Joule Thief

[gyulasun]

Gyula:

I think you may have misunderstood my post.  I was talking about the guy in the blog link that you posted wanting low perm. not Conrad.  Sorry if I was not clear.

But yes, I agree that the good folks here will share all of what they have learned to help Conrad, and anyone, work with these fascinating circuits.

Conrad:

When you get your lights shinning in Austria, post some photos.  I'll bet that will be a beautiful site.

Bill

Bill, yes I misundertood you, sorry. 

However I tried to find in Watson's blog link I gave where he wrote he had wanted low perm cores but I could not.

I read where he dealt with cores:

"This SJT used a toroid core from All Electronics, part number TOR-54. I put a single turn (piece of straight wire) through the hole in this core and it measured 0.08 uH (I measured several of them to get an average). This means it is a low permeability core, much lower than the usual ferrite RFI suppressor sleeves that I've used (compare that to the charcoal TOR-23 cores they sell, which have 0.48 uH per turn). It also means that I have to use more turns to get the inductance up to 100 uH."

If you may have thought about this part of the blog here I think he only concludes the TOR-23 has a low perm and this involves using more turns to get inductance up.

So I am puzzled where you mean his wanting the use of low perm cores, sorry for this.

rgds,  Gyula

[Pirate88179]

Bill, yes I misundertood you, sorry. 

However I tried to find in Watson's blog link I gave where he wrote he had wanted low perm cores but I could not.

I read where he dealt with cores:

"This SJT used a toroid core from All Electronics, part number TOR-54. I put a single turn (piece of straight wire) through the hole in this core and it measured 0.08 uH (I measured several of them to get an average). This means it is a low permeability core, much lower than the usual ferrite RFI suppressor sleeves that I've used (compare that to the charcoal TOR-23 cores they sell, which have 0.48 uH per turn). It also means that I have to use more turns to get the inductance up to 100 uH."

If you may have thought about this part of the blog here I think he only concludes the TOR-23 has a low perm and this involves using more turns to get inductance up.

So I am puzzled where you mean his wanting the use of low perm cores, sorry for this.

rgds,  Gyula

It was this statement that led me to believe this:

"This means it is a low permeability core, much lower than the usual  ferrite RFI suppressor sleeves that I've used (compare that to the  charcoal TOR-23 cores they sell, which have 0.48 uH per turn). It also  means that I have to use more turns to get the inductance up to 100 uH."

I might have misunderstood this comment but, it appeared to me he wanted a lower perm.  Hey, I could be wrong, God knows it has happened before.

Bill            ***EDIT***  In re-reading this for like the 4th time I see that I was not correct so, ignore my posts about this and my question.  Sorry.

[detrix42]

@all:
Hello everyone.  I have been trying to wrap my head around these joule thief circuits.  I have built several.  Recently I took a toroid from a motherboard and using 26awg wire, made primary and a secondary coils.  Took me a while to get it right, but I got it.  I can get about 45v out of it.  Now what I am trying to wrap my head around is... How do I do anything (besides lighting diodes) useful with it.  Anytime I try to add an electronic component to it, I kill the oscillations, or something like that.  For example, I came across a piezo electric buzzer, needs 6v.  I thought no problem for a joule thief, and in fact I did get some sound, but not very good.  I also want to hook a joule thief to a larger transformer, but I am not sure how.  Thanks in advance for all the help.

[crowclaw]

@all:
Hello everyone.  I have been trying to wrap my head around these joule thief circuits.  I have built several.  Recently I took a toroid from a motherboard and using 26awg wire, made primary and a secondary coils.  Took me a while to get it right, but I got it.  I can get about 45v out of it.  Now what I am trying to wrap my head around is... How do I do anything (besides lighting diodes) useful with it.  Anytime I try to add an electronic component to it, I kill the oscillations, or something like that.  For example, I came across a piezo electric buzzer, needs 6v.  I thought no problem for a joule thief, and in fact I did get some sound, but not very good.  I also want to hook a joule thief to a larger transformer, but I am not sure how.  Thanks in advance for all the help.

Hi detrix,

Well what do you want to do with it? The basic JT circuit cannot produce high levels of DC current necessary for certain projects when powered from a single AA cell. What has been demonstrated is the high voltage short duration spikes produced from this type of circuit can power strings of LED's... see the work of Bill and Jeanna of what they have achieved. In saying that various other designs around the same circuit design principles have evolved to charge up Nicad and Lead Acid batteries. Even small DC motors have successfully been run. Rather than me  explain in depth what can and can't be done take a look back over this thread to get some ideas and thoughts from the many who have posted excellent circuits and projects. If your not to sure about the technicalities don't be frightened to ask, but it's well worth gaining a good theoretical insight about the basic principles of how the circuit works. Once a sound knowledge and understanding has been gained, then they're be no stopping you. One last point I'll mention is... if you attempt to load the circuit with a device that needs more current draw than the secondary circuit can deliver the oscillations will diminish or even stop. LED's in particular are what's known as high impedance devices (their internal resistance to the flow of an electrical current is quite high for a give light output) so they present only a relatively small load on the circuit. BTW make sure you include a variable pott in the base circuit, this will enable you to "tune" the characteristics of the inductor circuit to achieve the best output pulses. Hope this helps. Regards.

[detrix42]

@crowclaw:
I have several working joule thief circuits, and have learned a lot.  My desire is to run a Newman motor that I am building.  I will need help in designing a JTC to deliver around 1000v.  If you have not seen my videos yet here is a link to one:
http://www.youtube.com/watch?v=F6qLiAeyPng

I am willing to use, say a 12v source.  I just need to know what is a proper transistor to deliver 1000v.  I have used a disposable camera's flash transformer to get up to 350v from a AA battery.  Technically, I am not concerned about how much current there is.  In a Newman motor, it is desired to keep the current as low as possible and the voltage high.  Though the coil in the video link above is only about 50ohms, and that would try to pull way to much current from my current JTC setup.  I have come across some bigger transformers, and want to use them.  So the question is, what components (transistor mainly) do I need to go from 12v to what ever I can get out of one of these transformers I have? 

Thanks for your input Crowclaw, it has me thinking.