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Visual Cue
Slide 1:

Welcome Slide

Welcome to the spoken tutorial on OpenPLC Main board.
Slide 2:

Learning Objectives

  • Various Components on OpenPLC Main board
In this tutorial, we will learn about
  • Various components of OpenPLC Main board
Slide 3:

System Requirements

  • OpenPLC Main board
  • 24V, 2A SMPS
  • USBasp programmer
  • Ubuntu Linux 18.04 operating system
To record this tutorial I am using:
  • OpenPLC Main board
  • 24V, 2A SMPS
  • USBasp programmer
  • Ubuntu Linux 18.04 operating system
Slide 4:

OpenPLC hardware

  • Affordable, open source and modular hardware
  • Flexible and can be interfaced with any electronic module
  • OpenPLC is an affordable, open source & modular hardware developed at IIT Bombay by FOSSEE team.
  • This board is flexible and can be interfaced with any electronic module available in the market.
Development-board.png This is a picture of OpenPLC Main board.
power-unit.png This highlighted section is the power unit of the board.

It is further subdivided into input and output power sections.

Input Power Section:


We will now take a look at the input power section of the board.

The board must be powered using 24 volt DC power supply.

The 24 volt and 12 volt connections are capable of handling upto 2 amperes of current.

Highlight input power screw terminals


The on board 24V input power terminals are shown on your screen marked GND which is ground, and 24V.
SMPS.jpg We are using a 24V, 2A SMPS for power supply.
Highlight L, N, GND


We have to connect line, neutral and ground terminals of 3-pin AC power cord to SMPS.

Make sure that you identify the terminals of 3-pin AC power cord correctly.

Highlight -V, +V


Connect the +V and -V ends of the SMPS to 24V and GND of the main board as shown here.
wrong-connection.jpg While making connections, make sure that exposed metal from the wire is not protruding out.
wrong-connection.jpg This is a wrong way to connect a wire.
wrong-connection.jpg We should not connect the wires in this fashion as this may cause electrical shorts later on.
correct-connection.jpg This is a right way to connect a wire.

Tighten the screws properly.

Tug the wire moderately to ensure that they are secured in place.

After making all the connections properly, turn on the power supply.
D2-glow.jpg Make sure that the D2 LED is glowing on your board which indicates that the board is powered up.
Output power section:

<output-power-pins.png with labels>

We will now take a look at the output power section.

24, 12, 5 V and Ground outputs are provided for connections with external modules.

The connections are provided through 4 different types of connectors. They are:

  • Relimate
  • Male berg strip
  • Female berg strip
  • Screw terminal
Highlight relimate connectors


There are 4 relimate connectors on the board as marked in the picture.

Most of the modules developed by FOSSEE will be compatible with these connectors.

Highlight relimate connectors


These will be easier to access with multi strand cables, if you do not have single strand cables.
Highlight female and male connectors


Some external modules in the market are available with either male or female berg connections.

In order to accommodate both types of modules, we have male as well as female connectors.

Highlight microcontroller


At the heart of the main board is ATMega16 microcontroller.
The microcontroller has 4 ports namely PORTA, PORTB, PORTC and PORTD.

These ports may be configured to use as a digital input or digital output as desired.

portA.png Port A can be accessed from pin 0 to 7 through this section as labelled.

Port A can also be configured as analog inputs.

Highlight 4 pins beside port A


The 4 pins marked doesn’t belong to Port A.

They are output power pins as described before.

portB.png Port B can be accessed from pin 0 to 7 through this section as labelled.
portC.png Similarly, PORT C
portD.png And PORT D
Highlight female, male berg connectors and screw terminals(separately)


We can connect external inputs or outputs to the board in either of the 3 ways:
  • Female berg connectors or
  • Male berg connectors
  • Screw terminals.
reset.png We can reset the program in the microcontroller using the RESET button.

Pressing the RESET button will only reset the state of program variables.

It will not erase the program from the microcontroller.

ISP-header.png This is a standard ISP header to program the microcontroller.

We can connect an external programmer to this header and program the controller.



To connect the header, simply match the notch on the ISP cable with the groove in the header as shown.

The programmer shown in this tutorial is an USBasp programmer.


(Highlight UART pins with red box)

Highlight status LEDs

The UART pins along with 5V and GND are provided to attach an external UART module.

The pin arrangements are shown in the picture.

There are two status LEDs near the header to notify communication status.

Slide 5:

Points to remember:

  • Most of the modules developed by FOSSEE run on 12 volts
  • 24 volt connection is also provided

Points to remember:
  • Almost all the modules developed by FOSSEE are designed to work with 12 volts.
  • But since most PLC modules operate on 24 volts, we are providing an option to access 24V on board.
This brings us to the end of this tutorial.

Let us summarize.

Slide 6:


In this tutorial, we learnt about

  • Various components on OpenPLC Main board

In this tutorial, we learnt about

  • Various components of OpenPLC Main board
Slide 7:

About Spoken Tutorial project

The video at the following link summarises the Spoken Tutorial project.

Please download and watch it

Slide 8:

Spoken Tutorial workshops

The Spoken Tutorial Project team:
  • conducts workshops using spoken tutorials and
  • gives certificates on passing online tests.

For more details, please write to us

Slide 9:

Forum questions:

Please post your timed queries in this forum.
Slide 10:

Forum for specific questions:

Do you have any general / technical questions on OpenPLC?

Please visit the FOSSEE forum and post your question.

Slide 11:


Spoken Tutorial Project is funded by MHRD, Government of India.
Slide 12:

Thank you slide

This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay.

And this is Harsha Priyanka from FOSSEE team, signing off.

Thanks for watching.

Contributors and Content Editors

Nancyvarkey, Nirmala Venkat, Priyanka.guntaka123