M91-2-RA22 Unitronics M91 Textual display and keyboard HMI and PLC onboard I/Os expands up to 150 I/Os

Why Choose the Unitronics M91-2-RA22 Micro PLC with Integrated Text HMI?

The Unitronics M91-2-RA22 is a compact micro PLC with integrated text-based HMI from the Unitronics M90/M91 series, designed for small and medium industrial automation systems. The controller combines programmable logic control, operator interface and onboard I/O in a single device, helping reduce control panel complexity while lowering installation and maintenance costs.

The controller features a built-in two-line LCD display capable of showing 16 characters per line with a 15-key operator keypad. This allows operators to monitor machine status, navigate menus and configure parameters directly from the front panel without requiring a separate HMI unit.

The M91-2-RA22 offers a flexible I/O configuration including digital, analogue and temperature inputs together with relay and analogue outputs. It also supports RS232 and RS485 communications, enabling integration with PLC networks, SCADA systems and industrial monitoring platforms.

Key Features

• All-in-one PLC with integrated text HMI and keypad interface.
• 2-line LCD display with 16 characters per line.
• 12 digital inputs including a high-speed counter input.
• 2 analogue inputs supporting voltage or current signals.
• 2 temperature inputs supporting PT100 or thermocouple sensors.
• 8 relay outputs for switching industrial loads.
• 2 analogue outputs for process control signals.
• RS232 / RS485 communication supporting Modbus protocols.
• I/O expansion capability for additional modules.

Technical Specifications

• Manufacturer: Unitronics
• Series: M90 / M91
• Model: M91-2-RA22
• Controller type: Micro PLC with integrated text HMI
• Display: STN LCD monochrome display with LED backlight
• Display size: 2 lines × 16 characters
• Keypad: 15 operator keys
• Supply voltage: 24 V DC (20.4 to 28.8 V DC)
• Digital inputs: 11 standard inputs + 1 high-speed counter input
• Analogue inputs: 2 inputs (0–10 V, 0–20 mA, 4–20 mA)
• Temperature inputs: 2 inputs (PT100 or thermocouple)
• Relay outputs: 8 SPST-NO relay outputs
• Analogue outputs: 2 outputs (0–10 V or 4–20 mA)
• Communication: RS232 and RS485 serial ports
• Program capacity: approx. 36 kB ladder logic
• Expansion capability: supports expansion modules up to approximately 150 I/O points
• Protection rating: IP65 / NEMA 4X front panel
• Operating temperature: 0 °C to 50 °C

Typical Applications

• Small machine automation systems.
• Water treatment and pump control.
• Packaging and material handling equipment.
• Industrial process monitoring and temperature control.
• Standalone automation systems requiring simple operator interface.

Trusted by Machine Builders

Unitronics M90 and M91 series PLCs are widely used in industrial automation because they combine PLC logic control and operator interface in a compact, cost-effective platform suitable for machine builders and panel builders.