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Today, I will talk to you about how to judge whether the proximity switch used by PLC is PNP or NPN. Many people may not know much about it. In order to make you understand better, the editor summarized the following content for you. I hope you can get something according to this article.

Proximity switches are widely used in industrial control and automation industries. As the input device of PLC, the automatic detection of detected objects can be realized in order to realize linkage control. From the core devices, the proximity switch can be divided into PNP type and NPN type. The connection mode of these two forms of proximity switch is different from that of PLC. The type of proximity switch connected by PLC can be judged from the connection mode of proximity switch and the output signal. The following is a normally open proximity switch to explain how to judge its output form. The main results are as follows: (1) through the external resistance, it is judged that the core component of the proximity switch is the transistor, and its output is in the form of OC, and the access resistance is needed when accessing the PLC. The NPN type should be connected with the pull resistor, when there is no signal, the transistor is turned on and the output level is high; when there is a signal, the transistor is turned on and the output is low; the PNP type is connected to the pull-down resistance, when there is no signal, the Triode cutoff output low level; when there is a signal, the transistor turns on and outputs high level. Therefore, the type of proximity switch can be judged by the form of external pull-up resistor. If the pull-up resistance is connected, it is NPN type; if the pull-down resistance is connected, it is PNP type; as shown in the following figure.

2 judge by analog signal and output signal

The function of the Triode is to detect in place. If there is an obstacle approaching, the signal is output; otherwise there is no signal output. It is widely used in automatic assembly line and robot arm. Taking the normally open proximity switch as an example, this paper introduces how to judge the type of proximity switch. Use a detection object to simulate the signal. When the detection object is far away from the normally open proximity switch, the output signal is recorded, and then the detection object is placed close to the proximity switch, and then its output signal is recorded. The detection diagram is shown in the following figure.

The signal analysis is as follows: when there is no obstacle, the output level of the proximity switch is high; when there is an obstacle, the output level is low, then it is NPN normally open proximity switch; when there is no obstacle, the output level of the proximity switch is low; when there is an obstacle, the output high level is PNP normally open proximity switch.

Proximity switch is a commonly used position detection sensor, also known as contactless stroke switch, which is used to determine the non-contact position. It is an automatic detection sensor widely used in industry.

After reading the above, do you have any further understanding of how to determine whether PLC uses a proximity switch, PNP or NPN? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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