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Require inductor help

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KevinW

Member
Hi, new guy here just joined and I'm trying to put together this circuit http://streampowers.blogspot.ca/2013/08/build-solar-garden-light-circuit-diagram.html
It's a solar garden light with a couple of inductors but the author hasn't given much information on the T40 and T60 coils.
I've been trying to search for them on line without success.
I can make them but the information is vague, "The coils in this circuit require a core material F29 and they must be made with wire of 0.095 mm in core 2.6x6mm."
It appears to be 19 gauge wire, the core is missing one dimension and it leaves out the number of turns for each coil.
The frequency for the coils is also missing but I'm guessing it's in nH.
Not sure if the value can be determined from the schematic so I'm asking for help from the members here.
Thanks.
Kevin.
 
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JLNY

Active Member
Welcome to ETO!
I'm guessing that the marking of 40t and 60t on the schematic are meant to imply that they are 40 turns and 60 turns, respectively. I believe that the inductors for a Joule thief boost configuration would actually be wound together on one core as a flyback transformer rather than two separate inductors. There are plenty of articles online showing how to wire up joule thief tranformers, and keep in mind that the direction of the windings needs to be connected correctly for the joule thief to work correctly.

Also, the article says 0.095mm as opposed to 0.95mm, so the wire gauge would be closer to 38 or 39 AWG instead of 19 gauge wire. I think you may have misplaced a zero hehe :D

It should also be noted for the sake of safety that the battery shown in the schematic is probably meant to be a 1.5V rechargeable NiMH battery and not an alkaline battery or any other kind of battery.
 
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KevinW

Member
Thank you for the welcome and wire correction, what would I expect the complete core size to be?
The author states in core 2.6x6mm, that appears to be 2.6OD, 6mmID but he leaves out the thickness of the core.
It would be simple enough to buy the cores and wind them myself knowing 40 and 60 are the number of turns and the wire gauge being 38 .
When stating the number of turns, would this be the individual wires of 40 turns each or the combination of the two wires making 40 turns?
I think it is the combination of both wires around the coil making 40 turns.
I've been searching for the past few days and not having much luck finding the information due to the lack of frequency.Thanks for the assistance.
 

JLNY

Active Member
Hmm. You make a good point about the core dimensions. I'm not sure if those dimensions are the ID and OD, or maybe the OD and height? Joule Thief circuits are fairly robust, so they are not super picky about having an exact core size or a particular number of turns to work. I might just look up other joule thief designs on the internet with better documentation and maybe experiment with whatever they used.

As for frequency, I believe F29 is a type of nickel-zinc ferrite material optimized for use at several MHz, but from what I can tell most joule thief circuits run in the tens of KHz range or so, so I don't know that it is necessarily the best material to use, anyway. These circuits are not very precise about what frequency they run at, and it depends a bit on the type of core used and the numbers of turns. A while back, I wound several dozen turns of 37 gauge wire around some random ferrite I found in a CFL light bulb ballast and had it oscillate just fine in a Joule thief circuit. It ran at such a low frequency that one could audibly hear the coil whining.

I think the article specifies the turns individually for two separate wires wound on the core-- one wire with 40 turns and one with 60.
 

audioguru

Well-Known Member
Most Helpful Member
Why make it when you can buy a solar garden light for $1.00 and it has a solar panel, LED, IC instead of transistor, diodes, inductor, capacitor and case. Then its Ni-MH rechargeable battery is free. Many of them use a colors-changing LED.
 

KevinW

Member
These circuits are not very precise about what frequency they run at
That's the impression I got when I see people using the cfl coils as is.

The reason for making it is I want to mount the solar panel on the outside of a patio umbrella and put white lights under the umbrella.
I like the idea of incorporating a joule thief to get all the energy from the battery.
If I purchased a light I would end up tearing it apart and rebuilding it.
There is another joule thief that doesn't use the inductor coils.
http://www.ebay.com/itm/Joule-Thief...007934?hash=item2597a5af7e:g:RH8AAMXQiFxR~gop
The oscillation frequency is 70KHz, not sure if this would work.
 

JLNY

Active Member
That joule thief would work as well. It still uses an inductor-- just a surface mount one as opposed to a slightly larger toroidal one (the inductor is the roundish component on the left marked with "171"). Basically any boost converter is going to require a transformer or inductor of some kind.
 

KevinW

Member
I believe that the inductors for a Joule thief boost configuration would actually be wound together on one core as a flyback transformer rather than two separate inductors
Does this schematic show two separate cores with only one winding on each core?
Or is it really just one core with two separate windings that are different in length?
upload_2017-3-4_17-11-12.png
 

JimB

Super Moderator
Most Helpful Member
It is two separate windings on one core, so that there is magnetic coupling between the two windings.

JimB
 

audioguru

Well-Known Member
Most Helpful Member
A joule thief dimly lights only one LED. The LED can be seen at night but it does not light up anything. Your idea about LEDs under an umbrella needs much more power.
 

KevinW

Member
Thanks Jim.

LEDs under an umbrella needs much more power.
That's a good point, he's got two white led's running on one 1.5 volt battery.
What if I step it up to two batteries for 3 volts?
Just enough light to see someone across the table.
I don't require much light and two 3 volts led's I think would do it.
 

audioguru

Well-Known Member
Most Helpful Member
The white LEDs use at least 3V. The joule thief already steps up the voltage from the 1V to 1.3V battery but its current is too low. Increasing the input voltage might just destroy the circuit.
Did you notice that in the joule thief video the light beam of the LED is extremely narrow so that it looks brighter?

Try a cheap solar garden light under the umbrella to see if it is bright enough.
 

KevinW

Member
I'll have to rethink this and dump the joule thief and look for another source of light.
Thanks everyone for taking the time to look at this and comment.
 
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