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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.
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.
MAIN COMPONENTS1. 220 V , 50Hz AC Supply2. Step Down Transformer3. DC motor4. Micro controller5. Thyristor (SCR)6. NPN Transistor7. 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 speedADVANTAGES Low initial cost High reliability Simple control of motor speed
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:For α = 0 Voltage Across Motor HWR Rectifier Output
Continue…For α = 7ms Voltage Across Motor HWR Rectifier Output
Continue…For α = 3ms Voltage Across Motor HWR Rectifier Output
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.)
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.