How to select an HMI and remote I/O

In short:Size the HMI from what the operator must see and touch at once (typically 7 to 10 inch for a single machine, larger for lines), confirm its drivers for your controller, its front rating as installed and its operating temperature, then place remote I/O where the sensors are, on EtherCAT when I/O is part of the machine cycle and on Modbus RTU or TCP only for slow signals, and plan IIoT access with outbound, authenticated connections.

Where the HMI and remote I/O fit

The controller runs the machine; the HMI is how operators and maintenance staff see and change what it does; remote I/O puts the inputs and outputs near the sensors and actuators instead of in the main cabinet. All three are chosen together because they share a network and a software environment.

Make the decisions in this order:

1. Controller and network: what the HMI and I/O must talk to.
2. HMI size and resolution: from what must be visible at once.
3. HMI hardware: touch type, brightness, front rating, temperature, mounting.
4. HMI software and drivers: protocols, recipes, alarms, users.
5. Remote I/O: where, how many points, which signal types.
6. I/O network: EtherCAT, Profinet, CANopen or Modbus, by update time.
7. IIoT and remote access: what leaves the machine, and how securely.

For the controller itself, see how to select a motion controller or PLC.

HMI screen size and resolution

Start with content, not catalogue sizes. List what the operator needs on the main screen without paging: process values, start/stop and mode controls, the active alarm, and the counter or recipe in use. Then sketch it at the touch-target size gloved fingers need. That sets the minimum screen.

Typical outcomes:

Resolution sets how much detail fits. Pixel density = √(width² + height²) ÷ diagonal:

• 7 inch at 800 × 480: about 133 ppi
• 10.1 inch at 1024 × 600: about 118 ppi
• 15.6 inch at 1920 × 1080: about 141 ppi

A higher-resolution panel of the same size shows more, but text and buttons shrink unless the screens are redesigned. If several sizes are used across a machine family, choose a range where one project scales across sizes; Kinco says a single MASS project is portable across its 4.3, 7 and 10.1 inch panels.

HMI hardware: touch, brightness, front rating and temperature

Touch technology. Resistive touch works with gloves and styluses and tolerates water on the screen; Kinco’s GL070, for example, uses a 4-wire resistive panel. Projected capacitive gives a glass front and multi-touch but may need conductive gloves and can misread water. Choose by what operators wear and how the screen gets wet.

Brightness. Kinco’s GL070 is 250 cd/m² (Kinco GL070), typical for indoor panels. Near windows or outdoors, ask for a high-brightness version and check it in the actual light.

Front rating. IP65 on an HMI is normally the front face, as installed. Kinco’s GL070 specifies IP65 for the front panel. The rating depends on:

• the cut-out being to the stated size and tolerance (192 × 138 mm for the 7 inch GL070),
• the gasket being fitted and evenly compressed by the clamps,
• the enclosure itself being rated at least as high,
• a flat, rigid panel that does not bow.

For washdown areas, ask specifically about the front’s jet resistance and the gasket’s chemical resistance; see hygienic washdown actuators and IP69K for what the ratings test.

Temperature. The GL070 is rated 0 to 50 °C. Cabinets in sun, near ovens or in cold stores need checking; LCDs respond slowly in cold and can be damaged by heat.

Supply and housing. Most panels run from 24 VDC (the GL070 accepts 10–28 VDC). Metal housings, as on Kinco’s FUTURE range, resist knocks better on mobile or heavy-duty machines.

Emergency stop. Some panels integrate buttons and an E-stop (Kinco’s F2156E-TX, for example). The E-stop must be hardwired into the safety circuit; a touchscreen or HMI software is not a safety device.

HMI software, drivers and protocols

The HMI must talk to your controller, natively and reliably. Check:

• Drivers: Kinco’s DTools/DToolsPro lists drivers for OMRON, Siemens, CODESYS and Rockwell controllers, among others. Confirm the exact controller family and protocol (for example Modbus TCP, EtherNet/IP or a vendor protocol).
• Ports: serial (RS232, RS485, RS422) for older PLCs and drives; one or two Ethernet ports, ideally separate for machine network and plant network.
• Functions: alarms with history, recipes, trends, user levels, data logging, screenshots, multi-language, remote viewing.
• Database and export: DTools lists links to SQLite, MySQL, SQL Server and PostgreSQL.
• Combined HMI and PLC: on small machines, an HMI with a built-in PLC, such as Kinco’s MK with high-speed pulse outputs, can remove a separate controller.

Remote I/O: where and how much

Put I/O islands where cable runs concentrate: a conveyor section, a robot cell, a pneumatic manifold. Each island replaces dozens of individual sensor cables to the cabinet with one network cable and one power cable.

Count, per island:

• digital inputs (sensors, switches) and their type (PNP or NPN),
• digital outputs (valves, lamps) and their current,
• analogue inputs and outputs (voltage, current) and resolution,
• temperature inputs (RTD, thermocouple),
• special functions (counters, encoder inputs, PWM).

Add 20% spare as a rule of thumb, and check the coupler’s limits. Kinco’s RP20, for instance, takes up to 16 modules and 256 I/O points per coupler, with digital, analogue, RTD and thermocouple modules.

For hostile locations, I/O with IP67 housings mounts directly on the machine; IP20 slice I/O like the RP20 belongs in a local enclosure.

The I/O network: EtherCAT vs Modbus and others

EtherCAT figures from the EtherCAT Technology Group.

Modbus RTU limits. The Modbus over Serial Line specification allows addresses 1–247, says 32 devices are always allowed on an RS485 segment without a repeater, gives 1,000 m maximum at 9,600 baud, and requires 9,600 and 19,200 baud with 19,200 the default (Modbus spec). Terminate both ends of the line, and only the ends (Bender).

Why Modbus RTU is slow. An RTU character is 11 bits. Reading 10 registers takes an 8-byte request and a 25-byte reply: 33 bytes × 11 bits = 363 bits, about 19 ms at 19,200 baud before inter-frame gaps and device response time. Ten such devices take a quarter of a second or more per scan. Fine for temperatures; wrong for a sensor that starts a move.

If the motion controller is EtherCAT, putting the I/O on the same EtherCAT network keeps sensor-to-axis timing in one cycle. Kinco’s AK controller expands with RP20 I/O, and Leadshine’s MC500 with up to 32 R2 modules.

IIoT and remote access

Decide what data leaves the machine, to whom, and how:

• OPC UA is the common way to expose structured machine data to site systems; Leadshine’s MC500 controller supports it.
• MQTT is publish/subscribe through a broker: devices publish data, typically when values change, and consumers subscribe (HiveMQ). Kinco’s GW01 gateway publishes to the cloud over MQTT and supports over 300 industrial protocols on the machine side.
• Remote access for support: Kinco’s GL2 HMIs offer Wi-Fi or 4G with EdgeAccess remote access; the M-IoT remote monitoring platform adds dashboards, alerts and remote control of Kinco HMIs, PLCs and servo systems.

Security basics: prefer connections the machine makes outward, so the plant firewall does not need inbound ports open; use named accounts and roles, not a shared password; separate the machine network from the plant network; and agree with the end user’s IT team who controls remote sessions. Industrial cyber-security practice is set out in the IEC 62443 series.

Worked example: packaging machine HMI and I/O

Requirement. A case packer with an EtherCAT motion controller and six servo axes. One operator station. Two remote areas: an infeed 25 m from the cabinet (24 PNP sensors, 12 valve outputs, 2 analogue inputs) and a glue station 40 m away (16 inputs, 8 outputs, 4 RTD temperature inputs). Operators wear gloves. Recipes for 30 case sizes. The customer wants remote support and an OEE feed to their site system.

HMI. The main screen needs mode controls, speed, counts, the active alarm and a machine overview. A 7 inch panel would need paging; a 10 inch at 1024 × 600 fits it. Gloves point to resistive touch. Front IP65 in a stainless enclosure with the specified cut-out. Drivers for the controller confirmed; recipes and alarm history in the HMI.

Remote I/O, infeed. 24 DI + 12 DO + 2 AI. Plus 20% spare: about 29 DI, 15 DO, 3 AI. On 16-channel digital modules that is 2 DI, 1 DO and 1 analogue module: 4 modules, well inside 16 modules and 256 points.

Remote I/O, glue station. 16 DI + 8 DO + 4 RTD, plus spare: 20 DI, 10 DO, 5 RTD: 2 DI, 1 DO and 2 RTD modules.

Network. Infeed sensors trigger axis moves, so EtherCAT for both islands, daisy-chained from the controller: 25 m and a further 15 m, inside the 100 m node spacing. The RTDs are slow but share the island; no separate Modbus line is needed.

IIoT. OEE counts published over MQTT through a gateway, or exposed on OPC UA if the site system prefers it. Remote support through an outbound VPN or cloud service the customer’s IT approves.

Result. A 10 inch resistive HMI on Ethernet, two RP20-style EtherCAT I/O islands in small IP65 boxes at the infeed and glue station, and a gateway for site data.

Products in our range to consider

• Kinco GREEN (G2 / GL2 / GH / GT / GW): connected HMI family from 4.3 to 17 inch, up to 2K resolution on G2, Wi-Fi and 4G on GL2.
• Kinco FUTURE (F2): premium HMIs from 7 to 15.6 inch up to 1920 × 1080, metal housings, version with buttons and E-stop.
• Kinco MASS (M2): lowest-cost range in 4.3, 7 and 10.1 inch at 1024 × 600, one project across sizes.
• Kinco MK: 4.3 or 7 inch HMI with built-in PLC, high-speed pulse outputs, RS485 and Ethernet.
• Kinco DTools / DToolsPro: free HMI software with drivers for major PLC brands, remote viewing and database links.
• Kinco RP20: slim remote I/O, EtherCAT coupler, up to 16 modules and 256 I/O, including RTD and thermocouple.
• Kinco GW01 gateway: IoT gateway with dual Ethernet, Wi-Fi/4G options and over 300 protocols, publishing over MQTT.
• M-IoT remote monitoring platform: cloud platform and app for monitoring, updating and recording machine data remotely.
• Kinco AK: slim EtherCAT motion controller in CODESYS for up to 32 axes with RP20 expansion.
• Leadshine MC500: CODESYS controller with EtherCAT, OPC UA, Modbus and up to 32 R2 I/O modules.

What else the build needs

• Controller with matching drivers and network: see motion controllers.
• Drives and motors on the same EtherCAT network: see servo drives and how to select a multi-axis servo drive.
• 24 VDC power supplies for HMI and I/O, with separate supplies or fusing for outputs.
• Enclosures for IP20 I/O and the HMI cut-out to the specified tolerance.
• Network cables and connectors rated for the location and any flexing; slip rings for rotating sections: see Ethernet through slip rings.
• Safety relay or controller: E-stops and guards hardwired, not via the HMI.
• Firewall or VPN router for remote access, agreed with the end user’s IT.

Things that catch engineers out

• Choosing the screen before designing the screens. Content sets size.
• IP65 front read as IP65 unit. Cut-out, gasket and enclosure decide it.
• Capacitive touch with gloves or wet hands. Check before ordering in volume.
• An E-stop on the touchscreen. It must be hardwired.
• Modbus RTU for fast signals. Polling time grows with every device.
• Unterminated or mid-line terminated RS485. Terminate the ends only.
• No spare I/O. Late sensors need somewhere to land.
• Opening inbound ports for remote access. Use outbound, authenticated connections.

Checklist

Send these to our engineers, or enter them in the spec builder:

• Controller make and model, and its networks
• HMI: content of the main screen, preferred size, number of panels
• Touch type, gloves, wet hands, brightness or outdoor use
• Front rating needed, enclosure material, washdown
• Operating temperature range
• Recipes, alarms, users, data logging, languages
• I/O count per location: DI, DO, AI, AO, RTD, thermocouple, counters
• Distances from the cabinet to each I/O location
• Which signals take part in the machine cycle and their timing
• IIoT and remote access needs, and the end user’s IT rules
• Expected annual volumes

For the wider family, see our motion controllers overview.