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About This Instructable

License:
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(https://cdn instructables com/FQ6/BADQ/IAJNRFZF/FQ6BADQIAJNRFZF MEDIUM jpg)
playmonkey
(/member/playmonkey/)
This is an introduction into the operation of a Joule Thief and a brief look at it’s PlayChimp Makes
(http://www.playchimp.com)
history. In November 1999 a simple circuit was published by Z. Kaparnik of a
transformer-feedback single-transistor voltage converter in Everyday Practical (/member/playmonkey/)
Follow 20

Electronics magazine. The Joule Thief circuit is based on the blocking oscillator
which predates World War II. Bio: Making energy saving and harvesting
devices with an ideal goal of going off-grid.
The circuit starts when the transistor is off. Current flows through the left hand
side of the transformer and through the 1k resistor, into the base of the More by playmonkey:
transistor. The transistor turns on slightly and produces a current in the collector
emitter circuit. This allows current to flow in the right hand winding of the
transformer and produce magnetic flux. This flux cuts the turns of the left hand
winding and produces a voltage that adds to the voltage produced by the
battery. (/id/Joule-
Thief-
This increases the current into the base of the transistor and the transistors Explained/)
turns on more. This continues and the transistor turns on more and more until it
cannot turn on any harder. At this point the magnetic flux in the right hand
winding is a maximum but is not expanding flux and thus the left hand winding
does not produce any additional voltage. The current into the base of the
transistor reduces and the transistor turns off slightly.
 The current through the right hand side of the winding reduces and the magnetic
energy in the core of the ferrite ring starts to collapse and produce a voltage (in
both windings) of opposite polarity. In the left winding, it starts to turn the
transistor off completely and in the right winding, it delivers this energy to the
LED. Now here’s the clever part. When the current is abruptly switched off, as is
the case with this circuit, a voltage is produced in both windings that has
opposite polarity to the original voltage and will be higher amplitude than the
original voltage.
This voltage can be 10 or even 100 times higher than the original voltage and
this is called the “Q” of the circuit. We are not creating something for nothing as
the voltage will be higher but the current will be lower than the current drawn
from the battery. The voltage produced by this circuit will be over 10v but a white
LED has a characteristic voltage of about 3.2v to 3.6v and all the energy in the
10v spike, and the accompanying current, will be delivered to the LED to
produce illumination. The LED starts to absorb energy at 3.2v and that’s why the
voltage across it never gets any higher than 3.6v.

Step 1: Quick Video

How a Joule Thief Works

Step 2: Components
 (https://cdn instructables com/FZE/JDYU/IAJNRFZK/FZEJDYUIAJNRFZK MEDIUM jpg)

1) NPN Transistor

2) 3V Super Bright LED (any colour will be fine)

3) Wiring (x2 meters)

4) Breadboard (http://www.ebay.co.uk/itm/170-point-Solderless-mini-
Breadboard-perfect-for-Arduino-proto-shields-/121599131538?
pt=LH_DefaultDomain_3&var=&hash=item1c4fdf7f92)*

5) Ferrite Core

6) 1K Ohm Resistor

The breadboard is not really necessary though for beginners it could be ideal to
help with further experiment too.

Step 3: Circuit Diagram

(https://cdn instructables com/F6O/3SAF/IAIFFOR6/F6O3SAFIAIFFOR6 MEDIUM jpg)

Step 4: Construction - Wiring the Toriod

(https://cdn instructables com/FDY/EJAO/

(https://cdn instructables com/FU (https://cdn instructables com/FA (https://cdn instructables com/F3

Wiring the toroid is the perhaps the most difficult part of constructing a Joule
Thief. Essentially you are creating two windings around the toroid (called a bifilar
winding). Take your time and don't rush especially if it's your first time winding a
toroid :) It's easier if the wires are different colours too.

1. Take two strands of insulting wire and thread them through the toroid as seen
in the first figure above: (Keep around 2cm of wire for the connections.)

2. Begin winding the wire strands around the toroid as seen in the next image.
Please note how the wires are wound correctly:

3. Make 15-18 turns of the wire through the toroid as shown in the next image
above.

4. Connect the two different coloured wire strands from either side of the toroid
and connect them together. Your toroid should look similar to the last figure
above.

Step 5: Construction - Building the Circuit

 (https://cdn instructables com/F9B/F3W4/I

(https://cdn.in
(https://cdn instructables com/FBN/LXUU/IA (https://cdn instructables com/FI1/00BQ/IA

If you are you using the breadboard please examine the images above on where
to place the components. See the circuit diagram in Step 3 to familiarize yourself
with the way the components are connected.#
1. Place the breadboard on a flat surface and gather the transistor, resistor and
LED

2. Insert the transistor, LED and resistor into the breadboard sockets as shown
above

3. Connect the toroid to the breadboard. The twisted wires go to the positive
terminal of the battery

4. Connect the orange coloured wire to the resistor

5. Connect the green wire to the collector terminal of the transistor and the long
lead of the LED (Anode)

Step 6: Conclusion - Working Joule Thief

15 Minute Joule Thief by playmonkey (/member/playmonkey/) in electronics (/technology/electronics/)

Download h (/id/Joule-Thief-Explained/) 6 Steps .  Collection I Made it!  Favorite  Share 

 advertisement

(https://cdn instructables com/F23/SECD/I

If you have connected the components as shown and wired the toroid correctly
your joule thief LED should be shining brightly. Experiment with more turns on
the toroid and/or use a larger ferrite toroid. Happy hacking!!

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Comments

We have a be nice comment policy.

Please be positive and constructive. w I Made it!  Add Images Post Comment

XxelectricmanxX (/member/XxelectricmanxX/) 2015-06-08 Reply

Dude, You have no idea how much I live joule thiefs, awesome instructable! You
should do more!!!!
 playmonkey (/member/playmonkey/) . XxelectricmanxX (/member/XxelectricmanxX/)
2015-06-09 Reply
Thanks :D Joule Thief's are pretty amazing!! Have you
seen the famous Fuji Thief? https://www.youtube.com/watch?
v=EcJG_6YF1X4

blakehx (/member/blakehx/) 2015-08-20 Reply

Is it possible to have too many turns around the toroid? I probably have 25-30
turns of magnet wire around my toroid but can't get it to work with any voltage!
Can't think what else to try! Any help greatly appreciated thanks!

JYon (/member/JYon/) . blakehx (/member/blakehx/) 2017-05-01 Reply

There may be too much power being wasted, as magnet wire is made for
creating a magnetic field, and a magnetic field would drain a bit of power.
Try using a normal wire?

playmonkey (/member/playmonkey/) . blakehx (/member/blakehx/) Reply

2015-08-24
It should not make any difference really, power the JT using a
new battery and see if it works? Otherwise I would re-check all the
connections and especially the way the toroid is wired and connected.
Hope that helps??

Emmanuel2015 (/member/Emmanuel2015/) made it! 2016-07-16 Reply

Fun circuit, that little guy does the job ! I can hear a high pitched sound close to
the coil, looks like about 10 kHz with the scope.

(https://cdn.instructables.com/F7Z/TMKE/IQO23VYQ/F7ZTMKEIQO23VYQ.LARGE.jpg)

playmonkey (/member/playmonkey/) . Emmanuel2015 (/member/Emmanuel2015/)

2016-07-18 Reply
Thanks for building the circuit!! It's a bit annyoing the
high pitched sound. Not sure why it does that?? Core harmonics?

Emmanuel2015 (/member/Emmanuel2015/) . playmonkey (/member/playmonkey/)

2016-07-18 Reply
According to what I found on the web, the frequency is
inversely proportional to the inductance which itself is proportional to the
square of the number of loops. So, if you want to stop hearing that sound,
you might consider lowering the number of loops to have a frequency high
enough to be outside of the hearing range (depends on your age).
 playmonkey (/member/playmonkey/) . Emmanuel2015 (/member/Emmanuel2015/)
2016-07-18 Reply
Thanks that's really interesting!! Potentially could be
used as a low-cost device to test human hearing :) Time to do a bit more
research!!

_Vehner_ (/member/_Vehner_/) 2015-08-02 Reply

I made my joule thief. I made it work with a simple dry run,but after that it
stopped working? Anyone got any ideas?

playmonkey (/member/playmonkey/) . _Vehner_ (/member/_Vehner_/) Reply

2015-08-04
How long did it work for? What voltage is the battery giving? Try
another battery and see if it works?

eyal_hadar (/member/eyal_hadar/) . playmonkey (/member/playmonkey/) Reply

2015-10-05
Worked for five hours.
Although the batteries were not full, instead of 3 volts was 2.5
The light seems incredible that taken to increase the light is weak.
Increased exposure, otherwise the camera does not catch the frequency
of the LED.

eyal_hadar (/member/eyal_hadar/) 2015-06-11 Reply

j.t in work only 2 AA 600 led 10m long

(https://cdn.instructables.com/FKY/B8EV/IAS213BK/FKYB8EVIAS213BK.LARGE.jpg)

eyal_hadar (/member/eyal_hadar/) . eyal_hadar (/member/eyal_hadar/) Reply

2015-10-05
im still checking it

(https://cdn.instructables.com/FQX/BSLI/IFDSTWPB/FQXBSLIIFDSTWPB.LARGE.jpg)

playmonkey (/member/playmonkey/) . eyal_hadar (/member/eyal_hadar/) Reply

2015-06-13
Amazing stuff!!
 eyal_hadar (/member/eyal_hadar/) 2015-06-11 Reply

JOULE thife raning 10W LED FOR MORE THAN 2days,now

Malkaris (/member/Malkaris/) 2015-06-09 Reply

Thank you very much, I've been looking for a well documented explanation of
this device!

playmonkey (/member/playmonkey/) . Malkaris (/member/Malkaris/) Reply

2015-06-09
Thank you, glad the instructable helped :)

DharaniD (/member/DharaniD/) made it! 2015-06-09 Reply

dude awesome. we would. be a partner

(https://cdn.instructables.com/FKO/KUHC/IAPAFYOE/FKOKUHCIAPAFYOE.LARGE.jpg)

Ploopy (/member/Ploopy/) 2015-06-09 Reply

Cool!

playmonkey (/member/playmonkey/) . Ploopy (/member/Ploopy/) Reply

2015-06-09
Thanks :)

pucksurfer (/member/pucksurfer/) 2015-06-09 Reply

Is this how they make it so you can charge your phone with just 1 AA battery?

playmonkey (/member/playmonkey/) . pucksurfer (/member/pucksurfer/) Reply

2015-06-09
 It's not really possible to charge it from a single AA 1.5v battery as most
mobiles need around 500mA @ 5v. As the JT output voltage increase the
current decreases so it may generate 5v there will not be enough current
to charge the mobile. Hope that helps?

XxelectricmanxX (/member/XxelectricmanxX/) 2015-06-08 Reply

Love*

I More Comments

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