You want to build something wearable but you’re not sure how to power it? You’re in luck: today I’m going to help you pick the right battery for your wearable electronics project. First, it’s important to know how much power your circuit uses. For most circuits, just look up the maximum current draw for each component, and add them together. Then pick a battery that matches or exceeds your amperage needs. This 1.5v rechargeable AAA battery stores 750 milliamp-hours, which means it can theoretically output 750 milliamps for an hour, or half as much current for twice as long.
If you have three in a battery pack, it can give you three times the voltage, 4.5V, at the same 750milliamp-hours. My flora, GPS, and eight NeoPixels, on blue only, total up to 210 milliamps of current draw. So these three aaa packs can easily run the project for about three hours. In reality, your pixels are probably not on full brightness all the time, and will therefore draw less current than you calculated. This power supply overhead is a good thing and means you’re not going to overtax your battery.
You can also just measure the current draw of your circuit using a benchtop power supply or a multimeter. I usually prototype my projects using a plug-in power option, then switch to battery power later. It’s just one fewer thing to troubleshoot. We have a bunch of different flavors of alkaline battery holders to suit your different needs, from this waterproof two aa holder all the way up to four. Each battery adds another 1.5V to your total voltage. For most wearable projects, stick to 2 to 4 Alkaline or rechargeables for about 3 to 5 volts.
Alkaline packs are great– the batteries are easily replaceable and the hard plastic keeps everything safe. But if you’re more advanced, you might like these power-dense and lightweight lithium-ion polymer rechargeable cells. These batteries come in many shapes and sizes and require a special charger to fill them up. Some are small enough to wear on earrings or other jewelry. Lithium cells are more delicate than alkaline battery packs and for this reason, need more care and attention to prevent being damaged.
You should never bend, puncture, crush, or otherwise abuse these batteries. I often wrap them in gaffer’s tape when embedding projects, like here on the Neogeo watch and in the pocket of my winter coat. Lithium batteries can get hot during charging they should also be charged off of fabric or the body. For that reason, we have a separate charger board. Unplug the battery from the connector to recharge from any USB port. For gemma projects, a slim battery holder with a built-in power switch is handy.
Coin cells are fairly high capacity for the size, this pack can give you about 6V and 250mAh.However, it can’t provide tons of current for long periods of time, this pack can power gemma plus three or four neopixels for a couple of hours– pack spares in case the party runs long. Many of you ask how to power a large number of pixels on the go, like on a video jacket. Sure, you could wear a huge 6V lead-acid battery in your backpack, but these days there are some lighter-weight options available.
For easy charging, nothing beats a pack of Nickel-Metal-Hydride batteries. Three AA’swill power most projects, four AA’s will alleviate the voltage drop that occurs over long lengths of conductive textiles. Instead of some long runs of thread, consider soldering in thin wire-wrapping wire instead. Another way to deliver juice to your power-hungry wearable is through these USB battery packs. We sourced them for the Raspberry Pi, but this bigger one can deliver up to two amps, enough to charge your iPad, and has10,000 milli-amp hours of capacity.
Flora is designed to handle 2A through the protection diodes with ease so you can just plug in the pack into the USB port and it can drive up to 100 NeoPixel LEDs. We hope this helps you pick the perfect battery for your project! Check out the batteries, holders, and chargers in the Adafruit shop, Wearable Electronics with me, Becky Stern. So you want to wear your projects out in the weather, huh? Maybe you’re going camping in the woods, out to Burning Man.
Building interactive dance costumes. Today I’m gonna show you some ways to build rugged wearable electronics projects to stand up to the elements, using what I like to call the “three Cs.” The first C is Construction. The mere layout of your components can do a lot to strengthen your build. Provide strain relief to wires using glue, zip ties, or stitching. Select led strips and pixels with weatherproof silicone sheathing, and use silicone adhesive to seal everything up.
Position circuit boards in places on the body that don’t bend or twist a bunch, like the sides of shoes, a jacket lapel, or in the brim of a hat. The less physical agitation your circuit experiences, the better. If your circuit might experience dust or body humidity, you may want to use thin, flexible silicone-coated wire instead of conductive thread. Soldered connections are less likely to get gunked up than sewn ones. The next C is for Coatings. Sand and salt air can corrode your circuit board, and there are many ways to seal them off from the elements. Conformal coating, plastic-dip, castable plastics, and resins permanently coat your circuit to keep out moisture and buffer abrasions. Not all coatings are durable.
Some break down under UV exposure. Follow the safety instructions to protect your skin, eyes, and lungs. But if you need to get in there to repair anything, you might want to go with something more temporary. This brings us to the last “C”: Coverings. You can use large-gauge heat shrink tubing, tablecloth vinyl, and other planar plastics to wrap around your circuits, or 3D print flexible enclosure using NinjaFlex filament.Or just cover your circuit by keeping it in between the layers of fabric, and use Sugru to ruggedize the power switch or other parts that stick out. All diy wearables require some care and maintenance at some point, but we hope these tips will keep you up and blinking for as long as possible in rough conditions.