David Briddock reveals how building smart wearable tech can be cheap and fun
Smartwatches, fitness bands and other wearable products are all the rage at the moment. Yet there's a lot of fun to be had fabricating your own smart wearable, so it's not surprising to discover there's already a large community of makers, hackers, crafters, artists, designers and engineers doing just that -what sort of hardware platform is suitable for a wearable project?
Some have opted for the ever popular Raspberry Pi, but you'll need big pockets to house the Pi board, extra components, battery and associated wiring, while fashioning some sort of external attachment arrangement, such as strapping it to your arm, isn't exactly an elegant solution.
A more viable alternative is one of the range of miniature boards ideally suited to the DIY wearable enthusiast; boards that have more than enough computing power, useful built-in functionality, flexible connectivity options and battery-friendly power demands to perform a range of tasks. So let's take a look at a few of the most popular options and see how they compare.
Adafruit Flora
As you might expect from it's full name, the Adafruit Flora Wearable Electronic platform is an ideal starting point for a wearable construction journey. It's small dimensions - only 45mm in diameter - doesn't mean it's lacking in capability. It's built around the Arduino-compatible Atmega32u4 chip, the same one found in Adafruit's popular Atmega32u4 breakout board (adafruit.com/products/296).
With its on-board USB HIB support you can emulate a mouse, keyboard or MIDI controller and it's a straightforward matter to make a device-to-device connection. As for power, the schottky-diode-protected JST connection supports battery packs from 3.5 volts right up to 16 volts. Alkaline, rechargeable NiMh/NiCad, Lilon/LiPoly or LiFe Power batteries all work fine.
The clever design, which provides no less than 14 pierced contact pads for garment attachment and electrical connections, means it's easy to attach the Flora to a range of clothing and bags. All these connections are clearly labeled, with eight dedicated I/O pins to ensure a flexible range of input and output signal possibilities.
If you want to take out even more of the work, you can even buy a ready-to-go wearable kit (adafruit.com/products/1285) with sewable connective thread, various needles, sewable switches, candle-flicker LEDs, and CR2032 watch-type batteries with sewable battery holders.
Flora First Steps
As we mentioned earlier, Flora is designed to be beginner-friendly. Even connecting a battery the wrong way won't cause damage thanks to a polarised connector and protection diodes. And an on-board regulator means attaching a 9V battery won't end in tears either.
With it's built-in USB support there's no need for special cables or other programming hardware. You simply need to plug it in to your PC's USB port.
Flora projects can incorporate just about any type of sensor, for example colour identification, pressure, motion and even GPS tracking (learn.adafruit.com/flora-wearable-gps). To start your wearable journey try one of Adafruit's excellent hands-on tutorials (learn.adafruit.com). One will have your Flora blinking its onboard LED in no time, while another shows how to control a string of external LEDs. After that you can move on to the Smart Pixels tutorial (learn.adafruit.com/flora-rgb-smart-pixels).
Or how about a custom LED watch? One strategy is to incorporate a NeoPixel Ring, with 16 ultra bright NeoPixels LEDs, which can be programmed to indicate the current time. A leather strap can host the circuit and hide the battery. To discover more visit learn.adafruit.com/flora-geo-watch.
Adafruit Gemma
Conceptually the Gemma board is a bite-sized version of Flora. The tiny wearable platform is only 28mm in diameter and just 7mm thin, so it's perfectly suited to super-discreet wearable projects.
Powered by a 8MHz ATtiny85 processor it has 8K of flash, 512 bytes of SRAM, 512 bytes of EEPROM, five input/output pins, built-in data-logging and a choice of internal or external active antennas. Yet it needs only 9mA of current to run.
The latest Gemma (version 2) has a micro-B USB connector, plus a green LED to confirm a connected power supply and a red LED for input/output traffic pin one. And there's even a minute reset button for entering the boot-loader or restarting the program.
The smaller design means only three of the petals/pads are assigned to input/output duties, as opposed to Flora's eight, but once again they're clearly labeled and just as easy to use.
There's standard I2C compliant capability and you can program Gemma using the Arduino IDE. However, be aware that Gemma isn't quite 100% Arduino-compatible.
LilyPad Boards
Despite its impressive range, Adafruit doesn't have the monopoly on flower-like wearable technology. One alternative is the LilyPad range, based on a wearable e-textile technology developed by Dr Leah Buechley with support from SparkFun (sparkfun.com). In fact, SparkFun donates a small portion of each LilyPad sale to Dr Leah Buechley's work to support the platform development and e-textile education initiatives, while also ensuring the Arduino LLC can fund maker-oriented coding tools.
On-board a LilyPad there's an 8-bit ATmega328 microprocessor with 32KB ISP flash memory, 23 general purpose input/output lines, programmable serial communication and a six-channel 10-bit analogue/digital converter. It operates off an 1.8 to 5.5 volt supply and is controllable through Arduino software (arduino.cc), thanks to its Arduino bootloader.
Large connecting petals/pads encourage creativity and also help with garment installation. Plus there's a family of input, output, power and sensor boards. SparkFun even suggest a LilyPad is washable.