Product Overview

The Schneider HMISTU655 Harmony STO & STU Colour Touch Panel Screen is a compact human-machine interface (HMI) for machine operation, process visualization and local equipment monitoring. It uses a 3.5-inch color TFT touchscreen with a 320 × 240 pixel QVGA resolution, providing an operator interface for machines that need clear status information without a large panel display.

The HMISTU655 uses a modular installation arrangement based on a 22 mm mounting hole. Unlike conventional HMI terminals that require a rectangular panel cutout, this design can simplify installation on compact machine panels and equipment enclosures. It is useful for machine builders working with limited panel space or retrofitting an operator interface into an existing control station.

For example, a small pumping system may need a local screen to show operating status, measured values, alarm messages and permitted start or stop commands. The HMISTU655 can display these items through a configured HMI application while communicating with a compatible controller over its serial or Ethernet interface.

The terminal supports Vijeo Designer for application development. Screen layouts, numerical displays, alarm pages and operator controls are configured according to the connected PLC and machine requirements. Correct selection therefore depends on the existing application, communication protocol, mounting arrangement and controller compatibility.

The HMISTU655 is an operator interface, not a standalone PLC. Machine sequencing, equipment interlocks and safety-related control remain the responsibility of the appropriate controller and safety equipment.

Technical Specifications

Product Features

• 3.5-inch color touchscreen: Displays machine status, process values, alarm messages and operator controls.
• QVGA display resolution: Supports compact graphical screens for basic machine operation and monitoring.
• Modular mounting design: Uses a 22 mm mounting hole, reducing the need for a conventional rectangular panel cutout.
• Serial communication: Supports RS-232C and RS-485 connections for compatible controllers and automation devices.
• Ethernet connectivity: Supports network communication through the integrated Ethernet interface.
• Vijeo Designer software: Provides the environment for creating and maintaining HMI applications.
• USB connectivity: Provides host and device ports for supported peripherals and engineering tasks.
• Analog resistive touch: Allows operators to interact with configured screen objects through direct touch.
• Front-panel protection: Supports industrial panel installation when the mounting and sealing requirements are met.

Working Principle

The HMISTU655 acts as the operator interface between a machine and its control system. Its application defines the screens, values, alarms and controls presented to the operator, while the connected PLC or controller executes the actual machine logic.

During operation, the HMI exchanges data with the controller through the configured serial or Ethernet connection. It reads variables for display and sends permitted operator inputs back to the controller. The controller then evaluates those inputs against its programmed conditions before changing machine operation.

Consider a compact material-handling machine with a conveyor motor and several position sensors. The HMISTU655 can show the conveyor state, sensor status, operating mode and fault messages. An operator may select an available operating command or change a permitted setting, while the PLC handles sequencing, motor control and interlocks.

Communication depends on the selected protocol, network or serial settings, controller configuration and application data mapping. A screen may remain operational even when the controller connection has failed, so displayed values and communication status should be checked during commissioning.

The terminal does not independently perform the control functions assigned to the PLC or replace safety-rated equipment. It provides the visual interface through which operators monitor and interact with those systems.

Role in a Harmony STO & STU Machine Control System

The HMISTU655 provides the local visualization and operator-input layer in a compact automation system. Its modular mounting arrangement suits installations where the HMI must fit into a limited panel area.

Operator Input → HMISTU655 HMI Application → Serial / Ethernet Communication → PLC or Controller → Machine Equipment

Industrial Applications

Installation and Maintenance

1. Verify the model number: Confirm that HMISTU655 matches the required display, communication interfaces and mounting arrangement.
2. Check the panel mounting location: Ensure the installation provides the specified 22 mm mounting hole and sufficient clearance for the terminal assembly.
3. Confirm the power supply: Provide a compatible 24 V DC supply within the specified 20.4–28.8 V range.
4. Select the communication interface: Determine whether the controller connection uses RS-232C, RS-485 or Ethernet.
5. Configure the communication parameters: Match the selected protocol, addressing and other required settings to the connected controller.
6. Prepare the HMI application: Verify that the project is developed in Vijeo Designer and matches the installed terminal configuration.
7. Check controller variables: Confirm that the HMI data addresses and data types correspond to the controller program.
8. Inspect the connectors: Check the power terminals, RJ45 connectors and USB ports for damage or loose connections.
9. Secure the terminal: Install the unit according to the specified mounting procedure and check that the required sealing is maintained.
10. Transfer and test the application: Load the approved project using a supported transfer method and verify screen navigation and data updates.
11. Test operator functions: Check configured buttons, numerical entries, alarms and permitted commands under controlled conditions.
12. Record maintenance findings: Document the terminal model, application revision, communication settings and any changes made during servicing.

Compatible System Components

Recommended Related Models

Key Advantages

• Combines a color touchscreen with serial and Ethernet communication.
• Uses a 22 mm mounting hole for a compact installation arrangement.
• Supports Vijeo Designer HMI application development.
• Displays machine status, process values and alarms through configured screens.
• Provides USB connectivity for supported engineering and peripheral tasks.

Technical FAQs

What distinguishes the HMISTU655 from the HMISTO715?

The HMISTU655 uses a 3.5-inch color touchscreen and a modular mounting arrangement based on a 22 mm hole. The HMISTO715 uses a 4.3-inch display and a different panel installation design. Their communication interfaces and application configurations should also be checked before selecting a replacement.

Which software is used to configure the HMISTU655?

The HMISTU655 uses Vijeo Designer. The project should match the terminal configuration and contain the correct controller driver, communication settings, screen definitions and variable assignments.

Can the HMISTU655 communicate with a controller over Ethernet?

Yes. The terminal includes an Ethernet interface supporting 10BASE-T/100BASE-TX. Communication depends on the controller protocol, network configuration and the settings defined in the HMI application.

What should be checked if the HMI displays incorrect process values?

Check the controller connection, protocol settings, variable addresses, data types and scaling. If the HMI values match the controller data but the physical measurement is incorrect, investigate the field instrument and control loop separately.