(The above video "Hangout with an inventor for #deSTEMber" is the live feed of the National Geographic/Google Science Fair Google + Hangout where NG Emerging Explorer T.H. Culhane shows how to build the Joule Thief and run a superbright LED off of aluminum can tabs and zinc drywall screws, creating the "Solar CITIES Tab Torch" that he used in Nepal on an expedition. The video also shows how to make a homopolar motor and a lemon battery)
On a dark frigid spring night in a frozen mountain pass in the Himalayas, my pup tent covered in snow, 5000 meters above sea level, I lay in my sleeping bag reading a comic book. My source of light? 5 super bright white LED bulbs lit by a chemical reaction between a soda can tab, some wood ash from the Sherpa fire, and a stainless steel scouring pad.
We were on a National Geographic/Blackstone Ranch/Mountain Institute sponsored Expedition to a remote village in the Hinku Valley not far from Mt. Everest, but well off the beaten path, 6 days trek across the steep icy mountain range from Lukla.
Our goal was to share ideas for renewable energy generation with the villagers and help build capacity in the region to help them live sustainably in their homeland even as their forest resources dwindle and the climate changes.
We found that there was already widespread use of solar electric panels thanks to a government sponsored program and the work of many NGOs over the years, but for many families the cost of the panels was still a barrier.
Perhaps worse, the cost and weight of batteries, and the hassle of getting them up the narrow and dangerous mountain passes, made storage of the electricity produced by the few hours of sunlight they received a daunting prospect. And because they need the few small photovoltaic panels they had to keep their own batteries from deep discharge and ruin, they charge the few trekkers who come through on the way to Mera Peak between 3 and 5 dollars an hour to charge their batteries. As a consequence most trekkers brought many non-rechargeable batteries with them for flashlights and cameras, which, once spent, one can find lying scattered along the trail.
The trekkers also are fond of canned sodas and beer, and warm spaghetti, and because of the extreme costs of transporting anything in the region, the aluminum cans and aluminum dinner plate foil only go one way -- up. They get consumed in the lodges and dumped in garbage pits by the river, never to return to Katmandu for recycling.
Looking at the trails in the Khumbu and Hinku Valleys over the past two years through the eyes of the Zabaleen trash recyclers, I began to ask if there was a way to make use of all the discarded batteries and aluminum foil and can waste throughout the region.
After experimenting a bit I found that indeed there is a lot we can do with that 'garbage' because it contains a lot of embedded chemical energy. The key to getting that energy out and making it useful turns out to be the humble "JOULE THIEF CIRCUIT".
A Joule Thief is a very simple thing to build. All you need is:
- A Blue or White LED (Other colors are fine, too)
- 2N3904 Transistor or equivalent
- 1k Resistor (Brown-Black-Red)
- Toroid Bead
- Thin wire, two colors (magnet wire works, .6mm)
- Alligator clips and/or a breadboard
When I did my first build I used the instructions and schematic from the "Evil Mad Scientists" at http://www.evilmadscientist.com/2007/weekend-projects-with-bre-pettis-make-a-joule-thief/
I find their schematic very helpful:
The have a lot of great instructional photographs to show you how to build a Joule Thief step by step, so I highly recommend you click on their link above. They show how to wind the torus with wire. My recommendation is that you cut a piece of double stranded wire about the length of your arm and thread it through the bead and then start wrapping until you have 10 - 12 coils. Twist two of the wires from opposite sides and opposite colors together and that gives you your wire to connect to the positive terminal of the battery of to the stainless steel pad (in the case of an aluminum can tab battery).
The contribution I've made recently to a siimple Joule Thief build is to show people how to do it without soldering, simply using alligator clips. Here is my quick sketch and some photographs of my results:
I use seven different alligator clip wires and use colors to help make it easy to figure out what to connect where. When using a battery I use small circular neodymium magnets for quick connecting of my wires to the battery terminals:
Below is a closeup of the LED bulb wiring:
The black wire coming from the negative terminal of the battery is on the negative lead of the LED and so is a green wire which then goes to the collector on the transistor. On the positive lead of the LED is a red wire going to the Emitter on the transistor, and a yellow wire going to the red wire coming off of the torus bead (opposite the twisted pair).
Here is a close-up of the transistor; note that I refer to it with the flat side facing me and from left to right the leads are Emitter, Base, Collector. Note the white alligator clip wire going to the center of the Transistor, which is the "Base" and acts like a "switch" or a "valve", regulating the current going through the collector and emittor. Think of it as a faucet.
The following image shows that the white alligator wire is connected to the free white wire coming off of the toroid bead. You note that the red free wire coming off the bead goes to the yellow wire which we connected to the positive lead of the LED. You also see that the twisted pair of opposite side red and white wires on the torus bead go to the red allligator clip wire that goes to the positive terminal of the battery.
In the photograph below we see that the white wire coming off of the torus' white wire is connected to a 1 KiloOhm resistor which is then connected to another white wire which goes to the base (center pin) of the transistor.
As you can see from the image below, the completed circuit is really easy to build, and enables one to light an superbright 3V LED from a single 1.5 Volt battery;
The fact that the Joule thief allows one to run a 3V LED from a 1.5 or 1.2 Volt battery would itself be astounding, because it means you only need half the number of batteries to get the same light. That in itself is a tremendous savings (imagine only needing to carry half the number of batteries up to Mt. Everest in your backpack to get the same light!).
But it gets better!
Some of you are thinking "wait, maybe it enables you to use a single 1.5 volt battery to light a 3V LED instead of the usual two, but doesn't it just make that battery last half as long?
Great question, but the answer is that the Joule Thief, which works by building up and collapsing a magnetic field around the torus (which acts as an electromagnetic inductor) actually is more efficient than using a battery directly because it PULSES the energy to the LED. You see the lightbulb shining brightly, but in fact it is turning on and off very rapidly as the magnetic field of the inductor builds up and discharges again and again. That means that though the light appears to be on all the time it is actually turning on and off and saving energy because it isn't on all the time.
But it gets even better: It turns out that the Joule Thief enables the battery to keep supplying electrons to the light long after the battery is normally considered DEAD. So the battery actually lasts much much longer than a normal battery. And for this reason, in Nepal I was able to pick up dead batteries that tourists had thrown along the trail when they no longer ran their cameras, and use them to run my flashlight!
I've observed "dead" batteries working down to about 0.5 Volts. Normally a 1.5 V battery is considered dead when it reaches 1.0 volts. But the Joule Thief can "steal" the remaining energy much below that.
And that got me thinking -- could I use other sources of between 0.5 and 1.0 Volts to run a 3V LED?
I was experimenting with aluminum garbage and a solution of lye made from wood ash from the Sherpa's fire (Potassium Hydroxide, used to make soap in the old days) to create hydrogen (a chemical reaction I knew about and used to show my students dating from when I taught Chemistry at Marlborough High School in 1989!). Hooking a voltmeter up to the reactants to see what was going on I observed a voltage during the reaction of between 0.5 V and 0.9 volt. So I lowered my concentration of lye to keep the hydrogen bubbling to a minimum and hooked everything up to a Joule Thief.
The reaction was astonishing -- I was able to light the LED to full brightness, just from one coke can tab and a piece of stainless steel. I had, in fact, created an aluminum oxide battery. And I found that I could light not just one LED from this simple procedure, but 5, all super bright!
This meant that no matter I went in the world, as long as I had some aluminum can tabs in my pocket and could gather some hardwood or fruitwood ash from a fire and had my joule thief, I could run a flashlight indefinitely, never needing to worry about batteries again! Each aluminum can tab lasted me up to 6 or 8 hours before needing to be replaced.
Here are some pictures of the reaction, using drain cleaner fluid (sodium hydroxide) as the source of lye:
I call this invention the "Solar CITIES Tab Torch" because it is a flashlight (Torch) that runs on Aluminum Can Tabs. It will work on aluminum foil and aluminum yoghurt covers too, or aluminum dinner plates. But if you don't have aluminum, don't worry, it also works with Zinc -- so you can carry around a pocket full of drywall nails too, or plumbing pipe, or a bit of your zinc roof:
So the Joule Thief, coupled with my discovery in Nepal of the voltages I could produce from scrap aluminum or zinc and wood ash-based lye, now enables anybody in the world to light their world from garbage.
And that is why, as I sat in my tent all those frigid nights in the most remote areas of the Himalayas, I was never worried that I would run out of light, no matter how dark the days and nights, come rain or shine, so long as I had a source of garbage and ashes -- things we never seem to run out of no matter where we are in the world. And that is why I could spend my time and energy reading comic books, rather than worrying about where the next civilized outpost was where I could buy batteries.
Electricity is all around us, and through the eyes of the Zabaleen, you can see it everywhere, if only we can, as the song goes, "look beyond the garbage in the streets to see the garbage in our minds", mental garbage that prevents us from seeing that everything we need is often already right in front of us!