How to connect the absolute encoder signal to a small PLC

①Canpen bus signal connection, some small PLCs provide Canopen interface, and the selection of Can interface is provided. The characteristic of Canopen signal is strong anti-interference, especially for anti-interference of frequency conversion. Multi-encoder bus type has fast connection speed and is suitable for more Axis multi-motor synchronous control.

②4-20mA signal, the 4--20mA signal output by the absolute encoder enters the PLC's own analog input. The characteristic of 4--20mA signal is that it is extremely practical and convenient. A multimeter can check the encoder and circuit during debugging and maintenance. The linear corresponding calculation of the input signal is also very convenient. The disadvantage is that the signal accuracy is lower than the digital signal, which is suitable for accuracy. It is not high, but it is used frequently, especially in occasions such as outdoors and on ships where users can maintain it themselves. At present, small PLCs have their own analog input interface.

③RS485 signal enters the communication interface of PLC (one communication port is required, if the PLC communication port is also connected to other equipment such as touch screen, it is necessary to select more than 2 communication ports when purchasing PLC). There are generally two RS485 interfaces of N80, the highest baud rate is 256KHz, and there is CRC check code to decode and check, which is rare in the RS485 interface of small PLC.

④Modbus RTU signal, PLC as the master station, and the encoder as the bus type connection of the slave station. Multiple (1-9) encoders can be connected. The PLC comes with modbus RTU protocol decoding instructions. The characteristic is that the protocol standard is reliable, the configuration is ready, but the data refresh is slow, an encoder generally takes up 50mS or more.

⑤The Easypro free protocol provided by the encoder manufacturer, PLC as the master station, and the encoder as the slave station, can be connected to multiple (1-9) Easypro encoders. PLC needs to configure communication program, baud rate, data bit format, etc. If the data is in ASCII code, you need to call the ASCII decoding command that comes with the PLC. This feature is simplified than modbusRTU, saving PLC resources, and each encoder takes about 30ms (19200 baud rate).

⑥Encoder is used as a fast communication in the master station mode, PLC is used as a slave station, and the encoder broadcasts data continuously to the PLC. The protocol content is simple, the decoding is fast and does not occupy much resources. The baud rate of 19200 is 8mS once data refresh , 115200 baud rate is 2mS once data refresh

⑦PLC switch point input is used as an absolute encoder connection interface: this method is only used for absolute single-turn encoders with 10 bits or less. Absolute encoders with more digits generally occupy more switch points, especially 12 bits The above absolute value encoder is no longer suitable, and it is now a relatively backward connection method for absolute value encoders and is no longer recommended.