second.

What the heck?   No mention of "resonance" anywhere?!  No mention of "LC" or "RLC" anywhere?!

It must be an NWO plot and they want to hide the truth from you.

[Pirate88179]

http://makezine.com/projects/joule-thief-battery-charger/

How a Joule Thief works:

This circuit used in this project is a modified "Joule Thief." A Joule Thief is a self-oscillating voltage booster. It takes a steady low voltage signal and converts it into a series of high frequency pulses at a higher voltage. Here is how a basic Joule Thief works, step by step:
    1. Initially the transistor is off.
    2. A small amount of electricity goes through the resistor and the first coil to the base of the transistor. This partially opens up the collector-emitter channel. Electricity is now able to travel through the second coil and through the collector-emitter channel of the transistor.
    3. The increasing amount of electricity through the second coil generates a magnetic field that induces a greater amount of electricity in the first coil.
    4. The induced electricity in the first coil goes into the base of the transistor and opens up the collector-emitter channel even more. This lets even more electricity travel through the second coil and through the collector-emitter channel of the transistor.
    5. Steps 3 and 4 repeat in a feedback loop until the base of the transistor is saturated and the collector-emitter channel is fully open. The electricity traveling through the second coil and through the transistor are now at a maximum. There is a lot of energy built up in the magnetic field of the second coil.
    6. Since the electricity in the second coil is no longer increasing, it stops inducing electricity in the first coil. This causes less electricity to go into the base of the transistor.
    7. With less electricity going into the base of the transistor, the collector-emitter channel begins to close. This allows less electricity to travel through the second coil.
    8. A drop in the amount of electricity in the second coil induces a negative amount of electricity in the first coil. This causes even less electricity to go into the base of the transistor.
    9. Steps 7 and 8 repeat in a feedback loop until there is almost no electricity going through the transistor.
    10. Part of the energy that was stored in the magnetic field of the second coil has drained out. However there is still a lot of energy stored up. This energy needs to go somewhere. This causes the voltage at the output of the coil to spike.
    11. The built up electricity can't go through the transistor, so it has to go through the load (usually an LED). The voltage at the output of the coil builds up until it reaches a voltage where is can go through the load and be dissipated.
    12. The built up energy goes through the load in a big spike. Once the energy is dissipated, the circuit is effectively reset and starts the whole process all over again. In a typical Joule Thief circuit this process happens 50,000 times per second.

What the heck?   No mention of "resonance" anywhere?!  No mention of "LC" or "RLC" anywhere?!

It must be an NWO plot and they want to hide the truth from you.

Yes, but Make got the JT design from Big Clive.  (see links in my earlier posting)

Bill

[MileHigh]

http://www.talkingelectronics.com/projects/LEDTorchCircuits/LEDTorchCircuits-P1.html

CIRCUIT A
The first circuit in this discussion is the simplest design.
It consists of a transistor, resistor and transformer, with almost any type of LED. The circuit will drive a red LED, HIGH BRIGHT LED, or white LED.
The circuit produces high voltage pulses of about 40v p-p at a frequency of 200kHz.
Normally you cannot supply a LED with a voltage higher than its characteristic voltage, but if the pulses are very short, the LED will absorb the energy and convert it to light. This is the case with this circuit. The characteristic voltage of the LED we used was very nearly 4v and this means the voltage across it for a very short period of time was 4v. The details of the transformer are shown in the photo. The core was a 2.6mm diameter "slug" 6mm long and the wire was 0.95mm diam. In fact any core could be used and the diameter of the wire is not important. The number of turns are not important however if the secondary winding does not have enough turns, the circuit will not start-up.

HOW THE CIRCUIT WORKS
The transformer is configured as a BLOCKING OSCILLATOR and the cycle starts by the transistor turning on via the 2k7 base resistor.
This causes current to flow in the 60-turn main winding. The other winding is called the feedback winding and is connected so that it produces a voltage to turn the transistor on MORE during this part of the cycle.
This winding should really be called a "feed-forward" winding as the signal it supplies to the transistor is a positive signal to increase the operation of the circuit. This is discussed in more detail in Circuit Tricks.
This voltage allows a higher current to flow in the transistor and it keeps turning on until it is saturated.
At this point the magnetic flux produced by the main winding is a maximum but it is not expanding flux and thus it ceases to produce a voltage in the feedback winding. This causes less current to flow into the base of the transistor and the transistor turns off slightly.
The flux produced by the main winding is now called collapsing flux and it produces a voltage in the feedback winding of opposite polarity. This causes the transistor to turn off and this action occurs until it is completely off.
The magnetic flux continues to collapse and cuts the turns of the main winding to produce a very high voltage of opposite polarity.
However this voltage is prevented from rising to a high value by the presence of the LED and thus the energy produced by the collapsing magnetic flux is converted to light by the LED.
The circuit operates at approx 200kHz, depending on the value of the base resistor and physical dimensions of the transformer.
The circuit draws 85mA from the 1.5v cell and the brightness of the LED was equivalent to it being powered from a DC supply delivering 10 - 15mA.

Say what??  No mention of "resonance" or "RLC" again!

[MileHigh]

http://www.talkingelectronics.com/projects/CircuitTricks/CircuitTricks-2.html

CIRCUIT 3:

The third circuit uses feedback from a transformer to turn the circuit ON to a point where it is fully turned on. It is taken from our LED Torch Circuits article. The cycle starts with the 2k7 resistor feeding current into the base of the transistor. This starts to turn the transistor on and current flows in the 60 turn winding and produces magnetic flux that cuts the turns of the 40 turn winding. The 40 turn winding produces extra voltage that adds to the original voltage and this allows extra current to flow into the base of the transistor to turn it on more.
This continues until the transistor is fully turned on. This action is called positive feedback or more accurately REGENERATION.

The three circuits operate in exactly the same mode. This mode is called a SWITCHING MODE.  They change from one state to another VERY QUICKLY.
This action is called a SWITCHING ACTION or DIGITAL ACTION or DIGITAL MODE. There are basically two types of circuits, DIGITAL CIRCUITS and ANALOGUE CIRCUITS (also called audio circuits). An audio circuit operates over a smooth range of low output to high output. A digital circuit goes from one state to the other very quickly.
When this change is produced by the components within the circuit, the action is called REGENERATION because the action cannot be stopped and takes the transitor(s) from the state of not being turned on to the state of being fully turned on.

What the hell?

[hoptoad]

snip...
Quote from Clive in above video info: "There are a few variants on the design which add extra components to improve efficiency, but a true Joule Thief uses a single transistor, 1K resistor, hand wound ferrite bead transformer and the LED you want to light."
Bill

So if I substitute the 1K resistor for a 980 ohm, or I substitute hand wound for machine wound, or ferrite for air, etc, then it's not a JT.
Can you see how arbitrary and silly that notion is.?

Since JT is a vernacular term, and not an accepted Electrical Engineering term, then quite frankly, we can call anything a JT if we like and still be correct.

General language dictionaries (like Wikipeadia) reflect common usage and are therefore descriptive not proscriptive.

It seems that MH is not the only person who wants to place arbitrary parameters on what constitutes a JT.
So he (Clive) may have been the first to coin the term JT, but he doesn't own the term any more than the person who first used the term electronic to describe a particular device. As if arbitrarily deciding that only that very specific device can in any way be called 'electronic'.

A f.....g storm in a teacup really.
@Tinman, thanks for your sharing of your time on the bench.

cheers