Industrial
Dependable interconnects for industrial control system HMIs
Frequently situated in unforgiving environments, the HMIs and control panels of machines in industrial plant settings – from manufacturing and automation to food processing or power generation – must be able to cope with harsh conditions. These range from excessive vibration or shock to electrical noise and interference, as well as extremes of temperature or humidity, plus exposure to aggressive media or particulate matter. Equipment should also ideally be easily wipe-clean and resistant to high-pressure steam cleaning and washdown protocols. UK managing director at interconnect design & manufacturing specialist, Nicomatic, Phil McDavitt explains here how interconnect technologies such as membrane switches & FFCs help enable reliable HMIs in industrial applications
M
achines and industrial automation equipment (including robotics) found in production settings, such as manufacturing, assembly
and processing plants, typically require some type of interactive control system in the form of an HMI (human-machine interface). Its primary purpose is to display real-time process data and provide a means for operators to interact with the control system. While back-office systems usually feature familiar standard electronic IT (information technology) and computing kit (including, for instance, PCs, keyboards and mice, touchscreens and displays), HMIs on factory shop floors must be more rugged, combining ease-of-use with a sturdy form factor that can deal with the rigour and extremes of industrial environments. Displays and touchscreen panels, indicators in the form of lamps or LEDs (light-emitting diodes), membrane switch keypads, and electromechanical controls (including sliders, switches, buttons, dials and joysticks) are more commonly employed interfaces in industrial automation settings. They offer greater robustness, simpler and more reliable ease-of-use, and longer service lifetimes. Safety and ergonomics are also key factors, with HMIs often mounted on adjustable arms that swing or swivel to ensure operators are safe and comfortable – while stack lights help make monitoring visual alerts quick and easy.
How much force will a typical user press the switch with? And how much tactile feedback does the user need?
How many cycles will the dome be used for? Will the switch last the expected lifetime of the HMI?
Novel approaches address design challenges
IP-rated protection guarantees resistance to extreme environmental influences, including the unintentional ingress of foreign bodies, including dust, dirt, liquids, moisture and even aggressive media (such as oils or chemicals). All these various controls, displays and indicators depend on signals and power. Reliable interconnects play a vital role in providing the proven mechanical, electrical and environmental performance needed – often in space-constrained form factors.
‘Under the hood’, flat flexible cables (FFCs) can provide the board-to-board connections needed between the electrical switches and other sub-assemblies and PCBs (printed circuit boards) in the system, integrating cables into complete interconnect solutions. FFCs offer mechanically strong, lightweight, reliable signal and power connections, alongside significant space savings and easier cable management. They can also provide superior
Membrane switches
With electrical switches deployed throughout diverse applications and environments, many factors can affect their lifecycle, which may vary considerably from that achieved under strictly controlled laboratory testing conditions. Metal domes are used in membrane switch keypads to enable the electrical connection from the switch or keypad, enabling end-users to initiate specific functions. The switch domes are mounted on PCBs, FPCs (flexible printed circuits) or silver- printed flex membranes.
To ensure the most suitable dome is selected for each application and environment, design engineers should consider: What size and shape of dome fits the application?
What environment will the HMI be deployed in?
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shielding, which is crucial in electrically noisy environments (exacerbated by the multitude of power cabling, communications networks and motors found in industrial settings). Nicomatic-patented Crimpflex connectors provide solid, dependable electrical and mechanical connections between the FFCs and other system components, while its V Shield FFC range delivers both dynamic flexing and EMI (electromagnetic interference)/RFI (radio frequency interference) and ESD (electrostatic discharge) protection.
New approaches in dome technology can help solve common problems. Nicomatic’s patented Switch’Air Domes are four-legged metal domes with a notch that creates a cushion of air between the domes to prevent them sticking to each other, a common issue. They are also very low profile, making them ideal for many domestic products, including microwave ovens, dishwashers and washing machines – as well as industrial HMI control panels. They are even used in cash machines – a consumer application in which users take robustly functioning keys for granted!
Reliable technologies for industrial control interfaces
HMIs and control panels in manufacturing production, processing and industrial automation applications must often endure harsh environments, ranging from extremes of vibration, temperature, humidity and electrical noise to frequent exposure to grease, dirt and debris. To ensure robust and reliable operation, they employ interface technologies that can handle these demanding requirements – including ruggedized touch panels, electromechanical controls and membrane switches. FFCs provide the connectivity between these system elements, delivering both signals and power. Interconnect specialist, Nicomatic can help design engineers identify and specify the ideal components for such HMI systems.
https://www.nicomatic.com/ Components in Electronics September 2023 17
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