HMI devices are an important part of automation systems. HMIs enable humans to interact with machines efficiently. Maintaining The HMI is important to maintain good machine or system performance under good operating conditions.
But like other hardware devices, HMIs are prone to failures that can render the machine inoperable or interrupt the system. The next section describes some of the most common HMI failures and troubleshooting methods for each situation.
HMI-PLC communication problems
The HMI needs to be in constant communication with the host controller (in most cases, a programmable logic controller or PLC). Several protocols can be established based on Ethernet and Ethernet-based foundations. The serial protocol is the most popular.
When the HMI and PLC When communication fails, the HMI will not be able to read and write files in The HMI function specifies the PLC tag machine status is the ability of the machine to not operate in manual or teach mode. If another external failure occurs that requires human intervention, the machine will stop technical service due to loss of HMI communication.
Intermittent HMI-PLC Eliminate communication problems failure
Based on the Ethernet HMI-PLC protocol, one of the first recommended diagnostic steps is to operate a simple ping command from both ends to confirm the fault, if supported by the device. ping responses are intermittent and other times not at all.
Intermittent responses may indicate a loose connection at one or both terminals. If RJ45 termination is used, it may need to be re-crimped. It is useful to use a voltmeter to check both ends of each pin continuously. This will help identify problems with specific wires and is applicable to any connector.
If the wiring and terminals are in good condition, the problem may be software related. the Wireshark packet sniffer can help determine if there is a data transmission problem. For example, if there are duplicate IP addresses in the network, or if two devices are trying to use the same TCP/IP port incorrectly may cause intermittency.
Some systems use Network Address Translation (NAT) routing to simplify and modularize machine networks. In these systems, hardware devices that are allowed to communicate over Ethernet have the same IP address. This is true as long as all IP addresses are unique within each subnet. Therefore, it is important to carefully complete the NAT configuration to properly isolate each subnet. In this case, if there is a NAT problem is, packets will be helpful to the sniffer.