PLCs and mini-PLCs are very similar in terms of function, hardware, operation, design, etc., which makes them quite replaceable and universal devices. The main distinguishing feature of these devices is the programming software. For this reason, the user has to be thoroughly familiar with the programming environment in order to be able to program the device. Sometimes it is a time-consuming activity. To save your time, we have decided to provide you with various sample projects on programming our programmable relay PR200. Our main goal is to build as many projects as necessary to encompass all the functionality of the akYtec ALP programming environment.

According to our technical support team, the processing of analog inputs and using of the RS485 interface are the most frequently asked questions about the PR200 and akYtec ALP. On this basis, we have decided to dedicate or first sample project to exactly this topic.

There are many ways to use analog inputs of a PLC in industrial automation, HVAC, or agriculture. One of the most common is the monitoring of temperature and humidity. For this purpose, akYtec GmbH offers the following devices:

  • - Temperature sensor DTS125L
  • - Temperature transmitters NPT1 and NPT3
  • - Humidity and temperature transmitters PVT10 and PVT100

For this sample project, we use two temperature sensors – DTS125L-PT100 and DTS125L-PT1000 – to monitor the temperature and display the settings of the configurable analog inputs (4-20 mA, 0-10 V or 0-4000 ohm). The PT1000 is connected directly. We simply use an analog input of the PR200 for 0…4000 ohm and utilize a ready-to-use macro 'Pt1000' from the Online Macro Database. One could do the same with the PT100 if no negative effect on the signal accuracy would occur. To solve the problem, we connect our PT100 sensor via the temperature transmitter NPT1. The NPT1 converts the signal of the sensor into the signal of 4-20 mA so that our programmable relay PR200 can evaluate it.

The Programmable Relay PR200 from akYtec is available in many variants, depending on the supply voltage, the number of the RS485 interfaces and I/O points. Since this project requires two RS485 interfaces and a 4-20 mA output, the PR200-24.2.2 fits best here. This programmable relay is powered by 24 V DC and features four analog inputs, two 4-20 mA analog outputs, and two RS485 interfaces.

The humidity and temperature transmitter PVT100 was selected for the humidity measurement. This device can be connected to an analog input or to an RS485 interface. We prefer the second option to guide you through the Modbus settings in the akYtec ALP. The second RS485 interface is used to output data from the PT100 temperature sensor and display them on the SMI2 RS485 Display. The humidity value is displayed on the ITP11 process display, which is connected to one of the analog outputs of our compact PLC.

The intelligent relay PR200 has a 2-line 32-character LCD display. In order to familiarize you with the programming of this display, we have brought the data of all connected sensors on the display.

programmable relay

The project file and its detailed description can be found on the product page of the PR200 programmable relay > Product description > Sample project.