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PR103 Ethernet-Enabled Mini-PLC

SKU: PR103
PR103 is a Mini-PLC with extended communication capabilities and a total of 26 built-in digital and analog I/Os designed to implement basic control systems for various applications such as lighting control, pumping control, ventilation and heating control, and others.

6 digital inputs4 fast digital inputs8 digital outputs6 analog inputs2 analog outputsModbus RTU/ASCII/TCPRS485 interfaceEthernetUSB interfacebuilt-in real-time clockDIN rail mountingsoftware at no chargeAmbient temperature

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Product Description

    PR103 is a Mini-PLC with extended communication capabilities thanks to its Ethernet port and two RS485 interfaces as well as both Modbus TCP and Modbus RTU/ASCII protocols. While communicating via Modbus RTU/ASCII over the RS485 interfaces on the field/control level, PR103 can use the Ethernet port and Modbus TCP to ‘bridge’ data to the supervisory level of the automation pyramid.

    The PR103 Mini-PLC is equipped with 10 digital inputs, 8 digital outputs, 6 analog inputs, and 2 analog outputs. Moreover, 4 of 10 digital inputs can be used as pulse counters processing signals from 100-kHz encoders. Concerning the analog inputs, they are configurable and can operate with a wide range of RTDs, NTC/PTC, as well as with standard linear signals of 4-20 mA or 0-10 V. Furthermore, the built-in I/Os may be directly expanded with up to two extension modules of the PRM series.

    Thanks to built-in flash memory, the logging of, e.g. values on analog inputs/outputs, pulse counters, device status, etc., is possible. The file is stored in the CSV format, which allows its running in almost any spreadsheet editor, for example, Excel.

    Designed for installation on a DIN rail in a control cabinet, PR103 can operate in non-heated environments down to -40°C as well as in heated ones in temperatures up to +55°C.

    A user program is written in function block diagram language in the akYtec ALP programming software, which is available free of charge. The control algorithm is loaded into the device memory via a micro USB cable connection.

    Functions and features
    • Ethernet port (Modbus TCP, Client/Server)
    • 2x RS485 interfaces (Modbus RTU/ASCII, Master/Slave)
    • 10 digital inputs, 4 of which support pulse counting (up to 100 kHz)
    • 6 analog inputs, each capable of connecting:
      • RTD sensors (Pt500/1000, Ni500/1000, etc.)
      • NTC/PTC sensors
      • 4-20 mA / 0-10 V signals
      • Digital signals
    • 2 analog outputs configurable for 4-20 mA or 0-10 V
    • PRM-expandable: up to 32 additional I/O points over an internal bus with no loss in performance
    • Extended operation temperature range: -40...+55 ºС
    • USB-powered in the programming mode
    • Software-based features include: retain variables, day timer, week timer, PID control, etc.
    • Real-time clock
    • Logging function
    Enclosure design features
    • Thanks to its MCB-like form, the device enclosure fits perfectly fit into almost any consumer unit not to mention control cabinets
    • Removable terminal blocks
    • Convenient battery replacement


    PR103.24.2.3 24 V DC, 10DI + 8DO + 6AI + 2AO, 2x RS485 (Modbus RTU/ASCII), Ethernet (Modbus TCP)
    Power supply 24 (9...30) V DC
    Power consumption, max. 10 W
    Real Time Clock Backup 5 years (CR2032)
    Real Time Clock accuracy ± 3 s/day
    Extension modules up to 2 PRMs
    Dataset size, max. 2 kB
    Logging cycle, min. 30 sec
    File type *.CSV
    Configuration software akYtec Tool Pro
    Programming environment akYtec ALP
    Programming language FBD
    Programming interface Mini-USB, Ethernet
    Memory ROM 128 kB
    RAM 32 kB
    Retain memory 1016 Byte
    Interfaces 2x RS485, Ethernet
    Protocols Modbus TCP (Slave)
    Baud rate 10/100 MBit/s
    Galvanic isolation 510 W
    Quantity 2
    Protocols Modbus RTU / ASCII (Master / Slave)
    Baud rate 9.6...115.2 KBit/s
    Galvanic isolation 1500 W
    Digital inputs
    Quantity 6
    Type Switch contact
    Logical states 1 8.5...30 V DC (2...5 mA)
    0 -3...+5 V DC (0...15 mA)
    Galvanic isolation in groups of 2 and 4
    Fast digital inputs
    Quantity 4
    Logical states 1 8.5...30 V DC (2...5 mA)
    0 -3...+5 V DC (0...15 mA)
    Pulse width, min. 5 mks
    Pulse frequency, max. 100 kHz
    Galvanic isolation in group of 4
    Universal inputs
    Quantity 6
    Input signal Analog / Digital
    Galvanic isolation none
    Analog input 4-20 mA, 0-10 V, 0-300 kOhm
    Pt1000, PTC, NTC
    (the complete list)
    ADC resolution 12 bit
    Digital outputs
    Quantity 8
    Type relay, NO
    Galvanic isolation individual
    Switching capacity AC 5 A, 250 V (resistive load)
    DC 3 A, 30 V
    Minimum load current 10 mA (at 5 V DC)
    Analog outputs
    Quantity 2
    Analog outputs 4-20 mA, 0-10 V
    Permissible load 15...30 V
    DAC resolution 12 bit
    Galvanic isolation individual
    Ambient temperature -40...+55 °C
    Storage temperature -25...+55 °C
    Humidity up to 80 % (at +25 °C, non-condencing)
    IP Code IP20
    Dimensions 123 × 108 × 58 mm
    Weight approx. 350 g
    Material plastic
    Sensor Measuring range 
    RTD according to IEC 60751:2008
    Pt500, Pt1000 -200…+850°C
    Cu500, Cu1000 -50…+200°C
    Ni500, Ni1000 -60…+180°C
    RTD according to GOST 6651
    500P, 1000P -200…+850°C
    500M, 1000M -50…+200°C
    Thermistors / NTC
    B57861S series, 2 kΩ, B25/100 = 3560 -55…+100°C
    B57861S series, 3 kΩ, B25/100 = 3988 -55…+145°C
    B57861S series, 5 kΩ, B25/100 = 3988 -35…+145°C
    B57861S series, 10 kΩ, B25/100 = 3988 -35…+155°C
    B57861S series, 30 kΩ, B25/100 = 3964 -20…+155°C
    B57861S series, 50 kΩ, B25/100 = 3760 -10…+155°C
    NTC 3435, 10 kΩ -40…+105°C
    NTC 3977, 10 kΩ -40…+125°C
    Thermistors / PTC
    KTY82-110 -55…+150°C
    Standart signals
    0-10 V
    4-20 mA
    Resistive signal
    0-300 kOhm 0...100%


    Time Delay of RS485 datastream and analog output?

    The program execution time (cycle time) is automatically adjusted based on the program complexity (Auto-Tuning). The automatic adjustment affects the data exchange via Modbus since program execution takes higher priority over processing requests. If the program is very extensive, it can consume the entire CPU time, and the Modbus data exchange will not be carried out correctly.

    To avoid this issue, a lower limit is reserved for the volume of Modbus data exchange: 50 requests per second. This means that at least 50 requests per second can be executed, even if the user program is large, and even more if the program is small and the processor performance is sufficient. If there is not enough time to query all devices, the number of queries in the user program should be optimized.

    The setting of the polling cycle depends on the number of variables queried and the polling frequency in the program. It is recommended to set the polling cycle to 1 second. In this case, the device can query up to 50 variables.

    The minimum processing time of the program cycle is 1ms, and the signal conversion time for analog outputs is 100ms.

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    Difference between PNP and Relais Output?

    The PR’s has relais outputs, Relay outputs use an electromagnetic coil to actuate a switching contact. When the control voltage is applied to the relay coil, it either closes or opens the switching contacts to control the load.

    Whereas PNP transistor outputs are commonly used in control circuits to switch electrical loads, such as relays, LEDs, or motors.

    They are e used to provide a positive voltage signal to turn on or control a connected load. When a positive voltage is applied to the base, the transistor becomes conductive, and the collector is connected to the emitter, allowing current to flow to the load.

    The main difference is that PNP transistor outputs represent an electronic method for controlling loads, while relay outputs are electromechanical devices. The choice between them depends on the specific requirements of the application and design preferences.

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    What is the maximum load capacity of the inputs and outputs?

    Digital Input: 264 V AC (for 230.x.x Version) 30VDC (for 24.x.x version)

    Digital Output: AC 5A, 250 V DC: 3A, 30V

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    Can I use the PR devices to control and monitor the current of my PV system?

    Yes, the PR-devices series can be used to monitor and control the consumption of a PV system. The PR series supports the Modbus RTU protocol, making it compatible with any energy meter that supports this protocol. The digital outputs of the series are suitable for control purposes and can, for example, redirect the current to a battery, the general power grid, or heating elements

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    Loss of data. Do you lose the ALP program when you change the battery?
    The user program is written to the retain memory. The battery can be changed without any issues, and the program remains unaffected. It's worth noting that when the battery is replaced, the RTC will be reset. The battery typically lasts for about 8 years.
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    Compatibility with HMI? What does a HMI need to be working with the PR-devices?
    Any HMI device compatible with the Modbus RTU Protocol is of displaying process values and can be utilized as an HMI with the PR device series.
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    What happens to my variables when we have a power failure? Is the program persistent?
    The program is stored in the retain memory, which remains unaffected in the event of a power failure. Therefore, in the event of a power failure, your PR device will retain the program and will not require reprogramming. Variables that must be stored in non-volatile memory must be marked as retain in the ALP project.
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    Can the PR-Devices be used as a PID-Controller?
    Yes the PR-devices can function as PID-Controller, our ALP Software utilizes function block language and comes with preinstalled macros like PID Controller and PWM Generator, among others.
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    Can I control a pumping System with the PR-devices?

    Yes, the PR-Devices can be used to control pumping systems. Therefore, we recommend exploring the sample projects available on our website. We also offer sample projects that showcase the capabilities of PR devices, such as a press machine.

    In one of these projects, we demonstrate how the programmable relay PR200 can be utilized to enhance operator safety when operating a press machine. Additionally, a counting function has been implemented, and its results are displayed.

    Another example project involves a modifiable week clock. Some automation tasks require toggling secondary devices based on specific schedules, which can change over time. With this sample project you can learn how to set more importantly, modify the schedule of output activities using the PR’s function keys and screen.

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    What steps do I have to take to calibrate the PR-devices when i have uncertanties in the measurement?

    If the accuracy of the input or output of the module is no longer in accordance with the specification, it can be calibrated.

    Each analog input and output has its own calibration coefficients for each sensor type.

    – The calibration is performed using a reference signal source connected to the device input or output.

    – The calibration coefficients are calculated based of the ratio between the current input signal and the reference signal and stored in the non-volatile device memory.

    – If the calculated coefficients go beyond the permissible limits, a message about the error cause will be displayed.

    For further concrete instructions on page 36 in the manual shows step by step instructions on how to calibrate input/ or output

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    How does the Modbus register work and why is it in hexadecimal? (3x0000 to 3xFFFF)

    Modbus registers work as a way to store and exchange data in Modbus communication, which is a popular protocol used in industrial automation and control systems. Modbus registers are typically 16-bit values, and they are indeed represented in hexadecimal format. Here's an explanation of how Modbus registers work and why hexadecimal is used:

    1. Data Storage: Modbus registers are used to store various types of data, such as sensor readings, control parameters, status information, and more. These registers are organized in a range from 0x0000 to 0xFFFF, which covers 65,536 possible values.
    2. 16-Bit Format: Each Modbus register is 16 bits (2 bytes) in length. This means that it can hold values ranging from 0 to 65,535. The 16-bit format is common in industrial control systems because it provides a good balance between precision and data size.
    3. Hexadecimal Representation: Hexadecimal (base-16) is used to represent Modbus registers for several reasons:
      • Compactness: Hexadecimal allows for a compact representation of binary data. Each hexadecimal digit represents four binary bits, making it efficient for displaying and working with 16-bit values.
      • Human Readability: Hexadecimal is more human-readable than binary or decimal for 16-bit values. It uses the digits 0-9 and the letters A-F to represent values from 0 to 15.
      • Alignment: Hexadecimal values align neatly with bytes. In a Modbus register, each byte is represented by two hexadecimal digits, making it easier to work with when dealing with byte-oriented communication protocols.
      • Consistency: Hexadecimal is consistent with the way data is often displayed and configured in industrial control systems and related software.
    4. Addressing: The "3x" in "3x0000 - 3xFFFF" refers to the Modbus function codes. In Modbus, function codes 3 and 4 are used for reading and writing registers. The "x" in "3x" signifies that these registers are in the "holding registers" category. Holding registers are used to store data that can be read and written by external devices
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