SPEED CONTROL OF DC MOTOR
PRESENTED BY:
MUQADSA IFTIKHAR CLASS NO. 03 REG. NO (09ABELT0290)
ZUNAIB ALI CLASS NO. 09 REG. NO (09ABELT0296)
Supervised BY:
ENGR. SANIA SAEED
ABSTRACT
• The purpose of a motor speed control is to
take a signal representing the demanded
speed and drive the motor at that speed.
INTRODUCTIONThe 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.
MAIN COMPONENTS1. 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
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
Block Diagram
Zero Crossing Detector
0 20 9ms 18ms
tt
0
2
0
9ms
18ms
t
t
t20 3
Sinusoidal input
Zero Detector Output
Micro- Controller AT89c51 A smaller computer
On-chip RAM, ROM, I/O ports.
RAM ROM
I/O Port
TimerSerial COM Port
Microcontroller
CPU
A single chip
CIRCUIT DIAGRAM
AT89C51 Programming:#include <reg51.h>
unsigned char x, y;sbit driv = P2^2;
void main(){
P1=255;P2=0x00;IE=0x81;
while(1){switch (P1){
case 0:x=0xFF;y=0xFF;break;
case 1:x=0x66;y=0xFC;break;
case 2:x=0xCC;y=0xF8;break;
case 3:x=0x33;y=0xF5;break;
case 4:x=0x99;y=0xF1;break;
case 5:x=0xFF;y=0xED;break;
case 6:x=0x66;y=0xEA;break;
case 7:x=0xCC;y=0xE6;break;
case 8:x=0x32;y=0xE3;break;
case 9:x=0x99;y=0xDF;break;
} } }
void External0(void) interrupt 0
{ driv =0;TMOD=0x10;TL1=x;TH1=y;TR1=1;
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;
}
Continue…
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.
Outputs for Different Firing Angle:
Voltage Across Motor HWR Rectifier Output
For α = 0
Continue…
Voltage Across Motor HWR Rectifier Output
For α = 7ms
Continue…
Voltage Across Motor HWR Rectifier Output
For α = 3ms
Software Simulation:
Extension of Our Project
BRIDGERECTIFER
FILTER
5V REGULATOR
12V REGULATOR MOTOR
MOSFET
SENSORCOMPARATOR
+5V+5V
GNDGND
MICROCONTROLLERLCD16X2
+5V
+5VGND
GND
RSRWEN
D4D5D6D7
TRANSFORMER
UP_SWUP_SW
ApplicationsROBOTIC CONTROLS.SWING MACHINES.ELECTRONIC BIKES.WINDING MACHINES.DC OPERATED DRILL MACHINES.MOBILE AIR CONDITION FANS.TOYS.ELCTRONIC DOOR CONTROLLERS. ELECTRONIC CHAIRS (beauty parlor etc.)
CONCLUSIONWe 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.
Any query
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