I recently stumbled upon Akimitsu Sadoi’s website, The LED Artist. Akimitsu describes himself as a Brooklyn, NY based electronic artist with the motto “Art and Technology are Friends”. He designs and builds LED Art projects and offers a variety of kits for sale through his online store. I’m a sucker for anything that lights up, so it didn’t take me long to find several kits I wanted to purchase and build. I can’t afford to buy every kit I want on there, but I did pick up a couple, the smaller (and cheaper) of which is the Colour Night Joule Thief.
This kit is based on the original Joule Thief project at bigclive.com, which in turn is based on a circuit included in the magazine Everyday Practical Electronics. For detailed information on how it works, I suggest this tutorial which includes a schematic, details on the parts used and explanation of the circuit’s operation. The simple explanation is that the Joule Thief is able to to get the last bits of power out of 1.5v batteries that might otherwise be considered “dead” by other devices and light up an LED. It sounds amazing, but surprisingly it does this using a minimal number of components.
The Colour Night Joule Thief has more components than the original, but it does a few things it doesn’t. First, it utilizes a photoresistor to detect light, so it can turn on automatically when it’s dark, making for an effective night light. The sensitivity is adjustable. The other big difference is the use of a color-changing LED, which makes it a little more exciting than a plain white LED (though, if you want a plain white LED, consider the Night Joule Thief kit). There are other technical differences (different induction method, extra circuitry to rectify the output for the color-changing LED) but the component count is still fairly low. This is an ideal kit for beginners wanting to learn how to solder.
Assembly is quick and easy using the information found on the Instructables page for the project. The only issue you may run into is keeping diode D1 from contacting with the negative battery clip. The instructions point this out and advise you to cut the lead on D1 short to avoid a short circuit. I cut the lead as short as I could, but it still seemed too close to me. I opted to insulate it with electrical tape to ensure there wouldn’t be a problem. The board layout is pretty tight, but it would be nice if the clip and diode were laid out further apart.
The finished kit worked great with a brand new battery and a small adjustment for light sensitivity. Of course, the whole point of a joule thief is to use it with spent batteries taken from other devices that can no longer use them. I didn’t have any really dead batteries, but I did have some NiMH AA rechargeables I had pulled from my wireless keyboard but hadn’t got around to recharging yet. They were at about 1.16v, and the joule thief worked perfectly with them. According to the Instructables page, the circuit should work down to about 0.6v.
Despite one small issue with the layout, it’s a quality kit – easy to build, works as expected and looks cool. I think that anyone learning to solder for the first time would enjoy it, especially children. The complete Colour Night Joule Thief kit is less than $11 and can be purchased from The LED Artist or the Maker Shed.