All you need to know before building a wireless sensor network

28th March 2017
Posted By : Alice Matthews
All you need to know before building a wireless sensor network

Sensors are, in many ways, the backbone of the Internet of Things. Since most IoT devices rely on the constant monitoring and collection of data - temperature, ambient light, humidity - and the detection of specific events in order to function, setting up the sensor network appropriately is key. After all, without the ability to detect that the temperature has risen to 30°C (87°F) with 80% humidity, the internet-controlled thermostat will not know to turn on the air conditioner so it’s a cool 21°C (70°F) when the homeowner arrives home.

Author: Jackie Roberson, Seek Visibility

Most consumer IoT devices are already equipped with the necessary sensors, and instructions on how to deploy them. If you want to build your own sensor network, though, there are some important things you should know to ensure that it works as expected and provides the information that you need.

Limit power usage
Embedded technologies generally offer different power modes; for instance, your sensors may switch into low-power mode during periods when they aren’t actively collecting data. Failing to properly configure your sensors can lead to excess power usage, and battery drain - and a gap in your data.

Therefore, to conserve power, consider using an MPLAB compiler to optimise your requests for data. By programming the compiler queries to track your desired variables at predetermined intervals, you’ll save power as the sensor devices switch into a lower power mode when not collecting data. As a bonus, if you program your sensors to only record data when something changes, or a new trend emerges, rather than constantly, you’ll both save power and limit the deluge of data.

It’s also useful to consider alternative power sources to keep your network functioning. Solar power and energy harvesting can supplement battery power - or in some cases, even replace it.

Start small, and scale up
Whether you are building your network for home or for business, it’s best to start small, and then scale up as you determine your needs. It may be tempting to build a large-scale network right out of the gate, but it’s better to begin small, target your measurements, and then adjust as you learn more and discover which data is most valuable. Otherwise, you risk wasting valuable time and money on an excessively complicated network.

Optimise your network for best performance
The physical environment of the sensors can make a significant difference in signal strength and the value of the data you collect. To ensure that you have the strongest, most reliable signals between your sensors and the gateway:

  • Position the gateway in the centre of the building, not along outside walls, to ensure equal signal strength throughout. Keep the gateway off the floor and away from walls or metal objects to avoid signal interference.
  • Limit interference. Wireless devices that operate on a 900MHz frequency can create noise on your wireless sensor network that affects data quality. To avoid interference, use devices that operate on a 2.4 or 5.8GHz frequency instead.
  • Install a signal repeater. If there is a significant distance between the wireless sensor and the gateway, use a repeater or extender halfway between them to strengthen the signal.
  • Consider the environment. Sensors that are exposed to the elements - water or high or low temperatures - should be enclosed in appropriate containers to avoid damage and ensure proper function.

Don’t forget backup
As you collect data for analysis, it will likely be stored on a server or computer. But what happens if communication is interrupted? You don’t want to lose the data, so implement a secondary storage system, such as an external SD card, to ensure that your data is safe.

Test and monitor
Not only do sensors need to be calibrated on a regular basis, but it’s also important to test and monitor your wireless sensors to determine how much bandwidth they are using on your network, and whether you are achieving the expected results. This is important, so as to avoid overwhelming the network or creating excessive cost increases.

Creating and deploying a wireless sensor network is not necessarily complex, but there are a number of details to consider. By carefully managing the power usage, size, bandwidth, and optimisation of the network, your investment will be worthwhile and produce useful results.

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