Joule Thief - solar garden light

Thread Starter

aaad2

Joined May 30, 2012
50
I would like to make this circuit:


the circuit diagram is from this website:
http://www.evilmadscientist.com/2008/simple-solar-circuits/

I can get all the parts apart from the toroid bead/core.
I know you can probably buy it from the Internet but it is not cheap and I want to keep the price to a minimum.

For people who do not know what a joule thief is:
http://www.instructables.com/id/Make-a-Joule-Thief/

So I would like to know if this would work for other things such as a nail?
Does it have to be a magnetic core/bead? or does the core has to be made from Iron?

Thanks in advanced and sorry for blabbering on.
 

bug13

Joined Feb 13, 2012
1,708
You can make one yourself easily following the instructable, or get one from old pc power supply, motherboard, energy saving light bulb or any old electronics, size is not critically important.

Ps: do follow the safety step requirement when opening old electronics etc.
 

acmefixer

Joined Aug 4, 2011
17
I would like to make this circuit:


the circuit diagram is from this website:
http://www.evilmadscientist.com/2008/simple-solar-circuits/

I can get all the parts apart from the toroid bead/core.
I know you can probably buy it from the Internet but it is not cheap and I want to keep the price to a minimum.

For people who do not know what a joule thief is:
http://www.instructables.com/id/Make-a-Joule-Thief/

So I would like to know if this would work for other things such as a nail?
Does it have to be a magnetic core/bead? or does the core has to be made from Iron?

Thanks in advanced and sorry for blabbering on.
No, the coil core can be made of air. The coil can be made from two 16 foot or 5 meter lengths of 24 AWG or 0.5mm wire wound bifilar (at the same time) onto an AA cell, which is then removed and the coil tied with wire ties, tape or even dental floss. This works okay, and is cheaper than using a toroid. But it's much larger and bulkier. You can see one here that I made from cat5 wire.

The circuit you chose uses a 2N3906 to turn on and off the current from the AA cells, this can be more than 200 mA which is more than the maximum allowed for a 2N3906. Even a BC327 will have a difficult time. To fix this. move the top lead of the right side winding connected to the collector to the emitter (plus). This reduces the current through the 2N3906 to only the base current of the 2N3904, which turns the 2N3904 off. But the first thing you should to do is replace the anemic 2N3904 with a decent transistor such as the 2N4401, PN2222A or BC337.
 

BMorse

Joined Sep 26, 2009
2,675

Thread Starter

aaad2

Joined May 30, 2012
50
No, the coil core can be made of air. The coil can be made from two 16 foot or 5 meter lengths of 24 AWG or 0.5mm wire wound bifilar (at the same time) onto an AA cell, which is then removed and the coil tied with wire ties, tape or even dental floss. This works okay, and is cheaper than using a toroid. But it's much larger and bulkier. You can see one here that I made from cat5 wire.

The circuit you chose uses a 2N3906 to turn on and off the current from the AA cells, this can be more than 200 mA which is more than the maximum allowed for a 2N3906. Even a BC327 will have a difficult time. To fix this. move the top lead of the right side winding connected to the collector to the emitter (plus). This reduces the current through the 2N3906 to only the base current of the 2N3904, which turns the 2N3904 off. But the first thing you should to do is replace the anemic 2N3904 with a decent transistor such as the 2N4401, PN2222A or BC337.
Hi, For the circuit that I will be making(when I get the parts together :) ), I will not be using a 4.5v solar panel, I was thinking of using about 2.4v solar panel and 1 1300mAh battery. This allows it to charge all day without problems.

Another thing is that I will be making many of these, not just one.

I used to have some garden lights but I broke them(lawn mower - dont ask...)

when I opened up their circuit, it was very simple, a blob of black stuff(controls the circuit), resistors, 1 tiny solar panel, 1x AAA battery and 1 LED.

So which transistors do you recommend me changing to now? Or should I just stay with the ones from the circuit diagram?

Thanks
 

Thread Starter

aaad2

Joined May 30, 2012
50
No, the coil core can be made of air. The coil can be made from two 16 foot or 5 meter lengths of 24 AWG or 0.5mm wire wound bifilar (at the same time) onto an AA cell, which is then removed and the coil tied with wire ties, tape or even dental floss. This works okay, and is cheaper than using a toroid. But it's much larger and bulkier. You can see one here that I made from cat5 wire.
Furthermore, I have noticed that some of these joule thief is made from bare wire while others have a pastic coating (normal wire without plastic coating being stripped off).

Is there any difference(e.g. current etc...) in these techniques used?
 

takao21203

Joined Apr 28, 2012
3,682
Get a defunct CFL somewhere. Twist off the metal shielding from the socket using pliers. Pretty easy. They contain a small toroid core, which should be great for a joultheif.

If you can't buy them inside the UK, most electronic appliances have some kind of EMI filters inside them. Even some USB cables have one! For sure most people have old USB leads that don't fit to anything anymore.

There are many electronics people in the UK, for sure someone has extra cores and can send them to you. Maplin does not have toroid cores as such.
 

Audioguru

Joined Dec 20, 2007
11,251
Bare wire is not used to make a transformer or an inductor. It will short the circuit. Instead the wire has an enamel coating as its insulation.
 

ErnieM

Joined Apr 24, 2011
7,996
I used to have some garden lights but I broke them(lawn mower - dont ask...)

when I opened up their circuit, it was very simple, a blob of black stuff(controls the circuit), resistors, 1 tiny solar panel, 1x AAA battery and 1 LED.
I've delved deeply into garden lights, that's not what is inside them.

You are correct there is a 1 tiny solar panel, a battery, and a LED.

That's not a resistor, it's an inductor.

That blob of black stuff that controls the circuit is an IC. Should you find one with the discrete device it has 4 leads. However, I have never found a vendor for that device and I do not have any handy to read off the number.
 

Wendy

Joined Mar 24, 2008
21,848
Any simple low power oscillator will work, but it needs to be a square wave to generate the inductive kick (that converts voltage to current).
 

Thread Starter

aaad2

Joined May 30, 2012
50
I've delved deeply into garden lights, that's not what is inside them.

You are correct there is a 1 tiny solar panel, a battery, and a LED.

That's not a resistor, it's an inductor.

That blob of black stuff that controls the circuit is an IC. Should you find one with the discrete device it has 4 leads. However, I have never found a vendor for that device and I do not have any handy to read off the number.
So for the circuit that I will be building, do you recommend me changing anything?

One of the one person recommended me to change the transistors but I then mentioned that I will be using a lower voltage solar panel(about 2-2.4v solar panel) with only 1x 1300mAH.[Something that is similar to the normal garden lights].

I will be using a nail(possibly a very thick one) and wrapping around it with loads wires(with the plastic coating) <-- this will then be used for my 'joule thief' part!

I will buy the transistors from ebay but not sure if I should buy the transistors from my circuit diagram (this links back to my question - should I change the transistors or use the ones the other person on this thread has recommended?)

Thanks in advanced.

Btw, you guys know sooooooo much about circuits :p
 

Audioguru

Joined Dec 20, 2007
11,251
A nail is a very poor inductor. The circuit probably will not work or if it does work then the LED will be very dim.

A solar garden light uses a 400mAh or 600mAh Ni-Cad battery cell and a real ferrite core inductor. It lights the LED at night for about 8 hours following a sunny day in summer. The solar panel is too small to fully charge a rechargeable cell with a capacity more than 600mAh so half of your 1300mAh cell will be wasted.
But the nail will waste most of the charge from the battery cell anyway.
 

Thread Starter

aaad2

Joined May 30, 2012
50
A nail is a very poor inductor. The circuit probably will not work or if it does work then the LED will be very dim.

A solar garden light uses a 400mAh or 600mAh Ni-Cad battery cell and a real ferrite core inductor. It lights the LED at night for about 8 hours following a sunny day in summer. The solar panel is too small to fully charge a rechargeable cell with a capacity more than 600mAh so half of your 1300mAh cell will be wasted.
But the nail will waste most of the charge from the battery cell anyway.
just to be clear, anything can be used to make the toroid part of the joule thief, but would have an effect on the intensity of the LED.

a toroid made of air: low LED intensity
magnets, ferrite, iron: High LED intensity

Am i correct? :)
 

Audioguru

Joined Dec 20, 2007
11,251
just to be clear, anything can be used to make the toroid part of the joule thief, but would have an effect on the intensity of the LED.

a toroid made of air: low LED intensity
magnets, ferrite, iron: High LED intensity

Am i correct? :)
No.
A ferrite core torroid is supposed to be used because it is designed to be a good efficient inductor for the fairly high frequency. A nail is a joke, and a poor inductor.
 
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