Why Raspberry Pi in Factories?
A Raspberry Pi 4 (4GB RAM) costs ₹5,000–7,000 and can run Python, Node.js, MQTT, and a small database simultaneously. It has GPIO pins for direct sensor connections, USB ports for serial adapters (RS-485/RS-232), and Ethernet for PLC communication. For many factory IoT use cases, it outperforms PLCs at 10% of the cost.
Hardening for Industrial Use
Factory environments have power fluctuations, vibration, dust, and temperature extremes. Use read-only file system mode (overlayFS) to prevent SD card corruption on power loss. Install in a DIN-rail mounted industrial enclosure with passive cooling. Use industrial-grade SD cards (SLC NAND, not consumer TLC). Add a UPS or battery backup for graceful shutdown.
Connecting to PLCs via RS-485
Most legacy PLCs have RS-485 Modbus ports. Use a USB-to-RS-485 adapter (₹500–1,500) on the Raspberry Pi. Install the pymodbus Python library. Configure baud rate, parity, and stop bits to match the PLC (check the manual). Test with a Modbus master tool before writing integration code.
Reliability and Watchdog
Enable the hardware watchdog — if the main process hangs, the watchdog resets the Pi after 15 seconds. Use systemd service files for your gateway application so it restarts automatically on crash. Log all restarts with timestamps. In our deployments, properly configured Raspberry Pi gateways run for 18+ months without manual intervention.
A properly hardened Raspberry Pi 4 in an industrial enclosure with watchdog and read-only filesystem is a reliable industrial edge device at a fraction of industrial PC cost.
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