Friday, June 22, 2012

How I built a Solar iPhone Charger for under $50.

How I built a Solar iPhone Charger for under $50.
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I am not responsible for any damage that you may cause to your iPhone or any device that you use with this charger. I can not stress the importance of checking your circuits with a multimeter enough, and I can assure you that I've done so at every step in this build process. Your phone is a very expensive device. Treat it like one!

Intro and Design:

Over the past month or so, I've been working on designs for a stationary solar iPhone charger. By stationary I mean a charger that will be kept in a fairly permanent place. I bring mine with me if I'm going to be camping or staying somewhere for a while, but it's really not meant to be portable.

This isn't only a solar iPhone charger. You can use it with any device that will charge via USB. I just happen to use it to charge my iPhone. Also, this design doesn't include a battery in the circuit - which means that you'll have to charge your iPhone when the sun is out and shining. I know it's a serious inconvenience, but adding a battery makes the circuit much more complex - and is a bit more costly. I'll be following up this design with an update on how to add a battery conveniently into this circuit.

The idea behind this panel is that it's simple (and cheap!). You don't have to have any prior circuit knowledge,or familiarity with electronics. I'm really just stepping out of the novice stage as far as soldering is concerned, so this is a great beginner project for just about anyone!

Step 1Tools and Materials

As I say in the title, I built this charger for just a bit less than $50. That doesn't include the cost for tools and a few of the materials that were salvaged, but if you spend enough time on eBay you should be able to build yours for the same amount, if not less.

Let's take a look at what was used to build the panel.


Soldering Iron w/ Solder and Flux
Needle Nose Pliers
Wire Cutters/Stripper
MultiMeter (IMPORTANT)
Materials and Prices:

Part/Material ------------------------------------- Source ----------------- Cost

10 Watt Solar Panel ----------------------------- eBay -------------------$41.45 w/ shipping
7805 5Volt Regulator ---------------------- RadioShack ------------- $1.59
iPhone/iPod Cable ------------------------------ eBay ------------------ $1.20
USB Extension Cable -------------------------- eBay ------------------ $3.00 w/ shipping
Red/Black small-guage wire --------------- On Hand --------------- Free
Electrical Tape --------------------------------- On Hand --------------- Free
Small Zip Tie ----------------------------------- On Hand --------------- Free

Step 2The Panel

  • SolarPanelFront.jpg
  • SolarRatingSticker.jpg
  • Amperage Reading.jpg
  • Voltage Reading.jpg
This Solar Panel is a 10W panel made by LaVie Solar. You can check out their website, but your cheapest bet is to use eBay. Their eBay user ID is lavie-inc. I snagged a pretty great deal at $41.45. The panel has a really sturdy build quality. It has an aluminum frame, and seems to be entirely weatherized. I wouldn't have too much of a problem leaving it in the rain. Also, All of the wiring has been done for us which saves a LOT of time. They even put a blocking diode into the connection on the back, so we don't have to worry about that in our circuit.

The panel has an output rating of 21.6 Volts (Open Circuit) and .62Amps (Short Circuit). These are optimal ratings, but when I tested my panel in direct sunlight, that's almost exactly what I got.

As far as efficiency goes, this is not the ideal panel to be using as a direct USB charger. We'll be loosing a lot of energy as heat when we regulate the 20V output down to 5V to match USB standard. However, using a larger panel means that there will be more current flowing even when there's not a lot of sun. I've even seen my iPhone charging when the solar panel is in the shade!

Step 3The Simple Circuit

  • DirectionDiagram.jpg
  • CutWires.jpg
  • 7805BagBack.jpg
After gathering all of the materials, I sat down and got to work.

I cut 2 pieces of Black wire and 2 pieces of Red Wire. The lengths were around 5-6 inches. Then, I cut a little bit less than an inch off both ends of each wire.

With my black and red wires ready, I cut my USB extension cable in half and stripped the cut half of the female end to expose all of the individual wires. There are 4 wires in all USB cables- Green, White, Red, and Black. The Green and White wires are for data, so those are not needed. I snipped the Green and White wires, along with all of shielding and fiber - leaving only the Red and Black wires coming out about an inch and a half from the USB cable. I stripped a little bit less than an inch off the Red and Black wires on my USB extension.

Since the 5V regulator only has one Ground pin, I used the two black wires that I cut initially- to make the soldering a little bit easier. I took both of my black wires, along with the black wire coming from my USB extension, and twisted them all together carefully and securely. I put some solder on that connection to make sure that all of the wires stayed together. Then, to keep things safe, I covered the 3-way connection with electrical tape.

Once all of the wiring was prepped, it was time to put the 5V regulator into the equation. Soldering wires onto the tiny pins from the 5V regulator can be a task. I used a small Zip Tie to hold my wires to the 5V regulator to make things much easier. It really helped - I was able to do pretty clean solder jobs on each of the pins. Since neither of the red wires were connected to anything, it didn't matter which ones I soldered to which pins. Just make sure you know that if your 5V regulator is laying flat, the input pin is on the bottom, and the output pin is on the top!. I also bent the pins in opposite directions to keep everything separate.

The fantastic part about this charger is that we're already done with our circuit. Once I was done soldering to my 5V regulator, I connected the Red wire from the Output pin on the regulator - to the Red wire coming from my USB extension cable. Now, I only had 2 wire ends left. A Red wire connecting to the input pin on my 5V regulator, and a Black wire connecting to the regulator's Ground Pin and my USB extension cable.

Step 4Connect the Circuit to the Panel

Since the LaVie Solar Panel has a pretty simple connection panel, pinching the Black and Red wires to the right screws on the panel was easy!

Step 5Test the Charger!

  • SolarPanelBack.jpg
  • iPhone Charging.jpg
I used my MultiMeter to measure my Input voltage that was going into my 5.00V regulator. about 20V @ 0.50A Good!. Then, I measured the output voltage coming from my Regulator. The reading was 5.00V @ 0.50A Perfect!. Those readings meant that everything was working correctly. Watch out, that 5V regulator gets hot when electrons are flowing through it!

Fully convinced that everything was working as it should be, I covered all of my open wires with electrical tape, took a deep breath, and plugged my iPhone in.


Step 6Conclusion

In future designs, I'll definitely be adding a battery so that you can charge your devices at a more convenient time. I'd also like to make a more portable version of this charger. With all of the new solar technology, flexible panels are bound to cheapen up sometime!

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