The post provides interesting information regarding the making of a 1.5V to 12V converter circuit using a couple of transistors and an inexpensive coil. The idea was requested by Mr. Keith.

The Circuit Request

I found your blog and have searched for an answer to my question but I'm just not finding it....

What I want to do is use 4 x 3v "2032" coin batteries connected in parallel to get long lasting life out of them. Then using a "Joule Thief" circuit up the out-put voltage to 12.5v - 14v to drive a set (3) of color changing LED's or a 12v LED light bulb found on ebay (here is the link to the bulb...

Now here is the other part of my problem, I don't want to use a wire wound transformer !!!! I would like the Joule Thief circuit to use transistors or some other easy to get materials because at the end of all of this I am going to encased the whole project in clear resin..

Any help would be great... A wiring schematic with parts labeled would help also.



Solving the Circuit Request

Thanks for contacting me!
I am afraid without a coil it wouldn't be feasible to create a joule thief effect, because the coil is the maincomponent which enables complete extraction of energy from a depleting source.


Feedaback from Keith

I thought that is what you would say. Is there a way to design it with a ferrite core coil that is available "off the shelf" i.e. Radio Shack or Digi-Key, so I don't have to make my own.

And could you design it? Also would there be any issues with encasing this project in liquid resin? The resin will cure within 24 hours and I am just wondering is there any issue with the coil not being able to get "fresh air" and getting too hot and eventually burning up. By the way the on/off switch is a mercury switch.

Would any of these work? I know that my power requirements maybe more or less than 330uh, I just search for that size because I remember seeing that being used by this project:


If none of this works can you please send me a wiring schematic with labels for parts that does include a wire coil and I will just build it that way.

Thanks again,



Analyzing the Circuit Idea

The 1.5V to 12V converter circuit provided in the above "instructables" link would possibly do the job. The second digikey link coil is the one which exactly suits the design, so you can try it out.

Epoxy resin sealing would be fine, it won't do any harm to the inductor.


Circuit Diagram

Joule thief no ic or toroid 07b.jpg

Joule thief no ic or toroid 08b.jpg


Inductor 300uH or similar (Picture)


CHOKE RF CONFORMAL COATED 330UH | 8230-80-RC | M8199-ND | Digi-Key Corp.

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