48,000 rows is what a Raspberry Pi reading 20 tags a second has to hold through a 40-minute outage, and the SQLite file that held them in the run behind this article was 5.3 MB, including the write-ahead log. That is the size of the buffering PLC data problem, and it is small. What is … Read more
A Docker Raspberry Pi that stopped logging on a Sunday had /var/lib/docker/containers/3f9a…/3f9a…-json.log at 22 GB when du got to it, and the file belongs to a container whose only job was to reconnect to a broker that had been down since Thursday. Docker’s default log driver is json-file, its default max-size is unlimited, and a … Read more
PLC data logging that stays useful: sampling rates, retention math, a ring buffer in the controller, FactoryTalk datalog, SQL logging, safe remote access.
What an Industry 4.0 project really changes on the PLC: the OPC UA server, a UDT to JSON data model, MQTT at the edge, retrofits and security.
A working IIoT setup for a plant floor PLC: edge gateway choice, MQTT and Sparkplug B topics, a decoded payload, store and forward, deadbands and security.