How does a proximity switch control a frequency converter?
YouTube：https://youtube.com/shorts/5TcanmHLBdU
A proximity switch can control a frequency converter in the following ways. Here is a detailed introduction:
### Control by Digital Signal
- **Direct Connection Control**: A proximity switch usually has two output states, namely normally open and normally closed. Connect the output signal of the proximity switch directly to the digital input terminal of the frequency converter. Set the function corresponding to this input terminal in the frequency converter parameters as start/stop or forward/reverse rotation, etc. When the proximity switch detects an object approaching or moving away, its output state changes, thus sending corresponding control signals to the frequency converter to achieve control over the start, stop or forward/reverse rotation of the frequency converter and the motor.
- **Transfer via Intermediate Relay**: When the output signal of the proximity switch cannot directly match the input terminal of the frequency converter or signal isolation is required, the transfer can be carried out through an intermediate relay. The proximity switch controls the coil of the intermediate relay, and then the normally open or normally closed contacts of the intermediate relay are connected to the digital input terminal of the frequency converter to achieve control over the frequency converter.
### Control by Analog Signal - **Control by Voltage Signal**: Some proximity switches can output analog voltage signals, and the output voltage will change with the change of the detection distance. Connect the analog voltage output terminal of the proximity switch to the analog input terminal of the frequency converter. Set the corresponding relationship between the analog input and the frequency setting in the frequency converter, for example, set it as a proportional relationship between voltage and frequency. When the proximity switch detects a change in the distance of the object, it will output different voltage values. The frequency converter will change its output frequency according to the received voltage signal, thereby controlling the rotational speed of the motor.
- **Control by Current Signal**: Similar to the control by voltage signal, some proximity switches can output analog current signals. Connect the output analog current signal to the analog input terminal of the frequency converter. Set the corresponding relationship between current and frequency in the frequency converter parameters. When the proximity switch detects a change in the detection situation and causes the output current to change, the frequency converter will adjust its output frequency accordingly to achieve control over the rotational speed of the motor.
### Communication Control - **Fieldbus Communication**: If both the proximity switch and the frequency converter support a certain fieldbus communication protocol, such as Profibus-DP, Modbus RTU, etc., they can be connected to the same bus network. Set the corresponding communication parameters in the frequency converter, such as station address, baud rate, data format, etc., to make it communicate with the proximity switch. The proximity switch will transmit the detected state or data to the frequency converter through the bus, and the frequency converter will perform corresponding control actions according to the received information.
- **Industrial Ethernet Communication**: In some automation systems, the proximity switch and the frequency converter can communicate through the industrial Ethernet, such as EtherNet/IP, Profinet, etc. This way can achieve high-speed and large-volume data transmission. The proximity switch can not only transmit simple switch states or analog signals but also transmit more complex detection data and instructions. The frequency converter will perform more precise control according to this information.
### Pulse Signal Control - **High-Speed Pulse Counting**: Some proximity switches can output pulse signals, and the pulse frequency is related to the moving speed or position change of the detected object. Connect the pulse output terminal of the proximity switch to the high-speed pulse input terminal of the frequency converter. Set the pulse counting function and corresponding control parameters in the frequency converter. The frequency converter will count and analyze the received pulse signals and control the rotational speed or position of the motor according to the preset logic.
- **Pulse Width Modulation**: Some proximity switches can output pulse width modulation (PWM) signals. Different detection results are represented by changing the pulse width. Connect the PWM signal of the proximity switch to the specific input terminal of the frequency converter. The frequency converter will decode and analyze the PWM signal and adjust the output frequency or other control parameters according to the change of the pulse width to achieve control over the motor.
