Question 1

How do I configure node-red-contrib-s7 with a Siemens S7-1500 PLC?

Accepted Answer

First, on the PLC, disable 'Optimized block access' for relevant data blocks and enable 'Permit access with PUT/GET' in the CPU properties. Then, in Node-RED, create an S7 Endpoint node with the PLC's IP address and define variables using the addressing scheme from the README.

Question 2

What's the difference between node-red-contrib-s7 and node-red-contrib-modbus?

Accepted Answer

node-red-contrib-s7 is specialized for Siemens S7 PLCs using the S7 protocol, with detailed addressing for S7-specific data types. node-red-contrib-modbus handles Modbus devices, a different protocol common in various industrial equipment. Choose based on your PLC brand and protocol needs.

Question 3

Can I write data to PLCs using this node?

Accepted Answer

The README focuses on reading capabilities, but writing is implied through similar addressing. However, it's not detailed extensively, so users may need to experiment or seek community support for reliable write operations, especially for complex data types.

Question 4

How to handle timestamps from S7 PLCs in Node-RED?

Accepted Answer

Use addresses like DB1,DT0 for DATE_AND_TIME formats, but note that JavaScript Dates are always UTC. For proper timezone conversion, integrate additional nodes like node-red-contrib-moment, as recommended in the README's addressing notes.

Question 5

Is node-red-contrib-s7 good for high-speed data logging?

Accepted Answer

It supports polling cycles and diff mode to optimize traffic, but for very high-frequency logging, the polling-based approach may introduce latency. Consider the cycle time settings and message modes carefully to balance performance with data accuracy.

Question 6

What are common errors when setting up this node?

Accepted Answer

Common issues include incorrect addressing due to the non-standard scheme, forgetting PLC configuration steps for S7-1200/1500, and excessive message traffic in 'All variables, one per message' mode without diff enabled. Always double-check the README examples and PLC settings.

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