Tips for Troubleshooting Industrial Communication

Troubleshooting a Missing Incoming Signal to a Controller 9 Steps That Will Make You a Pro and Help You Solve More Painful Problems When a controller fails to receive an expected signal, it can lead to system malfunctions, downtime, and frustration. A systematic troubleshooting approach is essential to pinpoint and resolve the root cause efficiently. Here are nine expert steps to diagnose and fix a missing incoming signal like a pro. 1️⃣ Verify System Status & Symptoms Check if there are any error indicators on the controller. Determine if the issue is isolated to one signal or affecting multiple inputs. 2️⃣ Review System Documentation Refer to wiring diagrams and the controller's manual to understand the signal path. Identify the source of the missing signal and its expected voltage or communication method. 3️⃣ Inspect Physical Wiring & Connections Check for loose, broken, or disconnected wires between the source and the controller. Inspect terminal blocks for corrosion, damage, or loose screws. Verify that connectors are properly seated and that the wire is fully inserted. 4️⃣ Measure the Signal at the Source and Input Terminal Use a multimeter to check voltage levels at different points along the signal path. If using an oscilloscope, check for signal integrity and possible noise issues. 5️⃣ Check for Power & Grounding Issues Ensure the power supply to both the controller and the signal source is stable and within specification. Verify proper grounding and check for ground loops that may interfere with signal transmission. 6️⃣ Test the Signal Source If applicable, manually activate the device sending the signal (e.g., switch, relay, sensor). Bypass the sensor or input device by applying a test voltage to the controller input to see if it registers. 7️⃣ Check Software & Programming Verify that the controller’s logic or programming is expecting the signal at the correct input. Look for incorrect parameter settings, disabled inputs, or software overrides that may block the signal. 8️⃣ Swap or Replace Suspected Faulty Components If software, wiring, and the signal source check out, troubleshoot the controller’s input side. Replace any damaged relays, sensors, interface modules, or PCB boards. 9️⃣ Final Verification and Documentation After identifying and fixing the issue, monitor the system to ensure the signal remains stable. Document the root cause and corrective action to prevent future occurrences and aid in future troubleshooting efforts.

Tech Tip Tuesday 🔧💡 When you’re integrating PLCs from different vendors — like Allen-Bradley ↔ Siemens — the very first thing you should do is: 👉 Map out all communication protocols, IP addresses, and data types — before you touch a wire or start writing logic. Whether it’s EtherNet/IP, Profinet, Modbus TCP, or OPC UA — knowing what speaks what will save you from hours of troubleshooting weird comms issues, mismatched tags, or inconsistent updates later. 🧠💻 ✅ Document your data map ✅ Test communications early ✅ Use diagnostics tools from each vendor Trust me — the time you spend up front mapping protocols is nothing compared to what you’ll spend if you skip it. Integration starts with communication — literally. #TechTipTuesday #PLCIntegration #AllenBradley #SiemensPLC #Modbus #Profinet #EtherNetIP #IndustrialAutomation #ControlsEngineering #SystemIntegration #ELEKproTEK #AutomationTips #PLCProgramming #SCADA #OTNetworking #SmartTechMoves 🧠🔌📡

💡 Wireshark Ring Buffer I've mentioned in previous posts that "rolling wireshark captures are a gift". What the heck was I talking about? As you can imagine we get lots of phone calls regarding network "ghosts", some network event that happens but sporadic/unpredicatable in nature insofar as frequency of re-occurrence. That leaves us with two choices to troubleshoot: 1) Take up residence sitting on a wirespool and "hope" the event occurs while we are sitting there capturing (not too practical in most cases) 2) Utilize Wireshark's Ring Buffer feature. Per the Capture Option screenshot below, you can select multiple options to turn a computer with Wireshark effectively into a Network DVR. Extra Tips: 1) Ensure the Wireshark PC time is correct before getting started. Especially when helping remotely working with local personnel for the captures, this will be crucial when they contact to say "the event just happened at 9:58a" that they can easily identify the captured file that includes the event and send back for analysis. 2) Do a quick test with a ~2 minute capture to determine the resulting file size, then do some math between that file size and available hard drive space to figure out what you're working with from a storage perspective. Generally speaking we find we can record a ring buffer of an entire day+ if needed. 3) Pick a reasonable ceiling for the max file size option. While you may be inclined to set a large size here, you'll find that working with PCAPs even in the triple digit MB range can sometimes be cumbersome when crunching various analytics in Wireshark. #industrialnetworking #otnetworking #wiresharkringbuffer