A typical access control system contains at least four devices: access power supply, access control machine, electric lock, switch.The most common connection mode is to connect the electric lock, switch and access control machine to all access control power supply.Line one more, a lot of friends said very headache, too difficult.In fact, understand the principle behind the access control wiring is actually very simple.

　　Since the access control power supply is the central link of wiring, it starts from the access control power supply:

　　As soon as I saw so many terminals, I felt dizzy.Don't have to ah, apart, NO, NC, COM for a group, electrical lock, 12V, GND for a group, for the equipment power supply, PUSH1, PUSH2, for the switch signal line, the two switch signal line, the connection method is not the same, don't go to it, CONTROL, for the building linkage terminal.To simplify, the real use in most access control wiring is NO, NC, COM, 12V, GND, PUSH (PUSH1 above, referred to as PUSH).

　　The really hard to understand NC, NO, COM group, what the hell is this?Let's first understand from the English original meaning of NC and NO, NC is the abbreviation of Normal Close, Chinese translate to Normal Close, NO is the abbreviation of Normal Open, translate to Normal Open.This is actually the state of the contactor in the electrical field. In order to realize the opening and closing of the door in the access control system, a relay is used. The relay is a contactor.

　　It can be seen that contact 4 is on, and there should be a switch between D and E. When D and E switches are closed, contact B is disconnected and on with C under the action of electromagnet suction.It can be thought that under the action of NO external force (that is, D and E are not artificially closed), A is always closed, C is always open, A is the NC end, C is the NO end.Therefore, whether the power is on or off, A is always on (D and E are not closed artificially), so I think it is more appropriate to understand NC as contact closure and NO as contact disconnection.

　　Always hear the statement like this, NC is electric lock lock normally closed, NO lock is electricity normally open lock, on closer inspection is wrong, NO matter what the electric lock, in the case of internal conduction (electricity) should be open lock, only because NO lock is NO end, under the effect of NO switch signal, the internal contact and NO conduction, not conduct electricity, of course not locked,It's not like it's energized, but the lock isn't connected, but it's energized, right?

　　Extended to the principle of access control, when the lock is connected with the access control power supply, there are two lines on the general electric lock, one is connected with NC or NO, and the other is connected with GND to form a loop.If you want the lock to be closed normally, you can answer NC, otherwise, you can answer NO.There is also a PUSH interface on the access control power supply, which you must have thought of. Push and GND are the transfer switch, which is equivalent to D and E in Figure 2. When Push and GND are closed, NC and NO terminal contact will be converted to achieve the purpose of switch.This is called delay in the access control system. There is a delay knob on the access control power supply, and the time delay can be set within 60 seconds.Why is that? Well, you can think about it a little bit, but I'm not going to expand it.

　　Next an important issue, access control machine and access control power how to connect.If the core of the access control power supply is a relay, then the core of the access control machine is a relay.Not how to open the door, and credit card, password, fingerprint and face even open the door, they are all through the output switch signal to open the door, so, just think about a problem, since the core of access control machine is relay, it will output switch signals, so it either with NC, COM output, or with NO, COM to output, whether with which kind of,Because it is usually off, of course, to use NO, COM to output, so, NO matter what kind of access control machine, as long as it is through the relay control signal output, are the same connection.

　　12V, GND is for the power supply end, there is nothing to talk about, NC, NO, COM for the relay module, for the output switch signal, because the normal is disconnected, so it should be connected to NO, COM, and because it is used as a switch signal, so it is connected to the PUSH and GND on the access control power supply, forming a closed circuit.

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