Gemo AR2-A-24VDC-8D – Compact Smart Relay / PLC with 8 Digital Inputs and 5 Relay Outputs

The Gemo AR2-A-24VDC-8D is intended for compact control jobs where a full-size PLC would add unnecessary complexity. With 8 digital inputs, 5 relay outputs and a dedicated PTC temperature-sensor input, it covers many straightforward machine, panel and sequencing applications while retaining ladder-logic programming and a local LCD interface.

Typical uses include small machine interlocks, pump or fan sequences, timer-based operations, counter applications and simple panel automation. Gemo AR2 products have been available through our website since 2011.

24 VDC operation with fixed I/O

This version operates from 18–32 VDC. It is a DC-powered controller; references to AC/DC supply in older product text do not apply to this model.

Eight filtered digital inputs are available for conventional control signals from sensors, pushbuttons, limit switches and similar field devices. Standard input filtering is approximately 8 ms, helping reject short disturbances before they are interpreted by the ladder program.

The controller switches its outputs through 5 relay contacts. Each relay is rated up to 250 VAC / 2 A for resistive loads. Inductive devices such as contactor coils and solenoid valves should be provided with suitable suppression or interface protection.

No general-purpose analog input or analog output is fitted to the AR2-A-24VDC-8D. The dedicated PTC channel should therefore not be confused with a conventional 0–10 V analog input.

PTC temperature monitoring

A dedicated input is provided for a compatible PTC temperature sensor. Temperature status can be incorporated directly into the ladder sequence, making the controller useful for applications where a simple thermal condition must be monitored alongside digital machine logic.

No real-time clock on this version

The standard AR2-A-24VDC-8D does not include a battery-backed real-time clock. Its internal timers handle elapsed-time functions, but they do not provide calendar-based weekly or annual scheduling.

Where actual date and time are required, use the Gemo AR2-A-24VDC-8D-RTC version.

Ladder logic without a large PLC platform

Programming is carried out with GEMO Ladder Editor. The available ladder area consists of 256 program lines, 5 contact columns and 1 output column, with rising-edge and falling-edge functions available for contacts.

The application is transferred through the controller's RS-232 programming interface. Internal logic resources include 32 timers, 32 16-bit up/down counters, 32 offset counter comparators, 2 high-speed counters and 48 auxiliary relays.

The controller also supports status-machine and display functions that allow considerably more structured control logic than a conventional electromechanical smart relay.

Program scan time is below approximately 10 ms, depending on the application. Fast-counter functions are intended for pulse counting and should not be mistaken for high-speed motion outputs.

Not a motion controller

Because this version uses relay outputs, it does not provide high-speed pulse / direction outputs for positioning servo or step motor systems. Applications requiring pulse-train positioning need a PLC or motion controller designed specifically for that task.

PID control is not built in

The AR2-A-24VDC-8D does not include a dedicated PID control algorithm. Closed-loop temperature, pressure, flow or similar process regulation should be handled by a dedicated process controller or a suitable PLC with PID capability.

Local display and front-panel operation

A 2 × 16 character backlit LCD is built into the controller together with three programmable front-panel function keys. Machine status, timer values, counter information and operator messages can therefore be viewed without adding a separate display.

The software provides multiple user-display pages and a password-protected menu structure, allowing basic operator interaction to remain inside the controller itself.

Fixed architecture – no I/O expansion

The AR2-A-24VDC-8D is not expandable. The RS-485 I/O expansion arrangement used by larger AR2 models does not apply to the 8D family.

The application should therefore be designed around the available 8 inputs and 5 outputs. If additional I/O is likely to be required later, an expandable AR2 version should be selected from the beginning.

Modbus and external HMI limitation

The AR2-A-8D family is also excluded from the AR2-S-24VDC-MB1 Modbus RTU gateway support provided for larger AR2 controllers. Consequently, the standard AR2 Modbus gateway arrangement should not be specified for this model.

If an application requires a networked operator panel, Modbus RTU communication or more extensive I/O, a higher-level AR2 controller or another PLC / HMI platform is the more appropriate choice.

Panel installation

The controller is intended for operation between approximately 0 and 50 °C and has an IP20 protection rating. Condensation should be avoided and terminal screws should not be tightened beyond the manufacturer's specified torque.

When the AR2 is installed in the same cabinet as AC motor drives, frequency inverters, contactors or other electrical-noise sources, control wiring should be routed separately from motor and power cables wherever practical. Correct grounding and cable routing remain important even in a compact PLC installation.

Programming software and documentation

Use GEMO Ladder Editor V2.4 for programming, simulation and controller configuration.

Detailed information on ladder instructions, timers, counters, displays and controller functions is available in the Gemo AR2 PLC English user manual.

For other Gemo models and commercial information, visit the Gemo price list, the Gemo Electronic main page or our PLC product group.

For model selection and technical questions, use the Gemo contact page or contact us at gemo@otomasyonavm.com.

Installation notice: Wiring, commissioning and servicing should be carried out only by qualified technical personnel. Disconnect the power supply before working on the controller or panel and follow the manufacturer's installation requirements and applicable electrical-safety rules.