Gemo AR2-A-24VDC-12D2A-RTC – Expandable Smart Relay / PLC with Analog Inputs, Relay Outputs and Real-Time Clock

Gemo AR2-A-24VDC-12D2A-RTC is a compact, expandable smart relay / PLC designed for machine automation, control panels and applications that require both digital logic and analog signal monitoring. It operates from a 24 VDC supply and combines 12 digital inputs, 2 analog inputs, 10 relay outputs, a dedicated PTC temperature input and a battery-backed real-time clock.

Gemo AR2 controllers have been available through our website since 2011.

Power supply and I/O

Power supply: Nominal 24 VDC, with an operating range of approximately 18–32 VDC. Maximum power consumption is 6 W.

Digital inputs: 12 inputs for 24 VDC control signals. Standard digital input filtering is at least 8 ms for both ON-to-OFF and OFF-to-ON transitions.

Analog inputs: 2 0–10 VDC analog inputs with 10-bit A/D resolution. They can be used to monitor compatible pressure, level, position, temperature-transmitter and other process signals.

A 4–20 mA transmitter should not be treated as a direct current input. The current signal must first be converted to a suitable voltage within the permitted 0–10 V input range using an appropriate resistor or signal converter.

Analog output: Not available.

Relay outputs: 10 digital relay outputs, rated up to 250 VAC / 2 A for resistive loads. These outputs are suitable for switching compatible contactors, signalling devices and other control loads within the specified contact ratings.

PTC temperature input: One dedicated input is provided for a 2-wire PTC temperature sensor, with an operating range of approximately -50 to +150 °C. The PTC input is separate from the two 0–10 V analog channels.

Battery-backed real-time clock

This version includes a battery-backed real-time clock, allowing control functions to operate according to actual date and time. Weekly and annual schedules can be created for pumps, ventilation systems, lighting, process equipment and other machinery that must operate at predefined times.

For applications that do not require calendar-based scheduling, see the Gemo AR2-A-24VDC-12D2A version without RTC.

Ladder programming and internal functions

The AR2 series is programmed with GEMO Ladder Editor. The ladder workspace provides 256 program lines, 5 contact columns and 1 output column. Rising-edge and falling-edge functions can be assigned to contacts where required.

Programs are transferred through the controller's RS-232 programming interface.

Available logic resources include 32 timers, 32 16-bit up/down counters, 32 offset counter comparators and 16 hysteresis analog comparators.

The analog comparator functions allow measured values to be evaluated against defined thresholds, making the controller suitable for level monitoring, pressure detection, alarm functions and basic analog process decisions.

Ladder scan time: Up to 10 ms.

Timer resolution: Minimum timing resolution is approximately 10 ms. Timer accuracy is specified as ±0.1% or 1 digit, whichever is greater.

High-speed counter inputs: Minimum ON and OFF times are approximately 1.25 ms. These inputs are intended for faster pulse counting and should not be confused with high-speed motion-control outputs.

Servo and step motor control

The relay-output AR2-A-24VDC-12D2A-RTC does not provide a high-speed pulse / direction output for positioning servo or step motor systems.

Applications requiring pulse-train positioning should use a PLC or motion controller designed specifically for high-speed motion control.

PID control

The presence of analog inputs does not mean that the controller includes a built-in PID loop. A dedicated PID algorithm is not provided.

Closed-loop temperature, pressure, flow or similar process-control applications requiring PID regulation should use a suitable process controller or a PLC with integrated PID functionality.

Display and operator functions

The controller features a 2 × 16 character backlit LCD display, three programmable front-panel function keys and a three-level password-protected menu system. User screens can be configured to show analog measurements, digital status, timing information, machine conditions and operator messages.

Can an external HMI be connected? Yes. A compatible operator panel / HMI can be integrated using the appropriate communication hardware.

For Modbus RTU communication, the appropriate AR2-S-24VDC-MB1 communication gateway and compatible controller software are required. The RS-485 expansion interface should not automatically be treated as a standard direct Modbus HMI port.

I/O expansion and RS-485

Compatible AR2 expansion modules can be connected through the controller's RS-485 expansion interface. The final number and type of available inputs and outputs depend on the selected expansion module and base-controller configuration.

RS-485 cabling: Use twisted, shielded, 2-core 24 AWG communication cable. Wiring polarity, shielding and line termination should follow the manufacturer's installation instructions.

Operating environment

Operating temperature: 0 to 50 °C.

Protection rating: IP20 according to EN 60529.

Relative humidity: Up to 80% at 30 °C, decreasing linearly to approximately 50% at 50 °C, non-condensing.

Terminal tightening torque: Maximum 0.5 N·m.

EMC and panel layout: EN 61000-6-1 and EN 61000-6-3 requirements should be considered during panel design. When the controller is installed alongside AC motor drives, frequency inverters, contactors or other sources of electrical noise, analog-signal, communication and power wiring should be physically separated where practical.

Particular attention should be given to the 0–10 V signal wiring. Proper shielding, grounding and separation from motor and inverter cables will help maintain stable analog measurements.

Gemo AR2 programming software and documentation

Download GEMO Ladder Editor V2.4 programming software for AR2 programming and configuration.

For detailed programming instructions, analog-input functions, timer and counter settings and RTC configuration, refer to the Gemo AR2 PLC English user manual.

For additional models and pricing, visit the Gemo price list, Gemo Electronic main page or our PLC product group.

For technical information and product selection, use our Gemo contact page or contact us at gemo@otomasyonavm.com.

Installation notice: Installation, wiring and commissioning of the Gemo AR2 should be carried out only by qualified technical personnel. Disconnect all power sources before working on the control panel. Particular care should be taken with analog, communication and power wiring to ensure reliable operation and compliance with the manufacturer's installation requirements.