Joule Thief 101

[tinman]

Brad:

With that kind of logic I can throw spaghetti against the wall and claim it is a Joule Thief also.  Sorry, but you are not going to make up the rules as you go along to suit your fancy and make everything you say "right."  Everybody knows what a Joule Thief circuit is.  If you have another circuit that you claim does what a Joule Thief does, then show it.

No schematic, no explanation, no timing, no nothing.  Just a bunch of squiggly lines on a scope display that you claim is a "Joule Thief" to suit your fancy.



All that I see is a squiggly line.  It could be a dial tone from a phone for all I know.

If you can't present substantive data to make your point, then it's all just a mushy word salad that means nothing.  Take a look at some of Itsu's clips and postings for his presentation style and reporting of his results and contrast that with what you are doing.

MileHigh

"The coil is placed between the two large magnets within that housing,and eliminates any inductive coupling between the two windings."   That's just more word salad.  You seemingly just made up a "rule" that a coil placed between two magnets will eliminate any inductive coupling between the two windings of the coil.  It's not true and you are right back at square one showing that you haven't grasped one of the most basic concepts in electronics.  Just make it all up as you go along to suit your fancy and please yourself.  Who cares about those pesky details.

No MH. Here is the difference between bench time and book time--i work on the bench,and you work from the books.

Below is 3 circuit's,and all are LRC circuits. If there was no C involved,then the circuits would not work. The two coils are separate coils MH,and you can place either of the coils where ever you want-even having each coil in there own faraday cage,the circuit will still oscillate,although there is no inductive coupling between L1 and L2. The circuits work due to the miller capacitance effect.

So now we know that the JT circuit is indeed a RLC circuit. You obviously do not do your home work MH,as many people have replicated these circuit's,and also shown that there is no inductive coupling required between L1 and L2 for the circuit to work as a joule thief.

I ask you again MH-->do you know what a JT is ?.

Quote wikipedia
A joule thief is a minimalist Armstrong[1] self-oscillating voltage booster that is small, low-cost, and easy to build, typically used for driving light loads.

It can use nearly all of the energy in a single-cell electric battery, even far below the voltage where other circuits consider the battery fully discharged (or "dead"); hence the name, which suggests the notion that the circuit is stealing energy or "joules" from the source. The term is a pun on the expression "jewel thief": one who steals jewelry or gemstones.

The circuit is a variant of the blocking oscillator that forms an unregulated voltage boost converter. The output voltage is increased at the expense of higher current draw on the input, but the integrated (average) current of the output is lowered and brightness of a luminescence decreased.

So you see MH,the joule thief is not one single circuit,it is a name used to describe an effect,and as i said,there are many different types of circuits that can achieve this effect.

So i am not making my own rules MH,i am stating fact's-unlike your self,that insists that a JT is 1 particular circuit-->which it is not.


Brad

[Magluvin]

After looking around at how most JTs are made, I wound a core with 8 strand twisted for the driven winding and 4 strand for the trigger winding. Lasersaber uses Litz in his latest gidgets.  Both are 29 turns each. The 8 strand winding will be used as is for the first tryouts, then will be spilt into 2 pairs of 4 strands and connected bifi to increase capacitance to see what resonant freq can be had there.

Should have it up n running in a bit.

Mags

[tinman]

After looking around at how most JTs are made, I wound a core with 8 strand twisted for the driven winding and 4 strand for the trigger winding. Lasersaber uses Litz in his latest gidgets.  Both are 29 turns each. The 8 strand winding will be used as is for the first tryouts, then will be spilt into 2 pairs of 4 strands and connected bifi to increase capacitance to see what resonant freq can be had there.

Should have it up n running in a bit.

Mags

I will throw a cool joule circuit together as well. It will be interesting to see the difference in wave forms.

[hoptoad]

What is a JT to you MH? .Do you know why it is called a JT ?.
It was called a joule thief because it can drain a lot of the remaining energy(joules) from a battery that would otherwise be considered dead. There are many variations to the circuit that can achieve this,and not 1 circuit alone can be considered to be !the! joule thief circuit. You have posted the most common and simple circuit that you claim to be !the! JT circuit. You have posted the effect based around a circuit,in stead of a circuit based around an effect. This is like presenting a vehicle that suits tires,in stead of tires that suit the vehicle.
....snip
Brad

Having built many a JT over the years, I can say that with the right , high gain, low powered transistor, you don't even need a base connection to the transistor, or even two coils, nor even a single resistor. You can get away with a single collector coil, transistor, led, battery and a few wires to connect them all up.

Some transistors will self oscillate when the base is open circuit right at power switch on. Others just need a quick touch of the finger to the base to get them going after power switch on. Simple bi-polar, high hFe transistors work well in this open base mode of operation.

Most mosfets don't work so well in this configuration, often due to latching when the gate is left 'floating' without a pull down resistor.
So I definitely agree Tinman, JT's come in all manner of configurations, some more efficient than others, but all doing the same thing.

There is no singular form of JT, but there are many different oscillator configurations that produce the same desired outcome of running a led on voltage sources that are below the led voltage threshold. Or using vernacular I know your familiar with, " they'll run on the sniff of an oily rag".

I've found simple blocking oscillators using off the shelf components to be the easiest to build, and they exhibit a reasonable stability and robustness over a range of voltage sources.

Cheers

[Magluvin]

Ok. She is working. No issues.  Started with a 1k resistor then put in a 1k 10turn variable with a 100ohm res as a minimum.

The first scope shot is of the led across the transistor and the second is the led across the coil winding.  The pk-pk is greater with the led across the coil and the freq increased also, similar to the circuit sim had shown.

Mags