Exterior lights connected to a passive infra-red detector illuminate only when the sensor picks up the body heat of someone within range. The detector is also fitted with a photocell, so the lights operate only at night.
A passive infra-red system has two advantages over simple dusk-to-dawn lighting. A porch light, for example, switches on only as you or visitors approach the entrance, then switches off again after a set period. This means you’re not wasting electricity by burning a lamp continuously all night. Secondly, remote passive infra-red detectors can be positioned to detect an intruder almost anywhere around your home and will switch on all your security lights or only those you think necessary. The effect is likely to startle intruders and deter them from approaching any further.
Light fittings and sensors
Because infra-red detectors are designed to be mounted about 2.5m (8ft) above ground level, light fittings made with integral detectors tend to be for porch lighting and most of them are styled accordingly. However, since the lighting needs to operated for more than a few minutes at a time, remote infra-red detectors are often used to control powerful halogen floodlights. Floodlights are also available with built-in detectors, which simplifies the wiring.
Unless you position detectors carefully, your security lighting will be activated unnecessarily. This can be a nuisance to neighbours and, as with any security device that’s constantly giving false alarms, you will soon begin to mistrust it and ignore its warnings. Infra-red detectors have sensitivity controls so that they won’t be activated by moving foliage or the presence of small animals. However, if your house is close to a footpath, you will need to adjust the angle of the detectors so that the lights don’t switch on every time a pedestrian passes by. When fitting a remote detector, make sure it isn’t aimed directly at a floodlight that it is controlling – or its photocell will try to switch it off as soon as it comes on and the likely result will be a light that simply flickers and never fully illuminates the scene. It is also important not to position an infra-red detector above a balanced flue from a boiler, or any other source of heat that could activate the sensor.
It is usually possible to wire infra-red security lighting in exactly the same way as dusk-to-dawn lighting. However, as some detectors are capable of controlling several powerful floodlights, you may not be able to run them from the domestic lighting circuit. In which case, you will need to run a 2.5mm2 two-core-and- earth spur from a power circuit and
control the lighting with a switched fused connection unit. Use a 3amp fuse in the connection unit for a combined rating of up to 690W; a 13amp fuse for anything greater.
Wiring a remote Sensor
Unless the manufacturer’s instruction suggest an alternative method, wire an individual light fitting with an integral infra-red detector in the same manner as a dusk-to-dawn fitting.
To wire a remote sensor controlling light fittings mounted elsewhere, take the incoming cable from the junction box or fused connection unit into the back of the fitting and connect its brown and blue conductors to the second cable of the same size from the Load’ terminals back through the wall and on to the first light fitting. Sleeve both are copper earth conductors and connect them to the earth terminal. Wire the first light fitting using the method described for a dusk-to-dawn fitting, then connect another cable to the same terminals and run it on to the second light fitting, and so on.
Once all the connections are made, you need to set the infra-red detector’s adjustment knobs or screws. One of them is for setting the photocell so that the system operates only during the hours of darkness. A second control dictates the period of time that the lights will remain on – three or four minutes should be sufficient.
If you live in the Sudbury, Suffolk area and are thinking about upgrading your security get in touch with Mr Fix Electrician today by calling 01787 852069. Thank you!