Using PIRs + Cameras Guide

Combining PIR motion detectors and surveillance cameras is a common way of improving how well cameras can 'see' in low light and alert against potential intruders. In the note below, we address the best ways to incorporate motion detectors with surveillance cameras, contrast the options, and discuss where best to use each type.

Why PIRs?

Matching video cameras with PIR sensors shores up a performance weakness found in many cameras: low light visibility. When relying on video motion detection, the sensitivity is tied to how well the camera 'sees' in low light. If a camera produces poor image quality in darkness, then the camera's motion detection will perform poorly as well.

One method of overcoming the difficulty is to add or pair the camera with a PIR - passive infrared - motion detector. As we have covered in previous posts, PIRs are frequently used in intrusion alarm systems to detect movement even in total darkness. Because the sensor detects heat contrasts, it is not dependant on visible light for operation. When used with cameras, the PIR can be used to 'manually' trigger recording in the camera and be used to turn on onboard illuminators or additional lights, thereby overcoming a 'weakness' in most cameras.

3 Major Options

The image below shows the major forms where the integration is commonly found:

Motion sensors are paired with cameras in three basic ways. In the section below, we compare these methods and discuss where each option is used to it's greatest advantage.

• Option 1: PIR sensor, with embedded Camera: This type of product can best be described as a normal alarm system type PIR Sensor with a camera hidden in the housing. As a result of the uncommon form factor, these units are often marketed as 'spy' or 'covert' units, because the untrained eye will assume the unit is just part of the alarm (non-video) system. However, these units are typically poor performing. The onboard cameras are commonly low resolution, black/white only, or 'still image' only units, and no popularly producted IP model exists. Many units in this category are designed to be stand alone camera with on-board storage only. When selecting these units as part of a general surveillance system, care should be taken to confirm video outputs exist and are compatible with DVR/NVR units.
• Option 2: Camera, with embedded PIR sensor: Devices in this class are security cameras first, but have the addition of an onboard PIR sensor added. This option in generally found in cube cameras, and often includes matching a white-light LED as a method of extending 'low light' coverage to less expensive, non Day/Night cameras. However, while the camera may be full-featured, the onboard PIR is limited to short, fixed ranges and has limited utility.
• Option 3: Cameras paired with External PIRs: This is most common option due to ability to select both camera and PIR according to the environment. This method relies on the PIR being wired to a camera's I/O port, but aside from that requirement any camera can be matched with any PIR. This flexibility allows long-range, weather proofed sensors to be matched with outdoor cameras - a combination not found in the other two options. More than one PIR can be wired together, greatly increasing coverage distance or blind spot avoidance of a single integrated sensor.

Cost Breakdown

The section below provides a few examples of each option that are commonly used with video surveillance.

PIR sensor, with embedded Camera

The units below are both equipped with BNC outputs for installation into analog surveillance systems. In both cases, the PIR is functional, but this is not always the case, especially with less expensive models.

• Interlogix (Kalatel/GE) PI-450: B/W, 425 TVL analog camera, 1 zone PIR range of 20 - 30 feet. Indoor only: ~$150 online
• Bosch CAM940C: Color, 420 TVL analog camera, 2 zone PIR range of 15 - 20 feet. Indoor only: ~$200 online

Camera, with embedded PIR sensor

The units below are atypical of most common PIR integrated cameras in that they are not the 'cube' form factor. Cube form factors are not ideal for many surveillance deployments, but the models listed below follow traditional units.

• Vivotek FD7131: Dome camera, 640x480, varifocal 3.3-12mm lens, onboard IR LEDs, 1 zone PIR range of 20 - 30 feet. Indoor only: ~$350 online
• Mobotix M12: Dual Color and B/W imagers, MP resolution, 22mm or 43mm options, 1 zone PIR range of 20 - 30 feet. Indoor/Outdoor rated: ~$1500 online

Cameras paired with External PIRs

The units listed below are typical of outdoor PIRs matched with surveillance cameras. Only the sensors are listed; no cameras or accessories like power supplies or mounting brackets are not listed. Given the variety of units available, the units listed below demonstrate only a small portion of potential ranges, coverage zones, and relay output.

• Optex SIP-100 Redwall: 12/24 ADC/AC powered, up to 3 configurable zones and 300' detection. Multiple relay outputs for cameras and other PIRs. Outdoor rated: ~$750 online
• Takex PA15WE: 24VDC/AC powered, single zone, 40' x 40' coverage area. Up to four relay outputs for cameras and other PIRs. Outdoor rated: ~$200 online