(Continued from Part 2.)
There’s another potential option for alerting that could be categorized as ‘mobile centralized’ – it’s possible to set up a radio transmitter connected to a centralized console that would transmit a pre-recorded voice alert (e.g. ‘Alert in zone 3 North’) to a radio that you carry around with you. Some of the sensors I’ll be discussing later have this capability built-in, but you could implement a similar function using a Raspberry PI computer to monitor the sensors, connected to a RTL-SDR software-defined radio to transmit pre-recorded audio alerts. Implementing this would be moderately complicated and is beyond the scope of this article, but I’ve started experimenting with it and I may submit another article with more details in the future. (Remember that ‘never-ending project’ my wife complains about?)
Wired vs. Wireless Remote Sensors
When planning and selecting electronic remote sensors that trigger an alert back at a central console, you’ll need to consider how to get the signal from the sensor location to the console. There are two approaches you can take – wired or wireless. Wired tends to be more reliable, especially when dealing with long distances, but it does require that you purchase, run and connect the wiring, which typically means digging trenches and burying it for outside sensors or running it through walls for interior sensors. Longer wires can also impact the behavior of the system, since the electrical resistance will increase as the wire length increases and can vary with temperature, and longer wires can also act like antennas and potentially pick up interference from other electrical sources. Wired sensors tend to be simpler to design and implement, since the sensor can act like a simple switch that’s either ‘on’ or ‘off’ – you don’t need to worry about powering a remote sensor.Continue reading“Elements of a Security System – Part 3, by J.M.”