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Solid States Devices => Joule Thief => Topic started by: ikram85 on June 02, 2015, 05:43:37 PM

Title: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: ikram85 on June 02, 2015, 05:43:37 PM
Hi everyone!

Normally I come here to learn and make cool projects, but today I need to ask some help. We need to make a led glow, I suggested using a Joule thief but we only have a few components to make it and not much knowledge to make it.
it's giving us 1.2v aprox and 15/30ma aprox, one made with a small toroid works quite well but we need to make one without it.

we have 2N2222a
2N3904
and BC557 transistors
some caps
resistors
two types of inductor 47mH and 470mH
small 3.3v smd Leds

We need to make it small and simple and brigther as possible, any ideas to assemble it? tell me if we need to change some components
thank you for reading me
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: mscoffman on June 03, 2015, 10:27:55 PM
   
Here is a reference to the start of a string of posts about toroid-free JT's on here.
You will have to find a reference pathway for yourself;


---

hi everyone,

I have just uploaded a youtube video of my recent discovery-  Powerful toroidless joule thief
http://www.youtube.com/watch?v=QP8PkgT1T9o (http://www.youtube.com/watch?v=QP8PkgT1T9o)

This is the 4th version of my toroidless joule thief circuit as there are other types shown in my youtube channel :sanjev21 which is not using toroid and yet able to light led brightly.This is the final version.

Without the use of  any toroids would take the overall cost building a joule thief circuit to a new low.Here i am talking about avoid buying toroids which cost money unless you got some spares from salvage after which you still need to wind the coils.

The  Powerful toroidless joule thief  circuit can be assembled in less than 5minutes on a breadboard once you got the components ready.

The schematic is revealed in the video.

Component list
2222 transistor
4.7 kohms resistor
10nf capacitor
100uH x 2 inductor
Led
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: ikram85 on June 03, 2015, 10:37:07 PM
Thank you very much mscoffman! :D i'll check that out
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Pirate88179 on June 04, 2015, 07:13:14 AM
Here is another one:

https://www.youtube.com/watch?v=KFswGMJ7QiI (https://www.youtube.com/watch?v=KFswGMJ7QiI)


You can make one with an air coil but it needs a lot more turns...like around 1,000 depending upon the other components.

Here is one with an air core:

https://www.youtube.com/watch?v=wNxfsS_2PVU (https://www.youtube.com/watch?v=wNxfsS_2PVU)

Bill
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Groundloop on June 04, 2015, 04:02:20 PM
Hi,

The attached oscillator can be built with SMD components. The two coils does
not need any coupling between them at all. The coils can be separated in distance.
The resistor is there to give the transistor a small voltage bias so that the oscillator starts
and can be from 100K and up to 1M, 1 mega Ohm is typical used here.

Much of the oscillator frequency is determined by the value of the coil and capacitor at
the base of the transistor. 1 to 100 nano Farad will work OK for a LED driver. You can use
almost any type of LED on the output. Good luck with your project.

GL.
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: forest on June 04, 2015, 05:06:09 PM
Can you also post schematic of JT with mosfet transistor ?
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Groundloop on June 04, 2015, 07:58:25 PM
Can you also post schematic of JT with mosfet transistor ?

Forest,

Let's say you want to light a LED spot light (12 Volt 3,5 Watt) from a 1,5 Volt input (battery  or power supply)
using normal n-type mosfets. Your problem will be that mosfets needs a fairly high gate voltage to switch,
typical +15 to switch properly on and -15 volt to properly switch off again. So you will need to make that high
voltage swing locally in your circuit to do so when your input voltage is so low. You can use a IC that converts
your low voltage to 15 volt and then run a mosfet one transistor circuit from that voltage. Or if you do not want
to use a IC but only discrete components, then you can convert only the gate voltage to a higher voltage and
run the mosfets switching process from your low voltage input. And there is probably other ways to do it
by using special mosfets that are default on or have low gate voltage threshold etc.

Attached is a circuit that will switch a normal n-type mosfet on and off. The circuit uses two normal npn transistors
to make a simple oscillator. This oscillator runs two small toroid transformers so that we get a +15/-15 volt
gate voltage for the mosfets. Then the mosfets switches another toroid so that we can transform the low
input voltage up to +12 volt to drive our LED spotlight. The winding ratio of the PTRF1 transformer can be
anything you want, so it is theoretical possible to drive a 230 VAC LED bulb from a low voltage input.

GL.
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Groundloop on June 04, 2015, 08:24:06 PM
Can you also post schematic of JT with mosfet transistor ?

Forest,

This circuit will probably also work. A low volt gate threshold mosfet is used in this circuit.
(I have not build and tested this circuit, but I see no reason that it will not run.)

GL.
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Groundloop on June 05, 2015, 10:45:00 PM
Here is my Eagle CAD implementation of a mini JT.
The pcb is approx. 10mm x 20mm and still solder-able
by hand.

GL.
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: ikram85 on June 07, 2015, 02:57:46 AM
Hi,

The attached oscillator can be built with SMD components. The two coils does
not need any coupling between them at all. The coils can be separated in distance.
The resistor is there to give the transistor a small voltage bias so that the oscillator starts
and can be from 100K and up to 1M, 1 mega Ohm is typical used here.

Much of the oscillator frequency is determined by the value of the coil and capacitor at
the base of the transistor. 1 to 100 nano Farad will work OK for a LED driver. You can use
almost any type of LED on the output. Good luck with your project.

GL.

Thank you very much to all of you, the first one works pretty well, we are learning pretty well how these amazing circuits work, I'm going to try this one, maybe it glows more, I'll use 1M ohm then, thank you all again
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: ikram85 on June 07, 2015, 02:59:12 AM
Thank you very much to all of you, the first one works pretty well, we are learning pretty well how these amazing circuits work, I'm going to try this one, maybe it glows more, I'll use 1M ohm then, thank you all again
could it be even smaller? wow, it's fantastic, looks very efficient :D I'm going to try also this one without dying, thx
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Groundloop on June 07, 2015, 04:06:16 PM
could it be even smaller? wow, it's fantastic, looks very efficient :D I'm going to try also this one without dying, thx

ikram85,

This is a more powerful JT that runs from a 9 Volt battery. This circuit will give
good light output from the 9 Volt battery until the battery is drained down to
approx. 6 Volt.

GL.
Title: Re: Need advise for a Joule Thief with 20ma 1,2v power source
Post by: Groundloop on June 08, 2015, 03:44:35 PM
The attached circuit works a little better than my first version of this circuit.

GL.