Solar-Powered Piano Keyboard

Musicians have put actual pianos in a field and play beautiful music amidst the sunshine and birdsong. I don't own an actual wood & strings piano, but I do have a digital piano keyboard - and I can easily load my keyboard, battery, and solar panel into my small car, and take the music wherever the road goes and the sun shines. You can too! And if you do, please send me photos...!

EDIT: Many digital pianos out there already can be powered off a large number of alkaline C or D size batteries -- for most of you, that may be the cheaper option! Building this system, however, gives you recharging-while-playing capability!

The main components you need to make your own solar-powered piano keyboard are:

• a digital piano keyboard that takes a 12VDC input -- check the back of the power adapter that plugs into your keyboard - it should have two lines that tell you the input voltage and current, then the output voltage and current. Please see photo above of the adapter for my piano: the input voltage is 12VDC, and the input current is 1.5A. My keyboard is a Casio CDP-120.
• a 40-50W solar panel -- I'm using an older 40W Kyocera mono-crystalline panel, but any 40 or 50W panel would be sufficient, and there are a lot out there that are MUCH cheaper. You can use a larger panel if you want, just make sure its max output is within the range your charge controller can take in. For example, the max voltage (Voc) of my solar panel is 21.7V, max current (Isc) is 2.65A (see the sticker on the back of the panel for these specs), and my charge controller can take a max of 30V, 6.5A, so I'm well within the bounds.
• a solar charge controller for a 12VDC system -- choose one that can source at least twice as much current as what your keyboard will draw. For example, my keyboard draws a max 1.5A (from the power adapter). I'm using a Morningstar SunSaver-10-12V, which can source 10A. Overkill, yes, but I feel safer. There are other, cheaper charge controllers for 12VDC, but I haven't tried them - let me know if you do!
• a 12V sealed lead-acid battery -- I'm using a UDP-12120, which can source 1.8A of current if need be, so it could power the keyboard at max volume with all the keys pressed down at once, if there were no solar. I use lead-acid because most solar charge controllers are designed for the reliable workhorse lead-acid batteries, so I didn't have to do any other special circuitry. Note: a charge controller for lead-acid batteries will NOT work for lithium-ion or other battery chemistries!

In selecting the parts, choose a 12V battery that could supply slightly more than the current you need for however long you need it, in case it's a cloudy day. In my case, my keyboard uses a max current of 1.5A, and let's say I want to run it for three hours. Then I want a battery that can source at minimum 1.8A, and has a capacity of at least 1.5A*3hours = 4.5Ah. I've found that the batteries I've bought don't seem to be able to source their full rated amount, so to be safe, multiply that by a factor of 2. I am using a 12Ah battery, so overkill, but for maybe $10 extra, I can be more sure the system will run as long as it needs to run.

Total cost of the supplies:

• keyboard: $100-250
• solar panel: $75-200
• solar charge controller: $10-60
• lead-acid battery: $20-$40

The additional tools and supplies you'll need are:

• wire strippers
• electrical tape
• phillips screwdriver (for the charge controller connectors)
• 14AWG outdoor rated wire, in red and black (optional in the sense you could use indoor-rated wire down to 22-24AWG for current < 3A. Outdoor-rated wire can withstand exposure to UV and humidity better than indoor-rated wire can, but if you're ok with swapping out your cabling every once in a while, then indoor-rated wire should be fine)
• six alligator clip jumper wires, in yellow and black, or red and black (optional)
• zip ties (optional, for strain relief)

Step 1: Cutting and Stripping the Keyboard AC Adapter Cable

Alright, let's cut some cables and void some warranties!

Safety note: MAKE SURE YOUR POWER CABLE IS NOT PLUGGED INTO THE WALL during this step! Let's not electrocute ourselves at step 1!

The power cable that came with your keyboard should have two ends - one that goes into the wall, and one that goes into your keyboard. We're going to snip the wire on the side that goes into the keyboard. I want a long cable so I can reach from the keyboard to the ground, but I also want to be able to reconnect the cable to the adapter box so I can still play the keyboard off wall power later, so I cut it about six inches from the adapter box.

After cutting, you should see two wires inside the cable. Using the wire strippers, very carefully strip out the outer cable casing so that the two inner wires are sticking out by about an inch. You don't want to cut too far into the wire, or you'll end up cutting some of the wire itself!

With the two wires exposed, again use the wire strippers to very carefully strip about half a centimeter of insulation off each of the smaller wires. Be careful to not cut the metal inside! It'll still work if you nick one or two of the strands, but if you accidentally cut off more than a third of the metal strands, I advise you go back and strip more insulation off. More strands = more current-carrying capacity. Too few strands, and the wire might heat up from trying to carry more current than it is rated for!

I stripped both cut sides, because when I'm not using the piano outside, I want to be able to reconnect the two sides and power it off a wall outlet.

Step 2: Wire Up Your Solar Panel (or Hack Your Existing Solar Panel Cables)

Now let's wire up the solar panel! It's best to do this indoors, with the panel facing down, so it won't be producing any energy. NOTE: the front glass of a solar panel is pretty sturdy - it's designed to withstand hail! But the back teflon covering is pretty fragile, so try not to scratch it or drop anything on your panel while it's flipped over!

On the back of your panel should be a black junction box, or jbox. Mine didn't come with wires attached, so I had to add my own. IF YOUR PANEL CAMES WITH WIRES ALREADY ATTACHED, skip down to the second-to-last paragraph of this step.

Inside the junction box should be some screw terminals and blocking diodes. Mine was also labelled with which terminal was positive (+) and which was negative (-). I cut decently long lengths of the red and black 14AWG outdoor-rated cable, stripped the ends, and curled them into the positive and negative screw terminals, respectively. I stripped off about 3/4" of wire insulation so I could curl the wires around the screws, providing both mechanical support and extra electrical surface area contact.

Then, because inevitably someone will trip or pull on the cables, I added a few zipties to help support the wires, so they don't pull out on accident.

On the other end of the wires, I stripped off enough insulation to attach alligator clip jumper cables to each one: red or yellow for the positive (+) wire, and black for the negative (-) wire. Color-coding things now makes it easier to connect things later!

FOR THE PEOPLE WHO HAVE PANELS WITH WIRES ALREADY ATTACHED: First, make sure you don't plan to use this panel in an official setting again - with the cables hacked, they wouldn't pass electrical inspection. If that is ok with you, then go ahead and snip off the end connectors on your wires, and strip the ends so enough of it is exposed that you can clip onto it with the alligator clip jumper wires. Check which is positive (+) and negative (-), then clip on the corresponding alligator clips!

For a sanity check, now let's check that the panel actually produces power! We could have checked this at any point in this step, but let's be sure to do it now. Take your panel outside to somewhere sunny, hook up your multimeter leads to the corresponding alligator clips, and you should get something close to your Voc value. If it's a little less than Voc, are there clouds, or is the panel dusty? Otherwise, check all your connections and make sure they are tight.

Step 3: Connect Alligator Clips, Test Battery Voltage

I like to do all the wire stripping and taping indoors, so let's finish some last prep work before heading outside!

For ease of assembly and disassembly, I use alligator clip jumper wires on all my cables going between the solar charge controller to the solar panel, battery, and keyboard. Since the charge controller I'm using has screw terminals, I could just screw the wires directly in, and save myself some time. I prefer the alligator clips for the ease of use and not having to deal with exposed stranded wire outside under the sun.

First, check the battery voltage with your multimeter -- it should be between 11.5V and 14V. If it's low, you probably want to spend some time charging up your battery before you start playing piano.

Connecting alligator clips to the battery terminals is straightforward -- just clip them on horizontally! Use electrical tape to cover both terminals, in case anyone drops something metal onto the battery. I like to keep the battery in the cardboard box it came in, so I can additionally use the box to keep things from shorting or dinging the battery.

Double-check the battery voltage through the jumper cables, and make sure it's the same as before.

For the piano power cable, after connecting each alligator clip, wrap the end with electrical tape to (1) keep the exposed metal from accidentally shorting positive (+) to ground/negative (-), and (2) provide some mechanical support, so it will stick together.

The mechanical support is especially important for the thin power cable for the keyboard - use electrical tape to give it some support!

Step 4: Setup Keyboard, Connect Charge Controller!

Almost there, one more step to go!

Find a nice sunny spot for your keyboard stand. I set mine facing the sun, so the solar panel could lean against it and get some nice sunlight. I put the battery and solar charge controller behind the solar panel, so these indoor items won't be exposed to the UV and heat (though they still will be exposed to humidity, so watch out for that).

Follow the instructions in the user manual for your charge controller on which order to hook up the parts; stay safe! For mine, the instructions were to hook up in this order:

1. load - power (+) and ground (-)
2. battery - power (+) and ground (-)
3. solar panel - positive (+) and negative (-)

After connecting the battery, the red light on the Morningstar charge controller turned on. After connecting the solar panel, the green light on the Morningstar charge controller turned on. It was a good safety check. All was well!

Technically, you might have to ground your system to the earth... but as this is all relatively low-voltage, I hope it's ok that I skipped that. Any electricians out there, please please correct me if this is wrong!

Step 5: Turn on Keyboard and Jam!

If your charge controller is blinking green (or the color that means all is connected correctly), then ... it's time to turn on the keyboard!

Go ahead, turn it on. Does it turn on?

You're ready to jam!! Enjoy!!

Send me photos if you do it! Also send me ideas for where I should perform! Or if you want to perform, let me know too -- if it's within an hour driving distance, I can try to bring it to you!