ADDING PIR SENSORS TO CCTV
The new breed of CCTV cameras known as wireless internet CCTV cameras or IP cameras is totally digital, more like a computer than a traditional camera. This new type of camera detects changes in the digital image that its sensor “sees” to decide whether something has moved within the picture. This method of detecting movement can be improved upon by adding a passive infra-red (PIR) sensor to the camera, as this article explains.
There is a limitation to using internet CCTV cameras to detect movement. These cameras determine whether movement has occurred within their field of view by examining changes in the digital images that the camera’s optical sensor produces. One problem with this approach is that changes in the digital image may have been caused by something other than a person moving around. For example, if a streetlight suddenly comes on outside a room where the camera is located, there will be a big change in the digital image because it will be suddenly brighter. The camera will notice this change and will raise a motion detection alert – a false alarm in this case. There are several ways to resolve this problem, for example by using sophisticated image processing software in the camera or on a central computer so that people are “recognized” as people and an image-wide change in light level is ignored. A simpler solution, however, is to use a PIR sensor.
A top-quality wireless internet CCTV camera will usually have a small block of connectors known as an I/O or input/output port, which has several purposes. The port is just a series of holes where wires can be attached and tightened with a screw. The pair of connectors known as the input connectors are the ones used if you want to connect a sensor such as a PIR sensor. The inputs are used because the sensor is sending a signal into the camera, as opposed to the camera sending a signal outward.
You need to choose a PIR sensor that will work with the camera. The camera’s ports will be able to accept incoming signals of a certain wattage and voltage and attaching anything to the input ports that sends in electrical signals above the allowed range could damage the camera. Fortunately, most PIR sensors have a standard output signal, and cameras in Dallas/Fort Worth are designed to work with most of them. Choose a good quality sensor that can be adjusted for sensitivity and set to exclude the movement of small objects such as pets. To make fitting easier, go for one with a built-in battery. Although it is possible in theory to power the sensor from the camera, in practice it is tricky to get enough power to the sensor and often easier to go for the battery option. Next, we will look at how the sensor is attached to the camera.
Take a look at your camera’s manual to find the pair of input connectors within the connector block. Then, you simply take the two wires from the sensor and connect them to the input connectors of the camera, making sure you connect positive and negative wires to the appropriate connectors in accordance with the manual. It is no more difficult than wiring a plug. Next, attach the sensor to the wall or ceiling so it is “looking” at the same view as the camera. This means that when the sensor detects movement, the camera will be recording that movement. We also need to make a small change in the camera, as the next section explains.
The internet CCTV camera itself needs to be configured so that it will raise the alert and record images not when the camera itself detects movement, but rather when its input port receives a signal from the PIR sensor. It is usually a case of changing a single setting on the camera’s event set-up page, so that any motion detection “trigger” is ignored; rather it will be a signal from the input port that causes the camera to raise an alert. This is usually a simple change but will vary according to the camera model, so please consult the manual for details.
By using a standard PIR sensor with your wireless internet CCTV camera in this way, your camera will be able to detect movement more accurately and consequently the number of false alarms will be greatly reduced. Contact SDS Security, your PIR sensor expert in Dallas/Fort Worth, to learn more.