View source for OpenPLC-version1-with-LDmicro/C3/PWM-Instruction/English


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|-

| align=center| '''Visual Cue'''
| align=center| '''Narration'''
|- 
|| Slide 1: 
|| Welcome to the spoken tutorial on '''PWM Instruction'''
|- 
|| Slide 2: 

Learning Objectives
* PWM (Pulse Width Modulation) instruction

|| 

In this tutorial we’ll learn about working of '''Pulse Width Modulation''' instruction.
|- 
|| Slide 3: System Requirements
* Ubuntu 18.04 OS
* LDmicro
* OpenPLC V1 Mainboard
* 24V, 2A SMPS
* USBasp programmer
* Heater module

|| To record this tutorial I am using:
* '''Ubuntu Linux 18.04''' operating system
* '''LDmicro'''
* '''OpenPLC version 1 Mainboard'''
* '''24V, 2A SMPS'''
* '''USBasp programmer'''
* '''Heater module'''
|- 
|| Slide 4: Pre-requisites
* Heater module
* Working of '''Move''' instruction.

If not, please refer to the relevant tutorials from [https://spoken-tutorial.org/ Home | spoken-tutorial.org]
|| To follow this tutorial, you should know about
* '''Heater module''' and
* Working of '''Move''' instruction.

If not, please refer to the relevant tutorials in this series on this website.
|- 
|| Slide 5: Prerequisites - Hardware setup

hardware-prerequisite.jpg
|| Connect''' SMPS''' and '''USBasp''' to the '''Mainboard''' as shown in the picture.

Keep these connections throughout this tutorial.
|- 
|| Slide 6a: PWM instruction
* Can set the '''duty cycle''' of the PWM peripheral built into certain microcontrollers
* Duty cycle must be a number between 0 and 100

|| This sets the '''duty cycle''' of the '''PWM peripheral''' built into certain '''microcontrollers'''.


'''Duty cycle''' must be a number between 0 and 100.
|- 
|| Slide 6b: PWM instruction
* PWM frequency specified might not be exactly achievable.
* It depends on microcontroller's clock frequency

|| We can specify the '''PWM frequency''' in '''Hertz'''.

The '''frequency''' specified might not be exactly achievable.

It depends on how it divides into the '''microcontroller''''s '''clock frequency'''.
|- 
|| Show image of heater module
|| Here, we will create a '''logic''' to control the speed of a fan using '''PWM'''. 

We will use the fan in the '''Heater module'''.
|- 
|| Open the LDmicro from the launcher bar
|| Let us open '''LDmicro'''.
|- 
|| Click Instructions -> Insert Contact >> Place the cursor to the right of the contact >> Click Instructions -> Insert MOV 
|| Insert a '''Contact'''.

Place the cursor to the right of the '''Contact''' and insert a '''Move''' instruction.
|- 
|| Double-click on Xnew >> Type switch1 in the name box >> Click the OK button
|| Rename the '''Contact''' as '''‘switch1’'''.
|- 
|| Double-click on the MOV >> Set Destination to dc >> Set Source to 20 >> Click the OK button
|| In the '''move''' instruction, set the '''variable dc''' to 20.

Click on the '''OK''' button.
|- 
|| Click Edit -> Insert rung below >> Click Edit -> Insert rung below
|| Now, insert a '''rung''' below the current '''rung'''.
|- 
|| For both the rungs

Click Instructions -> Insert Contact >> Place the cursor to the right of the contact >> Click Instructions -> Insert MOV 
|| In the new '''rung''' insert a '''Contact''' and a '''Move''' instruction as shown.
|- 
|| Double-click on Xnew >> Type switch2 in the name box >> Click the OK button

Double-click on the MOV >> Set Destination to dc >> Set Source to 60 >> Click the OK button
|| Rename the '''Contact''' as '''‘switch2’'''.



In the '''Move''' instruction, set the '''variable dc''' to 60.
|- 
|| Click Edit -> Insert rung below >> Place the cursor in the new rung 
|| Insert one more '''rung''' below.

|- 
|| Insert Instructions -> Analog Operations -> Insert Set PWM output
|| Now, insert a '''PWM''' instruction from '''‘Analog Operations’''' as shown here.
|- 
|| Double-click on PWM 
|| Double-click on it.
|- 
|| Highlight two columns
|| We can find two columns.
|- 
|| Highlight Duty cycle variable 

Type dc 
|| First one is the '''duty cycle variable'''.

Set it to '''variable ‘dc’'''.
|- 
|| Highlight Frequency
|| Second is '''Frequency''' in '''Hertz'''.

By default, it is set to '''1kHz''' i.e. '''1000Hz'''. 

Do not change it.
|- 
|| Click the OK button
|| Click the '''OK''' button.
|- 
|| Highlight dc type in the I/O list
|| In the '''I/O list''' we can see the '''variable ‘dc’''' is of '''type PWM out.'''
|- 
|| 
|| We will now check the working of this '''logic'''.
|- 
|| Click Simulate -> Simulation mode >>

Click Simulate -> Real-time simulation
|| Let us turn '''on''' the '''simulation mode'''.

For that, click '''Simulate''' and then on '''Simulation mode.'''

Next, start '''real-time simulation''' as shown.
|- 
|| Highlight state column in the IO list
|| We can observe initially the states of all the instructions are 0.
|- 
|| Double click on Xswitch1 
|| Change the state of '''Xswitch1''' to 1 by double-clicking on it.
|- 
|| Highlight the value of dc
|| The '''variable dc''' is set to 20.
|- 
|| 

Highlight the value of dc

|| The '''dc variable''' value is set as the '''duty cycle''' of the '''PWM peripheral'''.

This happens when the '''input condition''' of '''PWM''' instruction is true.

In our case, it is true as the '''PWM''' instruction is connected to the '''positive rail'''.
|- 
|| Double click on Xswitch1 
|| Change the state of '''Xswitch1''' back to 0.
|- 
|| Double click on Xswitch2 

Highlight the value of dc

Double click on Xswitch2
|| Similarly, when '''Xswitch2''' state is 1 the '''duty cycle''' will be set to 60.
|- 
|| 
|| Make sure that at a time only one of the '''Contacts''' has its state 1.
|- 
|| Click Simulate -> Halt simulation >> Click Simulate -> Simulation Mode
|| Now, turn '''off''' the '''simulation mode'''.

For that, click '''Simulate''' and then on '''Halt Simulation.'''

Then click '''Simulate''' and '''Simulation Mode.'''
|- 
|| 
|| Now let us '''compile''' the '''logic'''.
|- 
|| Click on Settings >> Click on Microcontroller >> Select AVR ATmega16 40-PDIP 

Click on Settings >> Click on MCU parameters >> Change Crystal frequency to 16
|| Click on '''Settings''' and select the '''microcontroller AVR ATmega16 40-PDIP.''' 


Adjust its '''parameters''' as shown here.
|- 
|| Highlight ‘dc’ in the I/O list
|| We can see that '''variable dc''' is already assigned '''pin''' number 21, which is '''PD7'''.

This is the '''PWM pin''' for '''ATMega16 microcontroller'''.
|- 
|| Double-click on Xswitch1 in I/O list >> Select PC7 >> Click OK button

Double-click on Xswitch2 in I/O list >> Select PC6 >> Click OK button
|| Now assign '''PC0''' to '''Xswitch1 '''and '''PC1''' to '''Xswitch2''' as shown.

|- 
|| Click on Compile >> Click on Compile >> rename it as ‘pwm.hex’ >> Go to Desktop/LDmicro folder >> Click on Save.

Click OK button
|| Compile the '''logic''' as''' pwm.hex'''
|- 
|| Click on File >> Click on Save >> Rename it as ‘pwm.ld’ >> Go to Desktop/LDmicro folder >> Click on Save
|| Save the '''ladder diagram''' as '''pwm.ld'''
|- 
|| 
|| We will now see the working of this '''logic''' on hardware.
|- 
|| Connect Mainboard to PC using USBasp

laptop-usbasp.jpg

|| Connect the '''Mainboard''' to your laptop using '''USBasp'''.

Turn '''on''' the '''power supply'''.
|- 
|| Open terminal >> Type cd Desktop/LDmicro >> Press ENTER >> type ‘'''avrdude -c usbasp -p m16 -U flash:w:pwm.hex’ '''>> Press ENTER
|| Open the '''Terminal''' by pressing '''CTRL+ALT+T''' keys simultaneously.

Go to the folder where you have saved the '''hex file'''.

Type the '''command''' as shown to upload the '''hex file''' to the '''Mainboard'''.
|- 
|| Remove the '''USBasp''' connection from the laptop.
|| Turn '''off''' the '''power supply'''.

Remove the '''USBasp''' connection from the laptop.

This will prevent any hardware damage.
|- 
|| pwm.png
|| Let us see the connection details now. 
|- 
|| pwm.png

Make the connections as shown in the picture.

|| Power the''' Heater module''' through '''relimate connectors''' from the '''Mainboard'''.

Connect '''PD7''' to the fan '''pin''' of the '''MCU pins''' of the '''Heater module.'''
|- 
|| pwm.png  

Make the connections as shown in the picture.

|| Connect '''GND''' and '''5V''' of the '''Switchboard''' to '''GND''' and '''5V''' of the '''Mainboard''' respectively.

Then connect '''NO1''' to '''PC0''' and '''NO2''' to '''PC1 '''of the '''Mainboard'''.

Make the connections as shown in the picture.
|- 
|| Turn '''on''' the '''power supply'''.
|| After making all the connections properly, turn '''on''' the '''power supply'''.
|- 
|| 

Press the switch '''NO1'''.


|| Initially the fan will be '''off''' as the '''duty cycle''' is 0.

The '''FANon LED''' on the '''Heater module''' would be glowing dim.

Press the switch '''NO1'''.

We can observe the fan is turned '''ON'''.

The '''duty cycle''' is 20 here.
|- 
|| Press the switch '''NO2'''
|| Now press the switch '''NO2'''.

We can observe the speed of the fan is increasing comparatively.

This is because of the increase in the '''duty cycle''' to 60.
|- 
|| 
|| Thus we have controlled the speed of the fan using '''PWM'''.
|- 
|| Turn '''off''' the '''power supply'''.
|| Turn '''off''' the '''power supply'''.
|- 
|| 
|| This brings us to the end of this tutorial.

Let us summarize.
|- 
|| Slide 8: Summary
* PWM instruction

|| In this tutorial we learnt about working of '''PWM''' instruction

|- 
|| Slide 9:

Assignment: 

|| As an assignment,

Control the brightness of the red '''LED''' of '''Traffic Light module'''.

Hints: 
#Replace fan of '''Heater module''' with red '''LED''' of '''Traffic light module'''.
#Connect '''PD7 pin''' to '''+5V pin''' of the red '''LED''' of the '''Traffic Light module'''.
|- 
|| Slide 10:

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

Please download and watch it.
|- 
|| Slide 11:

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 11:

Forum for specific questions:
|| Please post your timed queries in this forum.

|- 
|| Slide 12:

Forum for specific questions:
|| Do you have any general / technical questions on OpenPLC?

Please visit the FOSSEE forum and post your question.
|- 
|| Slide 13:

Acknowledgement
|| Spoken Tutorial Project is funded by MHRD, Government of India.
|- 
|| Slide 14:

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.
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