Joule Thief

[conradelektro]

To Resonanceman,

thank you for your hints on air coils, very interesting, I have to try the twisted wire. There is so much experience with JTs out there in this forum, great!

The following idea is going around in my head:

In order to keep the energy consumption of a Joule Thief down one should go for very short duty cycles over the LEDs (or any lamps one wants to light up). See the attached drawing.

Very short pulses, even spikes might be good, but with high frequency in the Megahertz.

This might best be achieved with a secondary which has no connection with the circuit (besides induction and resonance). As I see from other folks posts, the secondary was the big progress with the JTs.

And for high frequency the air coil comes into play because of its low inductance. It is also nice to get rid of the Toroid because good ones are hard to come by.

May be I am on the wrong track with the "duty cycles" and would like to hear comments from the master JT builders?

Greetings, Conrad

[crowclaw]

ok, ok.  The Flyback transformer may be a bit overkill.  I am considering it because I don't have access to a 3.5" toroid.  I have a bunch of 1" toroids, and a couple of disposable camera flash transfromers.  hmmmm.  I still don't know how to use the output of the joule thief in my motor.  My third motor's coils have a resistance of 1155ohms. This draws to much from my JTC. I plan on adding a lot more wire when funds allow.   

So in the mean time, I would like to get the Flash transformer to lite a CFL.  I think I can do this.

Hi detrix,

The reason behind using scrap was to save buying materials just to experiment with of course, old scrap power supplies from computers can produce a wealth of goodies including toroid's, scrap AC motors will provide a useful source of copper wire for winding you coils. You can use the ferrite flyback transformers core to wind your own JT! theres so much electronic scrap sent to land fill that your projects could cost next to nothing. Have a good look around. How do you intend to transfer the JT's output to your motor coil, or are you considering  using the coil as an integrated part of the JT circuit?... do you have a schematic for your project for me to look at should you need further help. Last point if you do use any of the flyback transformer windings be very careful of exposed connections!! you don't need EHT voltages

[crowclaw]

To Resonanceman,

thank you for your hints on air coils, very interesting, I have to try the twisted wire. There is so much experience with JTs out there in this forum, great!

The following idea is going around in my head:

In order to keep the energy consumption of a Joule Thief down one should go for very short duty cycles over the LEDs (or any lamps one wants to light up). See the attached drawing.

Very short pulses, even spikes might be good, but with high frequency in the Megahertz.

This might best be achieved with a secondary which has no connection with the circuit (besides induction and resonance). As I see from other folks posts, the secondary was the big progress with the JTs.

And for high frequency the air coil comes into play because of its low inductance. It is also nice to get rid of the Toroid because good ones are hard to come by.

May be I am on the wrong track with the "duty cycles" and would like to hear comments from the master JT builders?

Greetings, Conrad

Hi Conrad,

To conserve battery power you must work on very short duration pulses, this is where the JT circuit scores. The longer the duty cycle the more current is drawn from your battery due to the longer conduction cycle of your output transistor. If you are still unclear on this let me know. If you progress into the MHz regions you may have trouble with your transistors upper frequency responce!! Most of the types used for JT circuits may struggle. Must point out  should you experiment with circuits using antenna's or similar open loop circuits which are not using straight inductive power transfer techniques, you could end up transmitting powerful radio frequency interference across several broadcast bands and frowned upon by the authorities that monitor such things. Not one to dampen ones experimental challenges of course... just a friendly word of warning.

[detrix42]

Hi detrix,

The reason behind using scrap was to save buying materials just to experiment with of course, old scrap power supplies from computers can produce a wealth of goodies including toroid's, scrap AC motors will provide a useful source of copper wire for winding you coils. You can use the ferrite flyback transformers core to wind your own JT! theres so much electronic scrap sent to land fill that your projects could cost next to nothing. Have a good look around. How do you intend to transfer the JT's output to your motor coil, or are you considering  using the coil as an integrated part of the JT circuit?... do you have a schematic for your project for me to look at should you need further help. Last point if you do use any of the flyback transformer windings be very careful of exposed connections!! you don't need EHT voltages

A friend of mine dropped off lots of electronic scrap.  Even a reel-to-reel tape player.  I have not gutted it yet.  There were also several decent sized transformers.  I like recycling electronic parts.

This was my original question.  I am not sure how to transfer the power of the joule thief to my motor.  Even if I do make a JTC similar to Jeanna's Light with 300 turns in the secondary, I don't think I can hook it directly to my motor.  My motor needs DC.  And at startup I need the voltage for about 2 seconds.  Once up and running, I only need the voltage for milliseconds.  I am believing the JTC may not be capable of drive my motor, at least not yet.  Once I have enough wire, where the resistance is high enough to not draw so much currrent from the joule thief, then a JTC might work.

Here is a simple schematic of my motor setup. This may not explain it very well. sorry.

[crowclaw]

I don't think I can hook it directly to my motor.  My motor needs DC.  And at start up I need the voltage for about 2 seconds.  Once up and running, I only need the voltage for milliseconds.  I am believing the JTC may not be capable of drive my motor, at least not yet.  Once I have enough wire, where the resistance is high enough to not draw so much current from the joule thief, then a JTC might work.

Here is a simple schematic of my motor setup. This may not explain it very well. sorry.

Hi detrix,
Hmmmnn!! what is the total DC resistance of your coil(s) that the HV supply will appear across. I presume the 2 second period is at start up before the motor gains momentum and the rev's increase? wow this is some project!