We can control the speed of a DC motor through a microcontroller. All we need to know about PWM .That means "

**Pulse Width Modulation**". It is a very popular technique and most important part of a microcontroller. In this tutorial we will use PWM to create signal. By changing pulse width of a signal ,we can control the speed .

## Basic Description:

At first we will connect a DC motor with PIC microcontroller and we will also connect two push buttons with it. One of those buttons will be used for increasing speed and another one for decreasing speed. That's all .
Now listen to me carefully, Just keep this in your mind

1. Increasing duty or Pulse Width will increase the speed of DC motor .

2.Decreasing duty or Pulse Width will decreasing the speed of DC motor.

Now, we need to know about PWM [ Pulse Width Modulation ]

## Pulse Width Modulation (PWM)

Pulse width modulation |

when Set_Duty(127); |

PWM |

**PWM**or

**CPP**module look at the picture .

In

**L293D**'s

**EN1**pin we provide the signal. If you will provide highest pulse width, the speed will be highest. When you will decrease pulse width, the speed will also be decreased.

So if you don't know how to interface DC motor with microcontroller. It's recommended to read this tutorial ,

## DC Motor Interfacing with PIC Microcontroller in Proteus [step by step]

Time Period = Times of ON state + Times of OFF state .

###
**PWM has four functions **

####
**1. PWM1_Init( Set_Frequency );**

####
**2. PWM1_Start(); **

####
**3.PWM1_Set_Duty( Count );**

####
**4.****PWM1_Stop()**;

Here most important thing is PWM1_Set_Duty(count) , If we increase the value of count, the speed increases. If we decrease the value of count, the speed decreases. Another important thing is the highest value of count is 255 and lowest is 0.**PWM1_Stop()**;

**count**proportional to

**PW**

So,

**count = K * PW ----eq(1)**where

**K = constant .**

**count/PW=K**

When

**PW=T , count=255**and when

**PW=T/2 , count=127.5 or 127**

255/T=127/(T/2) = K

**and , inserting values of PW and count in eq(1)**

255=K * T----eq(2)

127.5=K * (T/2)------eq(3)

Now eq(2)+eq(3) : 382.5= K { T +(T/2)}

or 382.5=K*(3T/2)

or 765=3*K*T

or T*K=255

or K=255/T

Now inserting value of K into eq(1) , we get

**Finally we get, count =255*(PW/T)**, This is the relation between count, PW & T.

That was not very necessary for this tutorial. But I've shared all I knew.

When pulse width is equal to T it means total time period it remains ON . Now look at the picture given below :

Now create a project in proteus

## # Proteus Circuit :

## #MikroC Code :

```
void main() {
unsigned int count=0;
ADCON1=0x0F;
CMCON=7;
TRISA.F0=1;
TRISA.F1=1;
TRISC.F1=0;
TRISC.F0=0;
PWM1_Init(1000);
PWM1_Start();
PORTC.F0=1;
PORTC.F1=0;
PWM1_set_duty(count);
while(1){
if(PORTA.F0==0){
delay_ms(100);
if(count>=255) {
count=255; }else{
count=count+15;
PWM1_set_duty(count);
}
}
if(PORTA.F1==0){
delay_ms(100);
if(count<=0){
count=0; }else{
count=count-15;
PWM1_set_duty(count);
}
}
}
}
```

Hello Mr. I need CCS code for this pwm control.... is it possible give me changed it? Thank you.

ReplyDeletettt

ReplyDelete