GEMO AR2-A Series – DIN-Rail Smart Relay / Compact PLC Family

The GEMO AR2-A series is a family of DIN-rail programmable controllers developed for compact machine automation, control panels, sequencing, timing, counting and simple process-control tasks. Different versions are available with 24 VDC or AC mains supply, relay or transistor outputs, optional analog inputs and optional real-time clock, allowing the controller to be selected around the actual application rather than forcing every feature into one model.

Developed by GEMO Elektronik in Türkiye, the AR2-A platform combines conventional ladder programming with a built-in LCD and front-panel controls. It is particularly useful where a compact programmable controller is needed without the size and complexity of a larger PLC system.

Choose the AR2-A model by application, not only by I/O count

AR2-A controllers are offered with different supply and I/O combinations. Depending on the model, the supply may be 18–32 VDC or 100–240 VAC. Digital-input quantity, output type, analog capability and real-time clock availability also vary by model code.

Not every AR2-A feature is available on every version. In particular, the compact 8D models have fixed I/O and are not expandable, while larger AR2-A versions can work with compatible expansion modules.

Ladder programming with GEMO Ladder Editor

AR2-A applications are created with GEMO Ladder Editor. The programming area provides 256 ladder lines, 5 contact columns and 1 output column. Rising-edge and falling-edge functions can be assigned to contacts, making event-driven logic easier to implement.

The software supports program creation, simulation and program transfer. Password protection can also be used to restrict access to an application.

Typical ladder scan time is below approximately 10 ms, depending on program size and structure.

Timers, counters and internal logic resources

The AR2-A platform includes 32 timers with multiple operating modes and time ranges, together with 32 16-bit up/down counters and 32 offset counter comparators.

Additional programming resources include high-speed counter functions, auxiliary relays, edge-triggered contacts and state-machine functions. These features allow the AR2-A to handle considerably more structured control logic than a conventional electromechanical smart relay.

Digital I/O and expansion capability

The physical number of digital inputs and outputs depends on the selected AR2-A controller. On compatible expandable models, the complete system can reach approximately 28 digital inputs and 20 digital outputs when the appropriate expansion hardware is added.

These figures describe the maximum system capacity of compatible controller and expansion combinations; they are not the onboard I/O count of every AR2-A model.

The smaller AR2-A-8D versions are fixed-I/O controllers and must be selected around their onboard input and output capacity.

Analog measurement on selected models

Some AR2-A versions include 0–10 V analog inputs for signals such as pressure, level, position or other process measurements.

On compatible expandable configurations, the system can provide up to 4 analog input channels. Models without physical analog inputs cannot obtain analog measurement capability simply through ladder software functions.

The programming environment also includes 16 hysteresis analog comparators, allowing measured values to be evaluated against adjustable thresholds for alarm, switching and simple process decisions.

PTC temperature-sensor support

Selected AR2-A controllers provide a dedicated input for a compatible PTC temperature sensor. Temperature status can therefore be incorporated directly into the ladder sequence without using one of the general-purpose digital inputs.

Compatible expandable configurations can provide an additional PTC channel through the appropriate module. A dedicated PTC input is separate from a standard 0–10 V analog channel.

RTC versions for calendar-based control

AR2-A models carrying the RTC suffix include a battery-backed real-time clock. These versions can execute control logic according to actual date and time, making them suitable for weekly and annual schedules.

A standard ladder timer measures elapsed time only. Applications that must start or stop equipment according to the day of the week, calendar date or actual clock time should therefore use an RTC-equipped AR2-A model.

Built-in LCD and operator interface

AR2-A controllers feature a 2 × 16 character backlit LCD together with three programmable front-panel function keys. Machine status, timer and counter values, process information and operator messages can be displayed without adding a separate panel meter or basic text display.

The controller software provides multiple user-display pages and a three-level password-protected menu system, allowing basic operator settings and machine information to remain inside the controller.

External HMI and Modbus options

Compatible larger AR2-A controllers can be integrated with an external operator panel / HMI using the appropriate communication hardware and software configuration.

For Modbus RTU applications, compatible AR2-A models require the appropriate GEMO communication gateway. The compact AR2-A-8D family is outside this Modbus gateway arrangement.

Applications requiring an external touchscreen, network communication and extensive I/O should therefore be designed around one of the expandable AR2-A versions rather than an 8D controller.

AR2-A is a general-purpose controller, not a motion PLC

Standard AR2-A controllers do not provide the high-speed pulse / direction output required for positioning servo or step motor systems. Applications involving pulse-train motion control should use a suitable motion PLC or dedicated controller.

Likewise, the AR2-A family does not provide a ready-made built-in PID loop for closed-loop pressure, flow or temperature regulation. Applications requiring PID control should use a suitable process controller or PLC with PID capability.

Installation in industrial control panels

AR2-A controllers can be installed in panels that also contain motor drives, contactors and other industrial equipment, but correct panel design remains essential. Control, communication and analog wiring should be separated from motor and power cables wherever practical.

Correct grounding, shielding and cable routing are particularly important when analog measurement or communication is used in a panel containing frequency inverters or other electrical-noise sources.

Programming software, manuals and support

AR2-A controllers can be programmed with GEMO Ladder Editor V2.4.

For detailed ladder instructions, timers, counters, display functions and controller configuration, refer to the GEMO AR2 PLC English user manual.

Additional application material is available in the Gemo PLC lessons and forum.

For model and commercial information, visit the Gemo PLC price list or the Gemo Electronic main page.

Software compatibility note: Older AR2 documentation contains different statements regarding program read-back and online monitoring / simulation. Where these functions are important, compatibility should be checked against the controller firmware and GEMO Ladder Editor version actually in use.