Gemo AR2-A-230VAC-12D2A-RTC – Expandable Smart Relay / PLC with Analog Inputs, Relay Outputs and Real-Time Clock

Gemo AR2-A-230VAC-12D2A-RTC is an expandable smart relay / PLC designed for machine automation, control panels and applications that combine digital logic with analog measurement and calendar-based control. The controller operates directly from an AC mains supply and provides 12 digital inputs, 2 analog inputs, 10 relay outputs, a dedicated PTC temperature-sensor input and a battery-backed real-time clock.

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

Power supply and I/O configuration

Power supply: 100–240 VAC, 50/60 Hz. Although the model designation includes 230VAC, the controller is designed for a wide AC mains input range. Maximum power consumption is approximately 6 W.

Digital inputs: 12 low-voltage DC digital inputs are provided. The controller itself is powered from the AC mains, but the digital-input terminals must not be treated as 230 VAC inputs.

Auxiliary DC supply: The AC-powered AR2 provides an internal 18 VDC auxiliary supply for use with its digital-input circuitry.

Digital input filter: Standard 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. These channels can be used with compatible pressure, level, position and other process transmitters that provide a voltage output within the permitted range.

The controller does not provide dedicated 4–20 mA current-input terminals. A 4–20 mA transmitter must therefore be converted to an appropriate voltage within the 0–10 V input range using a suitable resistor or signal converter.

Analog output: Not available.

Relay outputs: 10 digital relay outputs, rated up to 250 VAC / 2 A for resistive loads. Suitable suppression or interface components should be considered when switching inductive loads such as contactor coils, solenoid valves or similar devices.

PTC temperature input: One dedicated input is provided for a 2-wire PTC temperature sensor, covering approximately -50 to +150 °C. The PTC channel is independent of the two 0–10 V analog inputs.

Battery-backed real-time clock

The AR2-A-230VAC-12D2A-RTC includes a battery-backed real-time clock, allowing control sequences to operate according to actual date and time rather than only elapsed timer values.

Weekly and annual schedules can be created for pumps, ventilation systems, lighting, heating equipment and machinery that must operate at predefined times.

For applications that do not require calendar-based scheduling, see the Gemo AR2-A-230VAC-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 programmable thresholds. This makes the controller useful for level monitoring, pressure detection, alarm generation and simple analog process decisions without requiring a separate analog controller.

Ladder scan time: Approximately 10 ms or less, depending on the application program.

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: Fast-counter functions are available for pulse-counting applications. These inputs are intended for counting and should not be confused with high-speed positioning outputs.

Servo and step motor control

The relay-output AR2-A-230VAC-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 specifically designed for high-speed motion control.

PID control

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

Closed-loop temperature, pressure, flow or similar process-control applications 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. Digital status, analog measurements, timer values, counter values, RTC information and operator messages can be displayed directly on the unit.

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 I/O capacity depends on the selected expansion module and the base-controller configuration.

RS-485 cabling: Use twisted, shielded, 2-core 24 AWG communication cable. A-to-A and B-to-B polarity should be maintained, and 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 as temperature rises to approximately 50% at 50 °C, non-condensing.

Installation altitude: Below approximately 2000 m above sea level.

Terminal tightening torque: Maximum 0.5 N·m.

EMC and panel layout: When the controller is installed in the same enclosure as AC motor drives, frequency inverters, contactors or other sources of electrical noise, analog-signal, communication and power wiring should be physically separated wherever practical.

Particular attention should be given to the 0–10 V analog wiring. Correct shielding, grounding and separation from motor and inverter cables will help maintain stable measurements. AC mains wiring should also be kept physically separate from low-voltage control and communication circuits.

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, timers, counters 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 the AC supply before wiring or servicing the controller. Suitable isolation and overcurrent protection should be provided, and mains, analog-signal and low-voltage control wiring should be installed in accordance with the manufacturer's instructions and applicable electrical-safety requirements.