Security Alarms & Sensors

There are many alarm systems on the market from the cheaper DIY installations, to the full remote monitored alarm services. These all pretty much remain isolated systems though, with no connection to environmental control and home automation. Our thinking is that the security system, alarms and sensors need to be an integral part of any Home Control System (HCS).

Many of the sensors used can support multiple services and functions. Temperature sensors can be used for heating and cooling control as well as for fire detection. PIRs can be used to detect occupancy and as well as intruders.

PIR Sensors

PIR sensor
Passive Infra-Red (PIR) sensors detect the heat given out by the human body and can be used to detect intruders within rooms. In addition they can be used to detect occupancy of rooms and buildings and drive environmental conditions such as lighting and room temperature.

PIRs can be bought for use in different situations. Some have focussed sensitivity for corridors, some are designed to stop false activation by pets. 360° PIR sensors can be mounted in the ceiling and used to detect entry and occupancy from all directions.

We have completed a project to install PIR sensors in every room in our current house.

Magnetic Contact Sensors

Read more about why we have used door contact sensors in our current home.

Reed switches
Reed switches are simple switches that are activated by the presence of a magnetic field. Typically these are used in door or windows contacts.

door contacts
Reed switches are used inside magnetic door contacts and the plastic housing allows both parts to be recessed into a door and door frame.

window contacts
Reed switches are also used in window contacts and these are designed to be fixed to the frame surfaces.

Micro reed switches
Whilst the above are standard commercial items, it is much easier and cheaper to install your own micro reed relays, which can be bought very cheaply from places like eBay. These tiny sensors are easily hidden in door frames and once painted over are totally invisible.

Neodymium magnets
Similarly, you can buy Neodymium magnets cheaply. These are extremely powerful and very small (the ones pictured here are 6mm diameter and 3mm deep). This makes it very easy to hide them in doors and windows.

Tilt Switches

Tilt switch
A tilt switch uses mercury or a ball bearing to close internal contacts when it is tilted. Different designs have different angles of operation.

Pressure Sensors

stair mat
Stair mat sensors are used under carpets and have a pressure sensors to detect when they have been stepped on.

Beam-break Sensors

These sensors provide a beam of light between two points and detect if the beam is broken. The beam is usually infra-red and not visible to humans. Some systems use lasers to provide high accuracy and reliability over long distances. Beam break sensors are useful in situations where there is no physical deterrent or other means to detect entry by a person, such as a gate.

Shock / Glass-break Sensors

These are sensors that are fitted to windows and sometimes doors, to detect shocks or breakages.

Temperature Sensors

Although not commonly used in many homes today, many homes that have climate control or home automation use temperature sensors or thermostats in the rooms to enable control of heating or cooling systems. These can also be used to detect abnormal temperatures and provide an early indication of a fire.

One of the key challenges in installing temperature sensors in each room is in siting them and wiring them up. Wireless sensors are available but they tend to be quite large and obtrusive. Designing them into to a new build should be a requirement on any new home.

Smoke Detectors

Smoke detector
Most homes have smoke detectors installed. Many are battery powered but, the one pictured here is installed in our current house and is mains powered, with a battery backup. It is also in a series of linked alarms, which basically means that if one starts alarming, then they all do. This is particularly useful in large houses with many doors. Typically your will have linked alarms to cover different floors in a house.

Smoke alarms come in various types and you need to choose one suited to the location it going to installed in. Some are designed to work in kitchens and tend to be less sensitive.

We have completed a project to install networked smoke detectors in our current house.

The problem with have with most modern smoke alarms is that they lack style. They have been designed by engineers with function in mind. In reality, there is no real reason for smoke alarms to be unsightly bumps on the ceiling. They could be designed to be invisible or at least low profile or attractive to look at.

Manufacturers are slowly waking up to the idea of more attractive looking smoke alarms. This Kidde i9040 is nice and small and quite subtle.

Carbon Monoxide (CO) Detectors

We currently have several CO alarms in our house that are battery powered.

Wireless Sensors

All of the above sensors are wired into your home. Whilst this is quite easy to do when building a new home, it is extremely time consuming and difficult to retro-fit into an existing home. Fortunately, many of these sensors are also available in wireless form, using wireless technology such as Z-Wave.

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