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How to connect small PLC to servo encoder signal?

2021-01-11 H:37:30
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Weihai Adike Electronic Technology Co., Ltd. is mainly engaged in servo encoders, mechanical multi-turn absolute encoders, industrial Ethernet encoders and other types of encoders. Welcome to contact Adike Electronics at any time! Satisfactory service for customers is the primary purpose of Adike!


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


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


③RS485 signal enters the communication interface of the PLC (one communication port is required, if the PLC communication port is also connected to other devices such as touch screen, you need to select more than 2 communication ports when purchasing PLC). There are generally two RS485 interfaces of N80, the high baud rate reaches 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. 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, and an encoder generally takes up 50mS or more.


⑤ 485 Modbus absolute value encoder manufacturer's own Easypro free protocol, PLC as the master station, the encoder as the bus type connection of the slave station, you can connect multiple (1-9) Easypro encoders. The PLC needs to configure the communication program, baud rate, data bit format, etc. If the data is in ASCII code, it is necessary to call the ASCII decoding command that comes with the PLC. This feature is simplified than modbusRTU and saves PLC resources. Each encoder takes about 30ms (19200 baud rate).


⑥Encoder is used as a master station for fast communication, PLC is used as a slave station, and the encoder broadcasts continuously to send data to the PLC. The protocol content is simple, the decoding is fast and does not occupy much resources. The 19200 baud rate is 8mS for one 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.


CANopen绝对值编码器


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