Networking Two Siemens LOGO! 8 with Weintek HMI on a Shared WLAN

Overview

The application involves two identical pump-control cabinets, each integrating a Siemens LOGO! 8 logic module (LOGO! 24CE), a DM16 24R digital-output expansion, and a Weintek MT8071IP 7-inch HMI. The cabinets are joined to an existing building WLAN so the LOGO! integrated web server can be reached for remote monitoring, while an unmanaged industrial switch inside each cabinet provides the local Ethernet segment for the LOGO!–HMI pair.

The principal engineering question is whether the LOGO! Soft Comfort (LSC) project must be authored in Network Project mode to avoid address conflicts between the two cabinets, or whether two independent Diagram-mode projects are sufficient. The short answer is that either mode works, because the HMI in each cabinet only needs to address its local LOGO! by IP. Two cabinets cannot collide as long as every device on the shared WLAN holds a unique IPv4 address. Network Project mode is a programming convenience, not a runtime requirement.

Hardware and Software Prerequisites

Verify that the LOGO! firmware is at the same major revision on both cabinets. Mixing LOGO! 8.0/8.1 with 8.3/8.4 changes the Modbus VM mapping and the S7 DB layout, which complicates the Weintek driver configuration.

Network Architecture Decision: Diagram vs Network Project

LSC supports two project containers:

• Diagram mode – a single LOGO! device. The program is built once and transferred to one LOGO!. A second, identical or divergent program is built in a fresh project. Programs are independent and cannot share tags.
• Network Project mode (LSC V8.0+) – a single workspace can host multiple LOGO! devices. Each appears in the project tree, and online operations (Stop/Run, upload, download, watch table) can be performed on any member. The user program for each device remains a stand-alone diagram.

Network Project mode does not change the network behaviour of the LOGO! firmware. The LOGO! continues to operate as an isolated S7/Modbus server. It does not arbitrate traffic, route packets, or synchronise I/O between cabinets. It is purely a developer ergonomics feature.

The HMI is the only device that talks to the LOGO! over Ethernet. As long as:

1. The HMI has the correct IP of its local LOGO!.
2. The LOGO! has a unique IP within the WLAN subnet.
3. No two devices share the same IP (including the Weintek panels).

… the two cabinets are logically independent and cannot collide. The WLAN simply provides a shared L2 broadcast domain and a path to the internet for the LOGO! Web server.

Recommendation: if the two pump-control programs are 100% identical and you intend to clone the LOGO! firmware, two Diagram-mode projects are the cleanest path. If the programs diverge (different pump assignments, different interlocks, different setpoints), Network Project mode keeps both in one workspace so version control, online watch, and diagnostic work happen in a single session.

IP Addressing Plan

A pump room with two cabinets commonly lives on a service VLAN or a service SSID. Plan addresses even if the building WLAN issues DHCP, and put the controls outside the DHCP pool.

Configuring the LOGO! in LSC

Diagram mode – single cabinet

1. Open LSC, File → New. The device selector offers LOGO! 24CE/8.3 or 24CE/8.4.
2. Open Tools → Ethernet Connections (or, on the device itself, Menu → Network → IP Address) and assign the static IP for Cabinet 1.
3. Build the pump-control program, click the Transfer button (PC → LOGO!), and select the Ethernet interface. LSC will discover the LOGO! over the switch and write the program.
4. Repeat the procedure in a fresh project for Cabinet 2, with its own static IP.

Network Project mode – both cabinets in one workspace

1. Open LSC, File → New, choose Network Project.
2. Right-click the project root → Add Device → LOGO! 24CE. Configure its IP and program.
3. Right-click → Add Device → LOGO! 24CE to add the second one. Configure its IP and a separate diagram.
4. Right-click each device → Connect Online to view/watch independently.
5. Programs remain independent; one device's I/O does not appear in the other's diagram.

Wiring the Cabinet Network

Each cabinet hosts the following on a shared DIN rail / cabinet-door assembly:

• LOGO! 24CE on DIN rail (left side).
• DM16 24R snapped to the right of the base module.
• 5-port unmanaged switch (e.g. Phoenix Contact FL SWITCH 1005NT).
• Weintek MT8071IP on the cabinet door.

RJ-45 cabling (T-568B throughout):

• LOGO! Ethernet RJ-45 → Switch port 1.
• Weintek MT8071IP RJ-45 → Switch port 2.
• Switch port 5 → Building WLAN bridge (or wall AP feed).

The LOGO! 8 supports Auto-MDI/MDIX, so straight or crossover cables are interchangeable. The cabinet switch should sit in the same VLAN/SSID as the WLAN if your AP supports multiple SSIDs/VLANs. Industrial protocols are not tolerant of large broadcast domains – keep the WLAN's consumer broadcast/multicast traffic (Bonjour, mDNS, AirPlay) from leaking onto the cabinet switch.

Weintek MT8071IP – EasyBuilder Pro Configuration

EasyBuilder Pro (EBPro) supports the LOGO! via two drivers. The Weintek Siemens LOGO! Ethernet PLC Connection Guide documents both paths.

Option A – Siemens S7-200 SMART (Ethernet) ISO-on-TCP, port 102

Define each tag in EBPro with:

• Address type: DB
• DB number: 1 (LOGO! 8.3+ exposes the VM area as DB1; for 8.0/8.1 use the Modbus path)
• Offset: byte address
• Data type: Word / Bool / Int as required

Option B – Modbus TCP Server (LOGO!), port 502

LOGO! 8 firmware supports a Modbus TCP server on port 502. The standard mapping is:

In EBPro, add the Modbus TCP/IP Server (LOGO!) driver:

• IP: LOGO! IP (192.168.1.51 / .52)
• Port: 502
• Slave ID: 1
• Map tags to 4x (holding) or 0x (coil) ranges

Enabling the LOGO! Web Server

LOGO! 8 ships with a built-in web server. The home page exposes status of I/Os, VM tags (read/write with password), LOGO! TD text (messages), and custom dashboards authored in LOGO! Web Editor (LWE).

1. On the LOGO!, Menu → Web Server Access → Enable.
2. Set the user password (default admin → must be changed).
3. From any browser on the same subnet: http://192.168.1.51 (or .52 for Cabinet 2).

For internet access the WLAN router must open a port to the LOGO! – preferably through a VPN tunnel rather than a direct NAT, since a publicly exposed LOGO! is a known attack vector. A small WireGuard or IPsec client on the cabinet switch side and a corresponding endpoint on the remote SCADA laptop is the field-proven pattern.

Verification and Commissioning

1. From a laptop on the same WLAN, ping 192.168.1.51 and 192.168.1.52. Both must reply with <5 ms typical latency.
2. Open LSC → Network Project → right-click Cabinet 1 LOGO! → Go Online. Verify the program version matches what was transferred.
3. In EasyBuilder Pro, click Download. The HMI must show Connected to the LOGO!, and the I/O status must update when you toggle a digital input.
4. Browse to http://192.168.1.51 from the laptop. The LOGO! home page must load and reflect the current state of VM and I/O.
5. Cycle power on the cabinet and confirm the HMI re-links within 30 seconds. The LOGO! takes ~10 s to bring up its Ethernet stack; the Weintek retries every 5 s.
6. Repeat steps 1–5 for Cabinet 2.

If the HMI shows PLC No Response, check the IP table on the Weintek (System → Network). The MT8071IP caches the PLC's IP at boot – a static IP on the HMI is therefore non-negotiable.

Troubleshooting Matrix

Field-Proven Notes

• LOGO! 8.4 firmware (6ED1052-1MD08-0BA1) exposes the VM area more cleanly over Modbus TCP than 8.0/8.1. If both cabinets will be commissioned together, flash both to the same firmware revision so the Modbus map is consistent.
• The Weintek MT8071IP is end-of-life; the cMT2078X or MT8072iP are drop-in replacements with the same project file. See the Weintek website for current product lines.
• Avoid port 80 on the LOGO! if you are also running the LOGO! Web Editor in LWE on the default port 80. Assign a non-default port (e.g. 8080) for the LOGO! web page to prevent collision.
• If the building WLAN uses 802.1X (enterprise auth), the cabinet switch will need to support MAC-auth-bypass. Most unmanaged switches will not – use a managed switch (e.g. SCALANCE XB005) with a static MAC allow-list.
• Keep the LOGO! firmware (8.3 or 8.4) consistent across both cabinets. Siemens publishes firmware updates on the Siemens Industry Online Support portal under product 6ED1052-*.
• For environments with strong RF noise (VFDs, motor rooms), prefer a wired Ethernet backhaul to the cabinet and a small AP inside the cabinet for local Wi-Fi clients only.

Frequently Asked Questions