Want to learn to create a fully solar powered speaker? Then this Instructable is for you. If you like what you see feel free to vote for this project for the Audio contest. Thank you!
Step 1: Select Your Speakers!
Find some speakers or order some to work with. This system utilizes a subwoofer (Teac), 4 midranges (Boston Acoustics), and 2 tweeters (Boston Acoustics). All were sourced from garage sales for about 20 bucks total and originally came from higher end desktop computer sound systems that were broken.
Step 2: Design an Enclosure
Next you will want to design an enclosure for the speakers. This will of course have to accommodate your solar panel and electronics as well which will be covered in the next steps. Use MDF as it is cheap and performs well for acoustic applications. In this design, the electronics were compartmentalized from the acoustic chamber. Another consideration is box volume for the speakers. For my project I simply added the volume of the individual donor speakers and placed the separating panel accordingly. For even better results, you may wish to separate the subwoofer from the mids and tweeters.
Step 3: Create Your Solar Panel
Choose the solar cells you would like to use for the project based upon a couple of considerations:
1) Try to aim for an 18 volt panel to supply to a 12 volt battery
2) Attempt to make a panel that will supply a reasonable amount of amps to keep you speaker running continuously. The panel used in this project is able to provide about half of the max amperage that the amplifier can draw. This is acceptable as the draw of an amplifier is far from constant and will often only be a fraction of its highest draw in any song. In testing, the speaker was able to run continuously for 9 hours on a sunny day and remain charged the whole time (starting from a lightly charged battery).
Once you have chosen the cells, you will need to solder them together and encapsulate the cells. In this Instructable I used EVA film, a relatively easy to use material. To make the panel follow these steps:
1) Apply flux to a cell and slide a soldering iron across the cell with a piece of tabbing wire. Once cooled be sure to check that a strong bond has been made. This takes much practice to get right. By file a flat spot in the tip of your soldering iron you can make this process easier. I used a 30 Watt Harbor Freight Iron and found it to provide a perfect amount of heat for the job.
2) Flip the cells over and solder them to each other in lines. Be sure to keep in mind that you are creating a circuit. It usually takes 36 cells to get an 18 volt panel, you will want to wire them in series to achieve this.
3) Solder the lines together at the ends.
4) Prepare a piece of glass (in this specific project, I applied the cells directly to the top of the speaker, however, if a mistake were to be made it would be better to have the cells on glass for easy removal).
5) lay down a piece of EVA film larger than the glass by a few inches on each side.
6) Place your cells over top of the glass
7) Place another sheet of EVA film on top.
8) Use packing tape and a spare piece of wood or MDF to tape the glass, EVA film, and cells to. Leave a spot for a vacuum hose.
9) Use your household vacuum cleaner to pull a vacuum on the cells.
10) Use a heat gun to permanently seal the EVA film to the cells. Heat until they are clear.
Step 4: Electronics Design and Testing
Design an access panel to mount boards on. See the labelled picture for what to include. You will want to do some research on what amplifier will properly power your speakers. Not pictured is the ac to dc inverter (originally I placed it inside the access panel, I have now taken it out as it was back feeding from the battery). The labelled picture is not wired to make it easier to view. Now is a good time to test out your system as a whole and make sure it works properly. For this project I used a 12 volt 5 amp hour battery which gives the system very a long battery life. You will need to calculate the proper size of the battery for the size of your speakers and amplifier.
Step 5: Finish Line!
Mount your electronics panel and speakers. Be sure to design some sort of top cover that rests above the EVA encapsulated cells (not on). I made a simple plexiglass cover for this. You will also want to add a speaker grille to protect your hard work. I used some left over wood scraps to fit a grille into the recess on the front panel. Thank you for reading and feel free to ask any specific questions about the project!