Introduction: Solar Powered USB Charger

Picture of Solar Powered USB Charger

Hey, our names are William and Rajan, and we are high school students from Fremont, California. We're students from Ms. Berbawy's Robotics Class. We have created this project in a well-equipped Maker Space in Ms. Berbawy's classroom.

All credit for the project idea, material sourcing, and wiring diagram go to Bartletts Workshop in Electronics. You can find him here.

Special equipment you will need includes:

-3D printer

-Rotary Dremel with assorted tips

-Wire cutters

-Wire strippers

-Measuring tool (ruler, measuring tape)

-Hot glue gun

-Soldering iron

-Pliers

-Needle-nosed pliers

The consumable parts will be listed in the next step.

Step 1: List of the Parts

Picture of List of the Parts

Step 2: Creating the Charger Box

Picture of Creating the Charger Box

You'll need access to a CAD software--we personally used tinkercad.com as it's free and has all the features you'll need to create your USB charging box. Once you've registered for an account, create a new blank project.

1. The first step is to select the box hole tool and drag out the default cube shown in the first picture. While the piece is still selected, change the form from hole to color in the inspector menu. This will make sure that the 3D printer recognizes your piece as a solid object to be printed.

2. Change the length, width, and height of your first piece to the desired dimensions for your solar panel size and continue shaping the rest of the pieces to form a complete rectangular prism that fits the dimensions of your solar panel. (TIP: You can modify the grid size for more precise measurements. Do this with the 'Edit Grid' option shown in the second picture)

3. Ensure there is enough room inside the cube to fit the battery and the wiring.

4. After you've shaped all of your pieces, you'll need to create holes for the switch, the micro USB charging module, and the standard USB size battery converter step up module. Do this by repeating Step 1 while leaving the piece in the hole form.

5. Drag each hole into your desired spot. The holes for the micro USB charging module, standard USB size battery converter step up module, and the switch must be fitted onto the side panels. It is up to you which panels receive these holes.

6. You need to create one more hole which will be placed on the top panel where you will need space to wire the solar panel through to the rest of the electronics. Outline a hole the size of the two marked solar panel solder joints of the panel and fit it where you would like.

6. Each of your pieces should look something like the final picture. The next step is to group each hole and solid piece together so TinkerCAD will treat it as one solid. Do this by selecting both pieces and selecting the group option shown in the top bar of the third picture. Do this with each of the box pieces.

7. The final step is to navigate to the 'Export' menu. From here, select the option labeled 'Download for 3D printing' and highlight your desired box piece. It is important that you only select one piece at a time to prevent issues with the 3D printer.

8. Once downloaded, export the box file in the .stl format to a USB and transfer to a 3D printer of your choice.

Step 3: Glue Together Most of Your Box

Picture of Glue Together Most of Your Box

1. Construct your box by first squirting hot glue onto one of the two selected pieces you will glue together. Glue together all of the box panels except the top panel.

2. At this point you can also glue the solar panel onto the top panel by applying hot glue to one of the objects. Be careful that the solder joints align correctly with the fitted hole of the box panel.

3. Place the switch into its respective hole. Use hot glue to secure it in place if necessary.

Step 4: Wiring 1

Picture of Wiring 1

Your wiring for this project should follow the circuits in the wiring diagram above. The red wires should be the same positive red wires in your electric circuit and the black wires in the diagram should be the same ones as your negative black wires.

Credit for this wiring diagram goes to Barletts Workshop. A link to his page is attached at the introduction and the end of the instructions.

1. Begin by soldering a red wire to the positive joint of the solar panel and a black wire to the negative joint of the solar panel. You will need to strip off the insulation from each end of the wire, but do not strip off more than one centimeter. Exposing too much wire increases risk for short circuiting the charger and blowing up the LIPO battery. Keep these wires around 7 inches long because it's easier to make sure you have room for everything now and cut excess wire later.

2. Solder the positive end of a rectifying diode to this red solar panel wire. The positive and negative sides of the diode should be marked in the plastic part in the middle.

3. Solder the other end of that diode (negative) to terminal labeled IN+ on the mini USB charging module. This terminal is located at one of the corners.

4. Solder the black panel wire to the terminal labeled IN- on the mini USB charging module. This terminal is adjacent to the IN+ terminal.

Step 5: Wiring 2

Picture of Wiring 2

1. Solder one end of two new black wires together and one end of two new red wires together.

2. Twist each set of wires until only half of each wire is still exposed. Your result should look like the double wires shown in the photograph.

2. Solder the soldered end of the double black wire onto the BAT- terminal of the mini USB charging module. This terminal is located at one of the corners of the module.

3. Solder the soldered end of the double red wire onto the BAT+ terminal of the mini USB charging module. This terminal is adjacent to the BAT- terminal.

4. Solder one of the open wires of the double black set to the black wire protruding from the lipo battery. Tape this connection with electric tape.

5. Solder one of the open wires of the double red set to the red wire protruding from the lipo battery. Tape this connection with electric tape.

IMPORTANT: The black and red wires and any connections to them must never come in contact. This would short-circuit the lipo battery and create a hazardous explosion.

6. Solder the remaining open wire of the double black set to one pin of the switch.

7. Solder the remaining open wire of the double red set to the IN+ terminal of the USB booster.

8. Connect the IN- terminal of the USB booster to the remaining pin of the rocker switch with a black wire. The wiring is now complete!

Step 6: Finishing Construction

Picture of Finishing Construction

1. Place the mini USB charging module into its respective hole. Secure with hot glue.

2. Place the USB booster into its respective hole. Secure with hot glue.

Step 7: Charging

Picture of Charging

There are two main ways to charge your phone, both of which require the switch to be turned on.

1. Leave the device out in the sunlight for energy to transfer from the solar panel to the lipo battery. Plug in USB of selected charger into the USB booster port. Charge as desired.

2. Manually charge your lipo battery by plugging in a mini USB into the corresponding port and charge lipo battery individually as desired. Plug in USB of selected charger into the USB booster port. Charge as desired.

All credit for the project idea, material sourcing, and wiring diagram go to Bartletts Workshop in Electronics. You can find him here.

Comments

hemaraj (author)2017-05-12

what is the rating of solar panel and battery. and how you calculated to match battery and panel.

Swansong (author)2017-05-10

That's neat :) I would love to have something like that to take with us camping.

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