1. PRESENTED BY:
 MUQADSA IFTIKHAR CLASS NO. 03 REG. NO (09ABELT0290)
 ZUNAIB ALI CLASS NO. 09 REG. NO (09ABELT0296)
Supervised BY:
 ENGR. SANIA SAEED

2. ABSTRACT
• The purpose of a motor speed control is to take a
signal representing the demanded speed and drive the
motor at that speed.

3. INTRODUCTION
 The speed of dc motor is directly proportional to the supply
voltage, if we reduce the supply voltage from 12V to 6V, the
motor will run at half the speed.
 SCR “phase-angle controlled” drive -By changing the firing
angle, variable DC output voltage can be obtained.
 Here we are using microcontroller applications. For this we
are using AT89C51 IC and by using this we are setting the
speed of motor.

4. MAIN COMPONENTS
1. 220 V , 50Hz AC Supply
2. Step Down Transformer
3. DC motor
4. Micro controller
5. Thyristor (SCR)
6. NPN Transistor
7. Crystal Oscillator (11.0592MHz)
8. 5V DC Supply

5. DC MOTOR
 The DC motor is electric motor that runs on direct current electrically.
 DC motor works based on the LORENTZ FORCE.
 In DC motor voltage is proportional to speed
ADVANTAGES
 Low initial cost
 High reliability
 Simple control of motor speed

6. Block Diagram

7. Zero Crossing Detector
0 2 t
0 9ms 18ms t
Sinusoidal input
t
0 2 3
Zero Detector Output

8. Micro- Controller AT89c51
 A smaller computer
 On-chip RAM, ROM, I/O ports.
CPU RAM ROM
Serial
I/O Timer COM
Port
Port
A single chip
Microcontroller

9. CIRCUIT DIAGRAM

10. AT89C51 Programming:
#include <reg51.h> case 1:
unsigned char x, y; x=0x66;
sbit driv = P2^2; y=0xFC;
void main()
break;
{
P1=255; case 2:
P2=0x00; x=0xCC;
IE=0x81; y=0xF8;
break;
while(1)
case 3:
{
switch (P1) x=0x33;
{ y=0xF5;
case 0: break;
x=0xFF; case 4:
y=0xFF;
x=0x99;
break;
y=0xF1;
break;

11. Continue…
case 5: case 9:
x=0xFF; x=0x99;
y=0xED; y=0xDF;
break; break;
case 6: }
x=0x66; }
y=0xEA; }
break;
case 7: void External0(void) interrupt 0
x=0xCC;
y=0xE6; {
break; driv =0;
case 8: TMOD=0x10;
x=0x32; TL1=x;
y=0xE3; TH1=y;
TR1=1;
break;

12. Continue…
while(TF1==0);
TR1=0;
TF1=0;
driv=1;
TMOD=0x01;
TL0=0xCC;
TH0=0xF8;
TR0=1;
while(TF0==0);
TR0=0;
TF0=0;
driv=0;
}

13. Explanation:
 Input 220V, 50Hz is step down to
30V, 50Hz.
 This 30V, 50Hz is applied to Controlled
HWR with DC motor as load.
 For the gating circuitry the same input
30V, 50Hz is applied to zero crossing
detector to generate an external
interrupt.
 Logic states are used to provide firing
angle α.
 When the external interrupt occurs
micro-controller generates pulse
according to provided α.

14. Outputs for Different Firing Angle:
For α = 0
Voltage Across Motor HWR Rectifier Output

15. Continue…
For α = 7ms
Voltage Across Motor HWR Rectifier Output

16. Continue…
For α = 3ms
Voltage Across Motor HWR Rectifier Output

17. Software Simulation:

18. Extension of Our Project

19. Applications
 ROBOTIC CONTROLS.
 SWING MACHINES.
 ELECTRONIC BIKES.
 WINDING MACHINES.
 DC OPERATED DRILL MACHINES.
 MOBILE AIR CONDITION FANS.
 TOYS.
 ELCTRONIC DOOR CONTROLLERS.
 ELECTRONIC CHAIRS (beauty parlor etc.)

20. CONCLUSION
 We have achieved the required speed and thyristor is
a very good device for obtaining the variable DC there
by controlling the motor speed.
 This circuit is just a basic circuit for understanding DC
motor speed control. In case of HWR we got zero
voltage in negative half cycle that’s why has power
efficiency.

21. Any query