Introduction to the Selec MIBRX Family of Low-Cost PLCs

This article is an introduction to the Selec MIBRX 2-slot PLC (Programmable Logic Controller), its associated expansion modules and how to assemble the components. In future articles I will be using the Selec MIBRX 2-slot PLC and its expansion modules to create different programs that simulate real world applications.

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Introduction to the Selec MIBRX Family

The Selec MIBRX family of PLCs has many different configurations to fit your needs as shown in Figure 1. This included a variety of DIN rail-mounted and panel-mount PLCs. Both DIN rail and panel-mount PLCs use the same expansion modules, and the expansion modules are interchangeable within the entire Selec MIBRX family of PLCs. The Selec expansion modules cards cover a range of different types of inputs and outputs that can be used to match your needs.

The PLC are categorized by the mounting provisions. The devices in the left are panel mount while the devices on the right are DIN rail mounted.

Selec MIBRX PLCs DIN Rail-Mount

The MIBRX DIN rail-mounted PLCs also come in three different sizes: MIBRX-2M, MIBRX-4M, and MIBRX-6M, which refer to the number of expansion modules each PLC can take. For example, the MIBRX-2M can accept 2 expansion module cards whereas the MIBRX-6M can accept 6 expansion module cards. The DIN rail-mounted PLCs also have built-in IO pins, with the number of IO pins depending on the unit’s size. There is also a space on the PLCs to mount an HMI or an adaptor for a cable to use a remote HMI. The DIN rail-mount PLCs come in both AC voltage and DC voltage models, so you will have to make sure you are selecting the appropriate model for your application.

Tech Note: The MIBRX-6M is the only model of the MIBRX series that uses screw terminals instead of spring terminals.

Selec MIBRX PLCs Panel-Mount

The MIBRX panel-mount PLCs come in three different panel sizes: MIBRX-48x96, MIBRX-72x72, and MIBRX-96x96, with each PLC containing a space for an HMI display. The panel-mount PLCs come with some Input/Output (IO) pins, depending on the size of the device. The MIBRX-48x96 and MIBRX-72x72 panel-mount PLCs both have two expansion slots, whereas the MIBRX-96x96 has six expansion slots. The panel-mount PLCs come in both AC voltage and DC voltage models, so you will have to make sure you are selecting the model that you need for your application.

Examples of Selec MIBRX Expansion cards

The Selec MIBRX Expansion cards.

The Selec MIBRX family is easily customizable with different expansion cards that can be used for input, output, and other functions for the PLC. There are expansion cards that add more digital inputs and analog inputs to your PLC. The analog input cards have some cards that use just a voltage input or current input, there are expansion cards that do read both voltage inputs and current inputs on a single card. The output cards offer a variety of outputs, including digital output cards with relay outputs or transistor outputs, as well as analog output cards in both voltage outputs and current outputs. There are also specialty cards available, such as a datalogging card, a Wi-Fi card, and a portable download card, to name a few.

Different Style Selec HMIs

Selec HMIs

The Selec HMIs will come with different variations depending on what model of PLC you are using. Each HMI will come with at least one button and a 7-segment or a graphical display. There are some HMIs that have buttons on them that the user can program how every they want to for their program. Unlike the expansion module cards not all HMIs are interchangeable since there are many that can only be used with certain models of PLCs. There is an option with the DIN rail-mounted PLCs to use a remote panel mount display so that you don’t have to have the PLC exposed to harsh environments.

Description of Parts Used

The parts mentioned in this article will be utilized throughout a series of articles demonstrating various PLC programs using the Selec PLC and the Selec Selpro software. These articles will illustrate practical examples using the Selec PLC and its expansion cards.


The Selec MIBRX-2M-1-0-0-24VDC is featured in this article. It is a 24-volt DC DIN-mount PLC. The foundation MIBRX-2M-1-0-0-24VDC PLC is just the base that all the parts mount to but, it does come with three digital inputs (DI0-2), inputs for the RS485 communication line, a temperature sensor (1FI), and connections for your DC power. While the PLC is listed as 24-volt DC, it is rated to work with 18 volts DC to 30 volts DC with a max power rating of 4 watts. When you first get the base unit, it will come with two covers for the expansion slots and a space to mount an HMI (Human-Machine Interface).


The HMI that I am using for this article is the MIBRX-DSP-2M-7-1-04-A, which has a 4-digit, 7-segment LED display and three keys, two of which can be configured by the user. The HMIs for the MIBRX DIN rail series are mounted to the center of the PLC by snapping them into place. There is also an option to use a remote HMI by connecting a plate to the HMI slot and using an RJ25 cable to connect the Selec MIBRX PLC to the remote HMI screen. The HMI is programmed using the Selpro software by selecting the HMI button in Selpro, which will automatically show the screen you selected when setting up a project in Selpro.

Tech Note: The HMI is sold separately

Module 1

The module in Slot 1 is the MIBRX-SC-RO04, which is a relay module with four Normally Open (NO) outputs that is rated for 5 Amps at 230 VAC or 30 VDC, with a response time of 20 milliseconds. The module is a NO relay that will close when activated by the PLC and uses a PNP output type. Since the module uses relays as its output type, the connections can be set up in a sourcing or sinking configuration. A sourcing configuration is created by connecting the common connections (C0 and C1) on the module to the positive side of the power supply, the relay outputs (R0–R4) are connected to the load, and the load is connected to the negative side of the power supply. A sinking configuration is created by connecting the common connections (C0 and C1) on the module to the negative side of the power supply, the relay outputs (R0–R4) are connected to the load, and the load is connected to the positive side of the power supply.

Module 2

The module in Slot 2 is MIBRX-SC-DI06, a six-input digital module that operates on 0 VDC to 30 VDC and can detect 7 VDC to 30 VDC. The digital input module card is rated for 5.5 mA at 24 VDC and uses a PNP-type input Applications of Type PNP and NPN Sensors. The input module uses a sinking configuration since it is a PNP-type input and is connected the same as the sinking configuration. To create that circuit, you connect the positive side of the power supply to the input device, the input device is then connected to the PLC’s digital inputs (D0–D5), and since this PLC does not have a common connection, the final connection is made internally within the PLC.

How to assemble the Selec MIBRX 2-slot PLC

After gathering all your parts (Figure 1), remove the covers on slots 1 and 2. You will need a flat-head screwdriver to push down on the locks while pulling the covers off.

Figure 1

Figure 1: Parts before assembly, the PLC base, HMI screen, a digital input module, and a relay output module.

Fit the expansion modules into the grooves on each side of the case so that they line up with the receptacle on the circuit board (Figure 2). When aligned, push the expansion module in until the locking tab is secured in place, ensuring the header pins mate into the header.

Figure 2: partly assembled PLC looking down on to the guide rails that the modules slide into.

After placing both expansion modules, position your HMI on top of the PLC with the bottom of the screen facing slot 1. You will need to push down evenly on all sides of the screen so that the header pins line up with the connector in the PLC. You will know the HMI screen is correctly positioned when both ends are locked in place with their locking clips.

Tech Note: There are no guide rails for the HMI, unlike the expansion modules, so be careful when placing the HMI.

You will know the PLC is assembled correctly when all the locking tabs are in place for the expansion modules and the HMI. The assembled PLC will look like Figure 3, with the expansion modules locked into the PLC and the bottom of the HMI aligned with slot 1. With the PLC assembled, you can then connect it to a DC power supply and a computer for programing the PLC.

Figure 3

Figure 3: Fully assembled PLC with all parts attached.

Tech Note: Ensure that when connecting the PLC, you correctly connect the wires. Connecting the power supply to the R485 +/- terminals will cause irreparable damage as the magic smoke is released.


In this article I covered the assembly process of Selec MIBRX PLC, important information about the PLC and its expansion cards. In future articles I will be using the Selec MIBRX PLCSTo cover the basics of Selec Selpro software, some ladder logic variables and gates, as well as how to program the Selec MIBRX PLCS using ladder logic. Feel free to leave any questions or feedback in this article

About this author

Anthony Fish is a passionate and skilled technician with five years of experience in the electronics industry. He graduated from Northland Community & Technical College with a degree in electronics technology and automation systems. Fish is currently working as an electronics technician at DigiKey, with a focus on automated and industrial control systems. He enjoys the challenge of answering your technical question via phone, chat, or this forum.

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