The advent of electronics technology & miniaturization has opened a whole new world of devices that can be truly personal. Yes, now you do not have to carry various electronic devices, you can wear them like your other accessories. These personal devices can be used to monitor our activity, provide us necessary information and exchange our data to main computer for further processing & storage. These wearable gadgets can be an extension of your other electronic products like Smartphone, Tablet or PC.
There are many situations where we would like to have routine information on a regular interval. For example, these kind of wearable device can be used to measure our fitness while doing exercise and also it can exchange these data with other devices like Pedometer & Heart rate monitors for further processing. Useful data like navigation & location information can be provided while doing outdoor activities like Biking, hiking trekking & sailing. Healthcare is also a very big field where these wearable devices can be very useful. Patients & aged persons can be continuously 24 * 7 days monitored for their wellbeing and we can have alerts whenever any critical event happens like fall or sudden change of other parameters.
Increased performance & integration of microcontrollers along with miniaturization has propelled design & development of these devices. At the heart of these portable & wearable devices are highly integrated microcontrollers that not only gather data ,process the information and exchange and display the processed data with other devices like PC, smartphone or Tablets for storage & further application.
Now let us see what points are important to design such wearable devices.
1. Maximum utilization of battery life.
This is the foremost concern of any design when portability is concerned. The designer has to balance the active part timing & asleep timing. Active part timing is when the components are actively processing the sensor inputs & communicating & updating other devices and display. This is done periodically and in between they sleep, drawing very minimal power from battery. This is the best way to conserve limited resource of battery power, there by maximizing the battery life. This also reduces the frequency of battery charging. Though the bigger battery can provide more power & more life, since wearable devices has to be portable & light, designer has to find a optimized balance between size & type of battery and current consumption during active & sleep mode.
2. Ultimate size of the wearable device –
Being portable automatically forces designers to make the product light & as small as possible. For example if any device is to be worn around neck or wrist, it has to be very light weight and of small form factor. This can only be done with the help of high integration of every part of electronics involved including battery. The lower the size & power of battery, higher the need to have very power efficient design.
3. Communication –
This again is the very important factor of designing wearable devices. The choice of communication protocols depend upon many factors like power consumption, throughput and the cost.
Bluetooth is the most preferred & used protocol. We have now Bluetooth Low Energy technology that uses very little power. As Bluetooth is available to almost all smartphones & tablets, it becomes logical to use this protocol.
WiFi is also another protocol which can be used for wearable devices. Though throughput of this protocol is high, its power consumption is also high.
There are also other protocols like Zigbee, WiFi Direct, 6LoWPAN for designers to implement.
The only hardware communication protocol implemented in such devices is USB. This is used for uploading the data to PC. USB connectors being very small, it becomes very easy to integrate them into any design.
4. Processing the Data –
Though the sensors are connected to microcontrollers permanently, it is the responsibility of microcontrollers to decide when & how to take data from sensors. This depends on the type of data that is required by the system. Fast changing parameters have to be monitored frequently while slow changing parameters like temperature can be monitored periodically taking a nap in between to conserve power. With the onslaught of ARM processors, designers have now 32 bit power very handy as 32 bit ARM microcontrollers with inbuilt peripherals and high computing power, are becoming cheaper day by day. These controllers provide high computational power which results in more local processing of sensor data and higher accuracy.
5. User interface –
Now a days, designer has very wide choice of devices from leading manufacturers like ATMEL, Microchip, ST, Freescale, Philips etc. All have come out with latest ARM controllers having inbuilt interface for LCD and operating at a very very low power.
Do not be surprised if these smartphones and tablets will vanish ! They will become part of our daily ware !