 |
About Us |
 |
|
|
|
|
| Home > About Us >Industry News |
| |
| System principle of wired alarm |
| 2021.01.28 |
|
The equipment of the anti-theft alarm system is generally divided into: front-end detector, alarm controller. The alarm controller is a host (like the host of a computer), which is used to control the processing of wired/wireless signals, detection of system failures, power supply, signal input, signal output, built-in dialer, etc. The alarm controller is indispensable in an anti-theft alarm system. Front-end detectors include: door magnetic switch, glass break detector, infrared detector and infrared/microwave dual discriminator, emergency button.
.png)
Security is mainly divided into three parts: monitoring, alarm, and access control. Chat with everyone to the police today. Our common security alarm systems are mainly divided into two types: wired and wireless. The wireless alarm system is very popular among home users because it is easy to install, has no cable constraints, and does not destroy the overall environmental style of the home. This is the main reason why small apartment and apartment-style smart home security products are mainly wireless alarms.
But in engineering projects, large villas, courtyards, commercial environments, or called systems engineering, the disadvantage of wireless appears. Therefore, wired anti-theft alarms are trusted by most intelligent integrators because they are stable and affordable. However, it seems that connecting wired detectors and anti-theft alarm hosts is a bit difficult for non-professional personnel. This reminds me of the first time I used the alarm panel (DS7400XI). It was the manual, the resistance, and the relay.
We know that the main components of a typical anti-theft alarm system are composed of three parts: the alarm main board, the front-end detector and the alarm sending device (networked alarm communication and on-site sound and light alarm).
The front-end detector also includes passive infrared, infrared plus microwave dual-check, infrared radio, infrared guardrail, manual alarm, fire house detection, glass breakage, etc., which are suitable for different environments according to different functions.
The front-end detector is the sensor of the alarm system, and the detection of the external alarm by the alarm system is completed by the front-end detector. As for the connection and signal transmission between the front-end detector and the alarm host, in the final analysis, it is a process of transmitting and receiving a switch signal. The so-called switch signal is the open and short-circuit process of an electrical circuit.
For example, the conventional alarm system generally adopts the normally closed working mode. When the system is powered on and works normally, if the detector loses power or is triggered by an alarm, the relay in the detector will act to change the contact from the closed state to the open state When the alarm host detects this change of the corresponding defense zone port, it will take corresponding responses (including ignore, alarm, signal output, etc.) according to the current status settings.
In fact, the working principle of the alarm host and alarm detector is very simple, but why in practice many people cannot configure and use it correctly? In fact, some key basic knowledge is not understood. Today I will talk to you about the connection between wired defense zones and wired detectors and alarm systems.
The basic knowledge is not less: what is the end of the line resistance.
End of line resistance (or end of line resistance) English EOL Resistor: End of Line (EOL, End of Line) circuit, the circuit characteristic is that the circuit terminal is connected to the resistance, the circuit short circuit to the ground will trigger the circuit contact action, such as when the system is armed, Any circuit break or short circuit will trigger an alarm. The scientific name is end-of-line resistance. The specific specifications of end-of-line resistance are different. Alarm panels of different brands and models have their own specifications. The resistance values of each manufacturer are different. Commonly used ones are 1KΩ, 2.2KΩ, 4.7KΩ, 5.6KΩ, 6.8KΩ, and On various detectors, which is the end of the line.
Use normally closed in series in the circuit and normally open in parallel in the circuit. When an alarm occurs, the host will detect the change in resistance. In other words, as long as the resistance of the detector output to the host is not the nominal resistance (Such as 4.7KΩ), it will alarm. The task is to prevent vandalism, you will also alarm if you cut the line or short-circuit.
It is clear that there are two ways of end-of-line resistance: one in series and one in parallel.
Normally closed circuit (NC): The short circuit is normal, and the open circuit alarms. The disadvantage of this circuit is that if someone short-circuits the circuit, the probe will lose its function. The alarm panel cannot recognize that it is an artificial short circuit.
Normally open circuit (NO): Short circuit alarm, open circuit is normal. The disadvantage of this circuit is that if someone breaks the circuit (cuts the signal wire), the probe will lose its function. The alarm panel cannot identify the section of the road that is artificial.
End of line resistance EOL: The short circuit is normal, and the open circuit alarms. The advantage of this circuit formation is: if someone breaks the circuit (short circuit back to open circuit), the alarm host can alarm. Short circuit alarm, open circuit fault, resistance value (for example, 4.7KΩ) is normal. The advantage of this circuit form is that it reacts differently to short circuits and open circuits, especially suitable for smoke detectors and emergency buttons. If a rat bites the segment or breaks due to help, the alarm host thinks that the circuit is faulty.
Therefore, in actual applications, simply connecting the normally closed and normally open loops instead of the detection of the end-of-line resistance, there is a great alarm safety hazard.
The meaning of alarm host AUX, Z-, Z+:
Unlike wireless detectors that use battery power supply, wired detectors usually use DC voltage to supply power, and the AUX of the alarm host provides power to the wired detectors at the power output of the detector. Usually the output voltage value of the alarm host AUX is DC12V, DC14V.
Z- indicates the negative pole of the wired defense zone, generally Z- is grounded (GND), and Z+ indicates the positive pole of the wired defense zone, usually with a certain voltage.
|
|
| |
|
|
