Build a “mobile minder” to monitor device use

The “Internet of Things” (IoT) is a grand idea – a vision of a world in which everyday appliances can talk to one another seamlessly, and be monitored and controlled remotely.

So far, we’ve yet to see a truly exciting application for the concept. However, the technologies involved are now so cheaply available, and so easy to set up, that it’s perfectly feasible to set up bespoke IoT-style systems in your own home.

In this feature we’ll explore this by demonstrating how to build a simple wireless system that parents can use to monitor the time their children spend using mobile devices.

The anatomy of an IoT system

Most IoT projects consist of one or more “nodes” connected to a network. A node ordinarily comprises a simple electronic controller, one or more sensors (bits of hardware that measure or detect something) and, sometimes, one or more actuators (bits of hardware that do something, either physically or electronically).

In use, the controller collects input from the sensors and passes the information to a central control system. It may also instruct its actuators to carry out work in response to messages received over the network, or in direct response to sensor input.

For example, a farmer might install a system in his greenhouse that employs nodes throughout. Each node could take input from soil, temperature and humidity sensors and use its built-in processing capabilities to take action, such as opening or closing vents, turning water valves or directing automated picking rigs as needed.

All of this could be achieved without direct human involvement, but the data could also be fed back to the central control computer so that the farm managers could monitor and control the system as a whole. See Four great Internet of Things projects, below, for some other examples of real-world IoT applications.

The mobile minder project

Most of us don’t have farms to manage, but IoT principles can easily be turned to domestic purposes. Our chosen project is monitoring the time your children spend on their mobile devices, whether that’s playing games or using Facebook. However, since most children use a wide range of devices across numerous platforms, installing monitoring software on every one isn’t feasible.

The Raspberry Pi gives us the flexibility to create any reporting system we want

If we take an IoT approach, we can instead keep a physical track of every device – from a Nintendo DS to an iPad – and record when it’s picked up, what device it is and when it’s put down again. We can achieve this by placing a node in each child’s bedroom and a sensor in each device. Many types of sensor are available that can be easily attached to a microcontroller; in this case, we’ll use a simple magnetic switch.

Attaching a small magnet to each of the devices you want to monitor means the switch will close whenever the device is placed next to it. When a child picks up the device to play with it, the switch opens, notifying the microcontroller – and the parents in question – that the device is no longer there.

It certainly isn’t a foolproof system – it could be tricked with a fridge magnet, for example – but it offers a simple way of making compliance with the rules easy for the parents to administer, and equally easy for children to comply with.

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