Whether you're heading into the woods or navigating an urban jungle, stay charged with this easy-to-build solar charger.
Tap into the sun's sustainable rays using Digi-Key parts, a circuit board, and some basic DIY tech know-how to keep anything you can connect to a USB powered for hours* - or at least until the sun goes down.
Small slotted screwdriver
Time Required: 1-3 hours
*The charger can only supply a maximum of five (5) volts @ 500mA in direct sunlight.
**The complete instructions are essential to this project.
Step 1: Prepping the Prototype Board
Prep the prototype circuit board: Trim it down, file the rough edges and drill the mounting holes
Step 2: Circuit Assembly - Placement
Assemble the circuit and solder components into place
Step 3: Circuit Assembly - Connections
Interconnect the components
Step 4: Enclosure Preparation
Modify the enclosure and mount the board
Step 5: Final Wiring & Testing
Do the final wiring and test. Make sure the positive and negative sides of the solar panel are connected correctly.
This is a nice project, but it's worth mentioning that you're only pulling 2.5 watts off a 10 watt panel! Ideally, a higher current converter could be specified, and more USB connectors.
In my lab, using my coworkers' phones as test dummies, hooking up to a bench supply with digital current meters, I've found that cell phones want anywhere from 0.25 to 1.2 amps for charging. My BlackBerry will give up with a stupid message if it tries to pull full charge current and finds it's able to dip the supply.
Just out of the interests of, I dunno, SCIENCE... The Parallax solar panel appears to be a monocrystalline with Suntech cells. They're pretty good, but $6.38 a watt is awfully steep pricing. The same voltage converter will work with any panel that puts out up to 32 volts DC... Look for a open circuit voltage - Voc - of 32 or less, and maximum power point voltage Vmp of 6 or more. If the seperate Voc and Vmp figures are not given, it's fairly reasonable to assume the specs are stating Voc.
Thanks for the post, especially the lab current measurements . Many of the things you mentioned were discussed at length in a previous post under the "Power Solutions Community."
The "Energy Harvesting Community" is fairly new. It didn't exist when the person at the above link posted his question in the power community, otherwise he probably would have posted it here instead.
Message was edited by: Alec
Watch out, the peak current during transmit can be in the amps. A long time ago I did a switching converter for a Motorola IDEN cellular modem. Worked fin here in Baltimore but only because there was no IDEN service at that time. Wen it got to Atlanta if found service and tranmitted to the tower. Supply crash and reset. 3.5 amp peak.
I'd like to add a few more steps to make this a more portable system:
STEP 6. In your attic, find your college graduation cap (mortarboard).
STEP 7. Attach 320 x 280 mm solar panel to the top.
STEP 8. Wear proudly to your next IEEE meeting!
Message was edited by: Richard_Comerford_Editor_Electronic_Products