https://vedard.com/blog/photoelectric-infrared-beam-detector
Source: vedardalarm.com
Date: 2025/12/17
1. Infrared Beam Detector System Design:
An infrared beam detector, also known as a “photoelectric beam detector,” typically consists of a sight, beam intensity indicator, spherical lens, and LED indicator. Its detection principle utilizes infrared light emitted by an LED infrared light-emitting diode, which is then focused by an optical mirror to transmit the light over a long distance to a receiver. An alarm is triggered when the light is blocked. Infrared light is invisible and diffuses, forming a conical beam when projected. Infrared light emits 1000 beams per second continuously, making it a pulsed infrared beam. Therefore, these beam detectors cannot transmit over very long distances (within 600 meters). Detectors using beam-blocking technology interrupt the invisible infrared beam when someone crosses the monitored area, triggering an alarm. This is commonly used in outdoor perimeter alarm systems.
https://vedardalarm.com/quad-beams-wired-active-infrared-detector-outdoor-150m-p-67
2. Paired Use: One transmitter, one receiver. The transmitter emits one or more beams of infrared light invisible to the human eye, forming a warning line. When an object passes through, the light is blocked, the receiver signal changes, and after amplification and processing, an alarm is triggered. An appropriate response time must be selected for the infrared beam detector: too short a response time can easily cause unnecessary interference, such as birds flying by or small animals crossing; too long a response time can lead to missed alarms. The minimum blocking time is usually determined by a speed of 10 meters per second. If the width of a person is 20 centimeters, the minimum blocking time is 20 milliseconds. An alarm is triggered if the response time is greater than 20 milliseconds, and not if it is less than 20 milliseconds. Currently, common active infrared detectors include two-beam, three-beam, and four-beam models, with distances ranging from 30 meters to 250 meters. Some manufacturers also produce long-range multi-beam “light walls,” mainly used in factories, mines, and some special locations. 2. Infrared Beam System Principle: Active infrared beam intrusion detectors consist of an active infrared transmitter and an active infrared receiver.
3. Infrared Receiver Composition: An active infrared intrusion detector is a device that generates an alarm when the infrared beam between the transmitter and receiver is completely or partially blocked. Active infrared transmitters typically use infrared light-emitting diodes (LEDs) as the light source. Their main advantages are small size, light weight, long lifespan, and the ability to operate on both AC and DC power. They can also be directly driven by transistors and integrated circuits. Most modern active infrared intrusion detectors use a complementary self-excited multivibrator circuit as the driving power supply, directly applied across the infrared LED to emit a pulse-modulated infrared beam with a high duty cycle. This reduces power consumption and enhances the anti-interference capability of the active infrared intrusion detector. The photoelectric sensor in the active infrared receiver typically uses photodiodes, phototransistors, silicon photocells, silicon avalanche diodes, etc., according to GB/T 10408.42000 Intrusion Detectors Part 4: Active Infrared Beam Detectors.
4. Intrusion Detector Specifications: When the detector is operating at the detection distance specified by the manufacturer, if the duration of complete or percentage-blocked light transmission of the radiated signal exceeds 40ms, the detector should generate an alarm. Why provide a range? Because different usage locations can have different minimum blocking times set (adjusted), which helps reduce false alarms. The infrared beam divergence angle emitted by the active infrared beam transmitter is specified in GB10408.4 2000 standard: When used indoors, with the transmitter and receiver correctly installed and aligned, and operating at the detection distance specified by the manufacturer, the radiated energy is 75%. When persistently blocked, the receiver should not generate an alarm. To reduce false alarms, the transmitter and receiver axes should be aligned during installation and use. Infrared Beam System Product Features: 1. Resistance to strong light up to 50,000 LUX, built-in automatic adjustment. 2. Strong light filtering system to avoid interference from strong light or car headlights. 3. Unique optical design: The photoelectric beam can penetrate multiple layers of glass, possessing special environmental resistance. 4. Fully sealed integrated structure design to prevent rain, fog, dust, insects, etc., allowing it to operate normally in harsh environments. 5. Multi-level LED indicator for receiving signal strength, enabling more precise calibration. 6. Adjustable infrared beam interruption period, making it more flexible and adaptable. 7. Perimeter detection range: Determined by each model, maximum distance: 1100m. 8. Lightning-proof circuit design. 9. Advantages of infrared beams for perimeter defense: 1. Concealed defense method: Intruders are alerted without their knowledge. 2. Comprehensive perimeter defense: No blind spots or dead angles. 3. Complete defense capability: Intruders cannot pass through the coverage area of ??the invisible infrared defense beam net by jumping, crawling, or other actions. 4. Good anti-interference characteristics: When insects or small animals pass through the infrared defense beam net, no false alarm will occur because the infrared defense beam cannot be completely blocked. 5. Strong anti-vandalism capability: When the power line or signal line of the infrared receiver is cut, the alarm signal output circuit will automatically output a wireless alarm signal. 6. Can work in all weather conditions. The infrared beam detector has strong resistance to interference from adverse weather conditions. 5 System Application Overview The burglar alarm system solution mainly targets the economic losses and property security caused by perimeter intrusion. It also aims to improve the overall collaboration capabilities of the client’s security department and the comprehensive dispatch and response capabilities in the event of an intrusion. The entire solution uses multi-gate monitoring and simulated electronic map display of the alarm area. Regarding product selection, considering the defects in the installation and wiring methods of the first-phase burglar alarm system and the instability of the burglar alarm equipment, the products in this burglar alarm system solution, after market research and comparison, adopt a bus-based infrared beam system.
5. In response to the requirements of the Mianzhu City Quality and Technical Supervision Bureau, our company installed six pairs of infrared beam detectors on the perimeter wall of the Bureau’s office, inspection, and testing building area. These detectors will trigger an alarm if unauthorized personnel climb over the wall and enter the area. Based on the alarm zone information, the direction and location of the unauthorized entry will be quickly determined. 6. Product Introduction 1. FC-7448 Alarm Host The FC-7448 large alarm host system is highly versatile and widely used in residential perimeter alarm systems, building security systems, and various large-scale security systems in factories, schools, warehouses, etc. It can be computer-managed and easily integrated with other systems. It comes with 8 zones and can be expanded to 240 zones (excluding detector power cables) via a two-core bus, for a total of 248 zones. The total bus length reaches 2.0km (1.5mm). It can connect to 15 keypads, divided into 8 independent zones, each capable of independent arming/disarming. It has 200 personal operation keys, 30 programmable zone functions. Multiple zone expansion modules are available: 8-zone expansion module FC-7408, single-zone expansion module FC-7401, dual-zone expansion module FC-7402, six-zone keypad FC-6Zkey, single-zone expansion module FC-7401+ with output, and detectors with address codes. The auxiliary output bus interface can connect to peripheral devices such as FC-7448, FC-7412, and FC-32B relay output modules. It can realize various alarm/output relationships, including one-to-one, many-to-one, and one-to-many. Direct connection to a computer can be achieved via FC-7412, or connection to a LAN via the interface device. Connection to the alarm center can be made via PSTN, supporting multiple communication formats such as 4+2 and Contact ID. Keyboard programming or remote control programming is possible. Wireless expansion function is supported.
Infrared beam ABU-150 wired and bus compatible, digital eight-segment frequency conversion, on-site holographic real-time reporting. Unique displacement reception, high-power digital filtering. Full-function diagnostics, environmental adaptation, fault locking. Digital fuzzy artificial intelligence recognition: Adopts artificial intelligence fuzzy judgment, minimizing false alarm rate. Intelligent power transmission: The self-developed chip can automatically sense changes in the surrounding environment and automatically adjust the transmission power of the beam according to the environmental conditions, greatly extending the life of the transmitting tube.
Extended service life and reduced energy consumption. Green and environmentally friendly: Features a controllable display that can be turned off after installation and debugging, significantly saving energy. Patented coaxial aspherical dual-focal-length precision optical focusing lens. Dedicated DSP chip, patented multi-dimensional fault tolerance, true detection alarm technology. Employs long-life, contactless, low-voltage, low-power solid-state relays. Simultaneous adjustment structure for upper and lower optical lenses, making adjustment faster and more accurate. Adjustable beam axis without opening the casing. Model: ABU-150 Outdoor detection distance: 150m (outdoor), 450m (indoor) Number of beams: 3 Light source: Infrared digital pulse sensing speed: 50-700ms Alarm output: Normally closed and normally open (NC & NO) Contact capacity: AV/DC 30V/0.5A Alarm output: Bus MA Bus: Constant current carrier type Working voltage: DC 13.8V-24V; AC 1
The second phase of the perimeter wall uses a recessed installation method for the pre-embedded conduit. An 86-type junction box is installed every 20 meters. Four-core 1-square-millimeter cables are used for the infrared receivers and transmitters at the inner corners of the wall. The conduit is pre-embedded and uses standard wiring and power lines for connection.