Wireless PIR motion sensors

Wireless motion sensors are now commonly available at a low cost, allowing them to be installed practically anywhere without any wiring from the alarm control panel. Some of them still require an external power supply, but many operate on batteries. The alarm system must contain a wireless receiver compatible with the wireless sensor.

In this section, we'll take a look at how we can use our Raspberry Pi-based security system with wireless receiver devices.

433-MHz wireless alarm systems

Wireless systems use an unlicensed radio frequency to communicate between the various components of an alarm system. In the UK, the two most popular frequencies used are 433 MHz and 868 MHz. While the more recent systems now use the 868-MHz frequency, 433 MHz is still in widespread use as it has a slightly longer range than an 868-MHz system. However, the 433-MHz band is also used by many other devices, which makes it congested, whereas 868 MHz is generally used only for alarm systems...