Small Joule Thief

I saw a tiny joule thief here:  I wanted to replicate the size, but leave the application open for use in different projects.  By following this excellent instructable: I was able to fit my circuit inside a 5x5 square of perfboard. It happily powers 3 leds in parallel. 



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9 Discussions

That looks awesome!! Makes me want to go even smaller...Where is the resistor though? Underneath the board disqualifies you from competition(!)


5 years ago on Introduction

guys i want to makeone of this but i only have C1815,A1510Y transistor.. and dont know the resistor to use because i dont know the color to choose..


This is very neat, very clean looking as well!
I was wondering if you remembered where you got your ferrite bead from. I can't seem to find any. Also, I noticed you have only 5 wraps where most other thiefs use upwards of 20, does that effect the performance at all?

3 replies

Hi! Thank you! I found the tiny ferrite bead inside a Philips "Genie" 11w CFL bulb. The instructable I followed recommended 6-11 turns on the bead, with 11 being the maximum advised. I used the smallest wire available to me and just squeezed 5 turns. It has been running 3 UV leds in parallel for a few nights now from an otherwise dead battery. Everything seems to work OK, but I'm not really sure how to test performance to be honest!

Okay, thank you! The only ferrite I have been able to find is much too big, I will continue to scavenge :)


Reply 6 years ago on Introduction

Thank you so much for your very informative and helpful comment! I will be sure to take your advice.