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Our latest Weekend Project, the Solar USB Charger, could easily be our greatest yet! This hack really encapsulates a lot of what Weekend Projects is all about. It's simple, requiring a relatively small amount of components and solder joins. It's useful, because whenever the sun is out, you have a free charging station. And it's resourceful, converting all those excess USB cables you have into something useful again. It also has an "Aha!" factor, as the visible tech – solar cell and USB cable – is recognizable to most people these days, but to combine them together in this way will impress anyone new to the field of electronics.
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All you need are these parts and a USB cable |
A hack so simple it's cute! |
The Zener diode is what makes this possible |
Testing our solar USB charger on a sunny day |
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5V of Simple Solar Power
The component that allows us to convert this 6V solar cell into a rockin' Solar USB Charger is the 5.1V Zener diode. Similar to the rectifier diode which we also use in this project (and have used before in our Solar TV Remote
), the Zener diode allows current to pass in the forward bias. However Zener diodes are also specifically designed to have a controlled reverse-bias breakdown, maintaining voltage across the diode at a value close to its "Zener voltage" – in this case 5.1V – ideal for USB applications, whose standard is rated at 5V±5%.
Diodes and Diode Symbols
The 'S' or 'Z'-like shape in front of the arrow lets you know this is a Zener diode on circuit schematics. While all of the above symbols are technically correct, what matters most is remembering that the shape in front of the arrow corresponds to the painted line or stripe on the diode package. This line represents the cathode, or negative end of the diode – and remember with Zener diodes, the current of interest is the reverse current. In the above image you can see (top to bottom) a rectifier diode, a signal diode, and a Zener diode. Note the lines or stripes on the right side of the diodes: this is the diode's anode.
Watch the Zener Work
It's always a good idea to test your circuit before any real-world applications, so check out how in this video from Steve Hobley showing the Solar USB Charger in action! Once completed, this project is guaranteed to impress anyone who never knew this was possible. After all, with this hack you can power or charge any 5V USB device with the sun! How cool is that? Of course how many milliamps you draw will vary, and remember this is a real-time power output device since there is no battery involved. So send us a quick story about your application and photos of your sun-powered USB mod. You can always contact us via email
or on our Facebook page.
And the Winner Is!
Last week on Makezine we asked you to tell us a story about your first encounter with electronics. In exchange, one story's author would win a Mintronics: Survival Pack along with a Maker's Notebook
. Among other things, we learned: that radio was a lot of makers' first encounter with electronics, that some makers thought their DC projects could plug directly into AC outlets, that moms are vital components to some projects, and that a trip to the local RadioShack store rings dear to the hearts of many, old and young. All of the stories are wonderful, and you can read them in the comments here.
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