How to Enable Remote SSH Access for Industrial Shields RPi PLCs

1. The Off-Grid Connectivity Challenge

Industrial Shields provides fantastic hardware flexibility by packaging Raspberry Pi and Arduino boards into rugged, industrial-grade PLCs. Typically system integrators use these devices in remote environments – such as smart irrigation systems, solar microgrids or wastewater lift stations.

Connectivity remains the main challenge of these deployments. There is rarely a fiber or broadband connection available in the middle of a field. If a logic error occurs or code needs updating, dispatching an engineer to manually plug into the PLC’s ethernet port is costly and inefficient. You need a reliable cellular tunnel.

2. Hardware Setup: Plug and Play

To provide cellular backhaul, we will pair the Industrial Shields PLC with a Valtoris 4G LTE Industrial Gateway.

• Power: Both devices accept standard 12V/24V DC DIN-rail power supplies.
• Network: Connect a standard RJ45 Ethernet cable from the ethernet port on the Raspberry Pi PLC to any of the LAN ports (LAN1-LAN4) on the Valtoris router.

3. Network Configuration: Setting Up Port Forwarding

The PLC can access the internet, but by default you cannot access the PLC from the outside because of the NAT firewall on the router. Port Forwarding must be setup to allow remote SSH access to get the install code.

Log into the Valtoris web interface (Default: 192.168.8.1) and go to Network > Firewall > Port Forwards. Create a new rule to forward incoming external traffic to the internal PLC.

Figure 1: Mapping external port 2222 to the internal RPi PLC’s Port 22 (SSH).

Configuration Parameters:

• Name: SSH_to_RPi_PLC (or any identifiable name)
• Protocol: TCP
• Source Zone: wan (Incoming 4G cellular traffic)
• External Port: Choose a custom port (e.g., 2222) to obscure standard SSH ports from basic bot scans.
• Destination Zone: lan
• Internal IP Address: Select the local IP assigned to your Industrial Shields PLC (e.g., 192.168.8.182).
• Internal Port: 22 (Standard Linux SSH port)

4. The Result: Secure Remote Terminal Access

When you save and apply the rule, your remote infrastructure is ready to go. The system integrator can now start a terminal from their office anywhere in the world and run:

Traffic is transparently routed from the cellular network, through the Valtoris NAT firewall, straight into the Raspberry Pi logic controller – no costly site visits for software updates or diagnostic debugging.