Build Modbus PLC InfluxDB Logger

Build an industrial Modbus telemetry pipeline: poll PLC holding registers on a schedule and write readings to InfluxDB for dashboards and alerting.

What this template does

1. Every Minute — Cron Schedule trigger.
2. Read PLC Registers — Modbus TCP Request (holding registers).
3. Write to InfluxDB — time-series point with tags for PLC identity.

Step 1 — Load the template

1. Studio → Templates → search Modbus PLC InfluxDB or IoT Automation.
2. Load template #128. Confirm the cloud badge shows on-prem requirement on Modbus nodes.

Step 2 — PLC connection

1. Select Read PLC Registers. Set Host to your PLC IP (e.g. 192.168.1.10).
2. Configure Unit ID, Start address, Count, and Data type per your device manual.
3. Use Direct connect — no Discovery scan required for Modbus TCP.

Step 3 — InfluxDB

1. Select Write to InfluxDB. Set URL, token, org, bucket, and measurement name.
2. Map Value from {{values}} or a specific register index.
3. Store credentials in {{$var.influxToken}} rather than plain text when possible.

Step 4 — Schedule

1. Adjust the cron expression if one minute is too aggressive for your PLC.
2. Example: */5 * * * * for every five minutes.

Step 5 — Test on-prem

1. Run from an on-prem Studio host or exported runtime on the same subnet as the PLC.
2. Dry Run validates graph wiring; live Modbus requires activation.
3. Check InfluxDB for new points and Jobs → History for run traces.

Deploy to edge

For factory gateways, export the runtime agent and install as a Windows/Linux service. The agent polls locally — no cloud hop for PLC traffic.

Related tutorials

• Modbus Threshold → Slack Alert — alert when a register exceeds limits.
• File Drop Automation — another on-prem pattern.
• Modbus TCP Request — node reference.