Analysis of various types and principles of PNP and NPN sensors

PNP and NPN sensors are actually switching sensors that use the saturation and cutoff of the triode and output two states. But the output signals are completely opposite, ie high and low. The PNP output is high level 1 and the NPN output is low level 0.

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

1. NPN-NO (normally open)

2. NPN-NC (normally closed)

3. NPN-NC + NO (normally open, normally closed)

4. PNP-NO (normally open)

5. PNP-NC (normally closed)

6, PNP-NC + NO (normally open, normally closed common type)

PNP and NPN sensors generally have three lead wires, namely the power line VCC, 0V line, and OUT signal output line.

1.PNP

PNP means that when a signal is triggered, the signal output line OUT is connected to the power supply line VCC, which is equivalent to a power supply line that outputs a high level.

For PNP-NO type, when no signal is triggered, the output line is floating, that is, the VCC power line and the OUT line are disconnected. When a signal is triggered, the same voltage as the VCC power line is issued, that is, the OUT line is connected to the power line VCC, and a high-level VCC is output.

For the PNP-NC type, when no signal is triggered, the same voltage as the VCC power line is issued, that is, the OUT line is connected to the power line VCC, and a 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 PNP-NC + NO type, in fact, there is an extra output line OUT, which is selected according to needs.

2, NPN type

NPN means that when a signal is triggered, the signal output line OUT is connected to the 0v line, which is equivalent to outputting a low level 0V.

For NPN-NO type, when no signal is triggered, the output line is floating, that is, the 0v line and the OUT line are disconnected. When a signal is triggered, the same voltage as 0V is issued, that is, the OUT line is connected to the 0V line, and the output outputs a low level OV.

For the NPN-NC type, when no signal is triggered, the same voltage as the 0V line is issued, that is, the OUT line is connected to the 0V line, and the low level 0V is output. When a signal is triggered, the output line is floating, that is, the 0V line and the OUT line are disconnected.

For NPN-NC + NO type, there is one more output line OUT and two output lines with inverted signals, which can be selected as needed.

We generally use the NPN type, which is an active-low state. PNP is rarely used.