Siemens DP communication fault method

Siemens Profibus DP communication is often used for communication between PLC and other PLCs, remote substations, frequency converters, bus instruments and third-party DP equipment. The program is simple and the wiring is convenient. However, once the red light on the DP network is always on or flashing, it is also a very annoying thing. It can cause the station to be dropped, or the entire network to be paralyzed. Sometimes a small fault may take a lot of time to eliminate. Today, Let’s talk in detail about the steps to quickly troubleshoot DP communication failures.

Step 1: Find the fault point in the DP network

After a DP alarm appears on the system:

(1) Principle of adding stations one by one: first get rid of all faulty segment slave stations, and start diagnosis from the first normal DP station closest to the CPU on the DP network.

(2) If only one station on the entire line alarms, directly determine that station to be the location of the communication failure.

(3) If only a certain section of the entire line has an alarm, continue to use (1) method to diagnose the fault section.

(4) If the entire line alarms, directly use the method (1) to diagnose.

Note: When stripping off the rear slave station, you can turn the DP switch of the station to the ON position or directly remove the DP outlet of the station.

Step 2: Find the fault source at the DP site

After determining that the site is faulty:

(1) The station software settings are incorrect: DP address, module model, baud rate setting

(2) The station module has been damaged: DP module, bus slot

(3) Communication interface failure of the station: DP connector incoming line, DP incoming line

(4) Communication interface failure on the upper station: DP connector outlet, DP outlet

(5) If SFC51 gives an alarm message, the 24V power supply of the slave station may be faulty.

Step 3: Repair the fault source at the DP site

(1) The software setting of this station is wrong: DP address, module model and configuration must be consistent

(2) The station module has been damaged: the DP module and bus slot must be exchanged or replaced.

(3) Communication interface failure of the station: DP connector and DP cable repair or replacement

(4) Communication interface failure on the upper station: DP connector and DP cable repair or replacement

(5) The power module of the station is faulty: replace the power module

Step 4: Repair DP communication instability

(1) Check the system communication load: total number of sites, communication distance, bus baud rate, etc.

(2) Check system communication interference: system grounding, power isolation, DP line grounding, etc.

(3) Interference from other communication equipment: software, hardware and wiring of third-party DP stations, etc.

Precautions:

(1) Both the incoming and outgoing ends of the DP connector may be damaged.

(2) Oxidation of the terminal of the DP cable may also cause communication failure.

(3) The grounding of DP cable wiring must be reliable, and the ground wire and DP wire must not come into contact

(4) Pay attention to the total number of DP stations linked to various CPUs. Exceeding the capacity will also cause failures.

(5) When the DP line is far away, a repeater or RS485 active terminal can be added

Attached table: Theoretical relationship between DP transmission distance and baud rate:

The above is about ” Siemens DP communication failure methods “. I hope it will be helpful to you. Author: Toutiao-Jicheng PLC Classroom.

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