PNP and NPN sensors are actually using the saturation and cutoff of the triode, and output two states, which are switch sensors. But the output signal is diametrically opposed, high and low. The PNP output is low level 0, and the NPN output is high level 1.

PNP and NPN sensors (switch type) are divided into six categories:

1. NPN-NO (normally open type) 2, NPN-NC (normally closed type) 3, NPN-NC+NO (normally open, normally closed common type) 4. PNP-NO (normally open type) 5, PNP- NC (normally closed type) 6, PNP-NC+NO (normally open, normally closed common type)

PNP and NPN sensors generally have three lead wires, namely the power line VCC, the 0V line, and the OUT signal output line. 1. NPN class NPN means that when a signal is triggered, the signal output line OUT is connected to the power line VCC, which is equivalent to a power line that outputs a high level. For the NPN-NO type, when there is no signal trigger, the output line is floating, that is, the VCC power line and the OUT line are disconnected. When there is a signal trigger, the same voltage as the VCC power line is issued, that is, the OUT line is connected to the power line VCC, and the high level VCC is output. For the NPN-NC type, when there is no signal trigger, the same voltage as the VCC power line is issued, that is, the OUT line is connected to the power line VCC, and the high level VCC is output. When a signal is triggered, the output line is floating, that is, the VCC power line and the OUT line are disconnected. For the NPN-NC+NO type, in fact, there is one more output line OUT, which is selected according to needs.

2, PNP class PNP means that when there is a signal trigger, the signal output line OUT and 0V line are connected, which is equivalent to output low level, 0V. For the PNP-NO type, when there is no signal trigger, the output line is floating, that is, the 0V line and the OUT line are disconnected. When there is a signal trigger, the same voltage as 0V is issued, that is, the OUT line is connected to the 0V line, and the output output is low level 0V. For the PNP-NC type, when there is no signal trigger, the same voltage as the 0V line is issued, that is, the OUT line is connected to the 0V line, and the low level is output 0V. When there is a signal trigger, the output line is floating, that is 0V line and PNP, NPN can be used for any plc when the output current is suitable.

In fact, no matter for the PNP or NPN output sensor, as long as the output current can get the requirements of the PLC, it can be used for any type of PLC machine. This is how the programmer can program. The following is an example of the FX-1S series PLC:

1. FX1S requires an active low level. When using an N-type output sensor, program detection can be set to a rising pulse trigger. When the sensor is in place, the corresponding command can be detected and implemented normally.

2. When the P type is selected, it is high when there is output. At this time, as long as the sensor output current can reach the 4MA required by the PLC machine, it is only necessary to change the program detection to the lower pulse trigger. When the sensor outputs a signal, Equivalent to 0V - 24V mutation, which is a falling pulse, at this time PLC can also detect and implement the corresponding instructions. In fact, when choosing a sensor, what should we consider is the input current of the PLC input terminal. (Siemens is generally around 2MA, while the Mitsubishi FX series is around 7MA. As long as the sensor pull current or sink current is suitable for the requirements, both P-type and N-type sensors can be used.

Mitsubishi FX is a common optical circuit on the internal circuit board, so you can only use the NPN type Siemens or Delta PLC's COM terminal is suspended, you can choose the common yang or the common yin connection method, that is, according to the type of selection, a total of The positive connection method can only use NPN, the common yin connection method can only use PNP, but the PLC input has multiple sets of COM end, and each group can have common yang and common yin to eat.

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