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Household Sensors

Sensors automate our lives

With increasing automation in our lives we are surrounded by sensors to make our lives easier or safer. They switch things on, switch things off or make adjustments so our lives become more predicatable and give us fewer things to think about in an ever more complicated world. They can even save our lives. Here we look at some of the many sensors in our lives and what they are used for.

We are surrounded by sensors

Sensors are very common these days and in fact we unknowingly are surrounded by them. They make our lives easier by providing control (or chaos if they go wrong) and in many ways they manage our lives.

They operate day in day out waiting for information and ready at a moment's notice to make a decision and adjust something for us.

Sensors and Feedback Systems

A sensor is the main component in an equipment feedback system. A machine or piece of equipment uses a sensor of some kind to measure or take note of something and feeds the information back to the machine to switch itself on, switch itself off or adjust something.

One of the early forms of sensor is the trusty ball valve used for over a hundred years in toilet cisterns and water tanks. The ball floats on the surface of water and "senses" when the water level falls, it opens a tap allowing water to flow into the tank until the water level is restored.

Most of us use water pumps to pump water from a bore and to pump water through our household plumbing systems. Household water pumps usually have 2 pressure sensors. A low pressure sensor which switches the pump on and a high pressure sensor that switches the pump off. The majority of problems we have with our water pumps are caused by faults in these pressure sensors.

We are all familiar with air conditioners and refrigerators and their temperature sensors which, once again, switch the machine on or off depending on the temperature the sensor reads.

Sensors keep us safe.

Water heaters have thermostats to measure the water temperature and switch off the electric heating element. If the water gets too hot and starts to boil we may be in serious trouble.

Many gas appliances have heat sensors that sit in the gas flame to detect if the flame goes out. If the sensor goes cold it will know the flame has gone out and switch off the gas supply.

Our electrical circuits have contact breakers that detect if the flow of electricity is more than it should be. A high flow of electricity suggests a fault in an electrical circuit such as a short circuit that can cause fire. A high flow of electricity causes the circuit breaker to switch off the power supply. Before we had modern circuit breakers we had fuses to cut the power off . These worked by melting a thin piece of wire if they got too hot. By the way, believe it or not, some old houses still have fuses, if your house has fuses it is a good idea to replace them with circuit breakers particularly bearing in mind that many fuses were "fixed" with such sensible things as silver foil or bits of wire.

Designers of these various sensing devices tend to make sure that if the sensor itself fails it will fail in the safe position. You will find that if your thermostat fails in your water heater the heater will not switch on. Similarly if the gas heat sensor fails you will not get the gas to flow.

In more recent times we have smoke alarms to detect fire and sprinkler systems that automatically turn on the water if they detect heat.

Sensors make life easier by controlling equipment

Obviously sensors of various kinds play an increasingly important role in our lives, By combining sensors with clever electronic systems and mini computers they are becoming increasingly programmable. A whole science has been built up and is known as "control engineering" that is applied to many applications in our modern world such as controlling automated production lines, traffic systems and war machinery such as guided missile systems and robotic attack aircraft. BP are in the poo at the moment but how would they have got on without the availability of remotely controlled submersibles.

At a more local level air conditioners manage our air conditioners by measuring temperature and switching themselves on and off. We are all familiar with televisions that are able to tune themselves automatically. I have a satellite television system that picks up free to air television stations from around the world. It has a satellite dish that can move from one satellite to another to pick up a large number of programmes.

Sensors are used to accurately determine the position of the satellite dish, to measure the signal strength and to receive any instructions I may give it by using my remote control and selecting any particular programme.

Copyright © Phil Wilson August 2010
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