Introduction: Single Cell, White LED Torch Fits in a Matchbox

A little while ago, Makezine blog listed two interesting sites: HOW TO - Make a rusty nail LED night light and ELM - AVR based radio spectrum monitor.

Chan has a great site and he has put up a lot of interesting projects, incidentally many of them based on AVR. One of his projects (not based on AVR) is a pocket LED light. He describes a blocking oscillator based single cell, white LED torch. This and rusty nail project got me thinking and I started experimenting with Chan circuit. The circuit is very robust and it worked with a wide variety of transistors; I tried BC547, 2N2222 and 2n3904.

But the real fun and challenge was in building an enclosure for this torch. I have been a big fan of matchboxes; as a kid I used to collect empty matchboxes everywhere I went. I thought the art on matchboxes reflected the local culture.

Long ago, I built a data logger that could fit in a match box (I never completed it in that form, settling to find a much larger enclosure). But now I was determined to fit the white LED torch circuit AND the AA cell in a matchbox.

Step 1: Build the Matchbox Tray With Pieces of PCB

I took a fairly large matchbox and threw away the tray and decided to build my own tray using a technique I had learnt as a radio Ham: to use pieces of PCB and to solder them together to make a faraday cage of any size. I cut three pieces of PCB. I Drilled a large hole to accommodate the 10mm LED in one of the PCBs.

Step 2: Make a Cutout for the Switch on One of the Side Walls of the Tray

On another PCB, I made a cutout for the On/Off switch as seen here. The body of the switch was bent and soldered to the PCB so that it was secure.

Step 3: Another View of the Switch Soldered on the PCB

Another view of the switch soldered on the PCB.

Step 4: Solder the Three PCB Together

Solder the three peices together to make the matchbox tray. To solder, start by applying solder on the edges of the PCBs and then align two pieces and apply soldering iron. You may need to hold the solder iron for a little while so that the solder melts nicely. Dont move the PCBs till the solder has cooled off.

Step 5: Solder Components and Add a Side Wall to the Tray

Take another piece of PCB for the side wall of the tray. I used hobby drill to create islands of copper on the PCB. Solder the components on the PCB as per the circuit diagram in the next section.

Step 6: Circuit Diagram

This is the circuit from Chan's website (http://elm-chan.org/works/led1/report_e.html) which I modified and hived off two components. The modified circuit is seen here. The circuit is very robust and it worked with a wide variety of transistors; I tried BC547, 2N2222 and 2n3904. The coil I used had 25 turns each, of 26 gauge wire. Resistor R1 changes the intensity of the light. I tried values between 2KOhm to 220Ohm and I settled for 220Ohm. The light is quite bright at this value.

Step 7: Add the Final Side Wall and Fix the 'AA' Cell

Finally, add another PCB for the last side wall. For the cell, I cut a piece of holding spring from an unused cell holder and soldered it on the left wall of PCB in the picture and this forms the negative terminal of the cell. To isolate the positive terminal of the cell, I again cut an island on the right hand side of the PCB and soldered a wire to the switch as seen in the picture.

Step 8: Slide the Tray in the Matchbox Cover!

This completed tray slides in nicely in the matchbox cover. If the tray doesnt slide in smoothly, file the edges that may be obstructing.

Step 9: And Switch It On!

Just switch it on! And enjoy.

Comments

author
shopw (author)2015-12-01

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author
shopw (author)2015-12-01

Thank you for providing me a informative blog. I enjoyed it thoroughly, it helped me a lot for what i was searching for. Keep it up. You do very good. For more details about building materials Visit: http://www.msbmgulf.com/product/gi-binding-wire/

author
BOOJAN (author)2011-01-03

daaaamn, nice box, i havent thought about this kind of box for the joule thief...nice instructable mate :D

author
king2010 (author)2010-07-30

As i am not good in electronic, could any one help me making the coil? whether i need to make 2 coils or the ferrite material will have the terminals? what indicates the 2 "dots" in the circuit diagram.

author
thulasidas (author)2010-07-26

Simple and easy circuit. Please help me to make the coil. What is the name of the "Black part" in which coil is present,

author
Gadre (author)thulasidas2010-07-26

Its a ferrite former on which the coil is wound. You could use ferrite material in any shape such as a dumb-bell or a toroid.

author
Sunil-VU3SUA (author)2010-01-10

Good Project.
I could offer this as a kit very soon with a small plastic case like a match box and with all components. I would make one myself soon and post the link with pictures soon.
Thanks and well done
Best Regards
Sunil
http://cqbitx.blogspot.com

author
imakethings (author)2009-04-08

can it work on voltages less than 1.5 volts?

author
imakethings (author)2009-02-13

is it a step up transformer? or a joule thief?

author
WardXmodem (author)2008-06-29

I made one - using one of about 10 toroids I bought - about 1cm diameter; then today I took apart some old equipment to salvage and found a 1" toroid. It didn't work as well. Anyone know if you should interleave the turns, or make them more like a transformer "picture", i.e.. one coil on one side, and one on the other? The larger one worked but drained the battery almost like a short - I'll have to double check my wiring. P.S. I am using one of those multi-socket breadboard things, and made a trick of taping my 4 coil leads as they exit the socket, so I can unplug and replug it (or change to another coil). Cheap plug! haha. I'm going to try "going crazy" with this, I bought a "bag of ferrite beads", from eBay, I hope they are big enough to get the 20-25 turns through.

author
WardXmodem (author)WardXmodem2008-07-19

The ferrite beads I bought are Outer Diam: 0.15"(3.8mm), Inner Diam: 0.059"(1.5mm), and I could only get about 4 turns (each, 8 total) of 30ga. wire, but IT WORKED!!!!!!!! I then, through eBay, bought various sizes, and found I could get about 8 turns (16 total) of #33 wire, and that worked even better. THEN since this is called a "Joule Thief", I decided to make it more of a PUN, namely that a "jewel thief" would only work in the dark. SO I changed the 220 ohm resistor to a 10 turn potentiometer, and saw how far I could go, with a phototransistor pulling it down to ground. A 20K ohm value turned out to be correct, and now a blue LED will only light if the room is quite dark. NOTE I have perverted the original design from a bright flashlight kind of thing, to a smaller "marker" light with extremely long battery life, i.e. in a very darkened room where you might bump into something, you can place one of these like ships use light houses to avoid piers, etc. If someone wishes to write to me as WardXmodem at my Yahoo address, I would be willing to ship a tiny bead and a foot or two of #33 wire, so you could make one. NOTE these are tiny, you need steady hands and good eyes. If you want me to put together "everything" - a transistor, an LED, the coil, and a resistor, let me know, this stuff doesn't cost much at all. I reserve the right to NOT respond to requests should I get overwhelmed or any other good reason.

author
Gadre (author)WardXmodem2008-07-19

Could you please post pictures of your creation? Thanks,

author
WardXmodem (author)Gadre2008-07-19

It is just on a socket board at this time. I'm trying to figure the best thing to "make it into", perhaps a twist-off plastic bottle cap? I also have some "Lumalite" ivory colored casting resin, etc. The toroid is so small and the wires so fine, other than just direct soldering to say transistor leads, I'm trying to figure a way to "mount" it. Perhaps just a tiny dab of hot melt glue on the transistor to hold it in place ;-)

author
Gadre (author)WardXmodem2008-07-19

Congratulations! Good Job...

author
hmms (author)2008-01-16

take a look at my led torch! the case is made from the packaging bax tht my chamelion ni-mh batteries came in!

P1010133.JPG
author
microman171 (author)2007-04-01

for some reason niether of the versions I tried are wokring (ver2: Make A Joule Thief Why is this?? Nex im going to try it on a rusty nail. I even tried tapping it with the cap to make it work but that didnt work. Any Ideas?? I am useing an NPN transistor (BC548)

author
hmms (author)microman1712008-01-15

dude i had the same prob. i suggest u to interchange the connections of the coil . it will surely work!!

author
microman171 (author)hmms2008-01-16

Tnaks!! next time im into this ill try it again!

author
Gadre (author)microman1712007-04-02

The important point is the way the coil is made and connected. I suspect that your coil may not be connected properly.

author
microman171 (author)Gadre2007-04-02

Are you sure?? I have make 3 coils... The joule thief one the rusty nail one and your one. Thanks for helping me out btw. I found the it outputs 2.4v AC...???

author
hmms (author)2008-01-14

pls tell me where can i get the core of the inductor???

author
acaz93 (author)2007-04-14

just for curiosity do you know the value of the coil in henries?

author
stone3408 (author)2007-04-02

Great job! Very simple very effective.

author
Tool Using Animal (author)2007-04-01

excellent, i saw the rusty nail blocking oscillator and think this is an brilliant extension.

author
skids927 (author)2007-03-31

Isn't a battery, resistor switch and bulb a little bit easier? what is the point of the extra coils and stuff? Im not trying to put you down, it turned out nice, I am just curious.

author
Gadre (author)skids9272007-03-31

The bulb would drain out the battery quite rapidly. A white LED on the other hand lasts longer, but requires a voltage of 3V or slightly more than that for operation. That is where the coil, transistor and resistor come in. These three components make a very simple step-up DC-DC converter which is suitable to drive the white LED.

author

isn't the coil thing a home made capasiter? (somthing that builds a electric charge? (i think)). Im kinda a new at electronic stuff so could you show a little more detail in the coil, please?

author

Actually a coil is the so-to-say opposite of a capacitor, while a C stores electric charge and so build up a voltage, a coil stores current and by altering the potential via the Transistor, you set the potential of the upper end of the coil free so that the charged current has to flow through the LED while building up the needed Voltage. You see almost the same concept in engine ignition if the LED would be an Air gap you might even see a tiny little spark. Any given current will theoretically build up a infinite Voltage for a infinite Resistor (Air-Gap) U=R*I. Of course the given circuit isn't made for sparks.

I love the simplicity of the implemented circuit.

author
Visitor (author)2007-04-01

The character encoding you use seems to be broken. There is "garbage" between words "Chan s circuit" and "1.5V cell". Please fix. Thank you.

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