Photoelectric Detectors
The main consideration when installing any alarm system is to provide the ultimate protection for our families and business. Choosing the correct components for this are a major factor in any security system’s success
Photoelectric detectors monitor the movement of objects in a specific area. They are usually sold in pairs and consists of a separate transmitter and receiver. The transmitter produces an infrared beam which is picked up by the receiver. When the beam is broken, the detector triggers an alarm, activated a camera of whatever it’s been designed to do.
There are three main types of sensors – in the first ‘opposed arrangement’ system, the receiver is placed in the line of sight of the transmitter, When the beam is broken the alarm sounds.
The second is the ‘retroflective arrangement’. Here, the transmitter and receiver are placed in the same area, and a reflector bounces the signal between them. As before, any break in the beam and the alarm sounds.
The last option is ‘proximity sensing’. The main difference here is that the alarm sounds when the receiver sees the beam, rather than when it fails to. For example, it could be set to go off when a door is opened, there by completing the circuit.
The sensors come in a variety of shapes and sizes, from cylindrical ones that can be mounted on a pole, to rectangular ones more suitable for wall fixing. They use a combination of pulsed beams, perhaps 4 to a unit, and will only activate an alarm of all are broken. Others have upper and lower beams, giving you maximum protection throughout the area you are covering. This multiple beam technology makes sure that the beams aren’t influenced by rain, snow or fog. Most detectors come with view finders, so you can easily line up the beams, and have external LED indicators so you know they are working correctly.
When considering these detectors make sure of the coverage too, because they all have a limited range. Although this can be quite a substantial distance, buy the one that is right for you. It goes without saying that ones that cover larger distances are more expensive, and you don’t want to spend more money than necessary.
Some also come with an automatic gain control circuit. The purpose of this is to constantly monitor the overall strength of the signal, making allowances for the build up of dust, etc and then compensating accordingly. This stops many false alarms.
You might also want to prevent the alarm from sounding if a small animal breaks the beams. This can be accomplished on some models by having an adjustable beam interruption time. This means that if you set a large interval, an animal can run through the beam, but an intruder will set it off.
If you are going to mount them outside, it might be worth investing in ones that have adequate protection. They are usually mounted in a weather resistant casing, and can also be supplied with an internal heater if they will be operating in cold conditions. If not, you can buy accessories later.
Photoelectric detectors form the main component of any wireless security system, and hopefully you know have a greater understanding of the options available to you.