AVR_Course_Day8 motor drive and pwm techniques

Motor Drive and PWM Techniques

Eng:Mohamed Loay Ali

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Contents DC Motor

1. Introduction to DC motor and its parameters. 2. PWM 8 bits modes (Fast PWM &Phase Correct).3. PWM 16 bits modes (Fast PWM & Phase Correct).4. Speed Control of DC motor.

Stepper motor.1. Stepper motor basics.2. Main Components of Stepper motor.3. Types of Stepping Motors4. Unipolar and Bipolar Stepper Motors5. Driving Stepper motor.


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DC motor1. Introduction to DC motor and its parameters.

A direct current motor one of the most widely used motors. By connecting the motor terminal to dc source it rotates in one direction,

and by reversing the polarity it rotates to the opposite direction. The maximum speed of a dc motor is indicated with the rpm and is

given in the data sheet. The dc motor control can be unidirectional or bidirectional as shown in

the following figure


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The speed of the motor depends on three factors1) Load.2) Voltage.3) Current. The rpm of the motor can be controlled by varying the voltage

terminals. For a given fixed load a steady speed can be maintained by using

Pulse width modulation (PWM) to change the voltage across the DC terminals.

Although the PWM has a fixed amplitude, it has a variable duty cycle. That means the wider pulse the wider the higher the speed.

By varying the duty cycle the power fed to the motor speed is changing as shown in the following


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DC motorPWM 8 bits modes : Fast PWM


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DC motorPWM 8 bits modes : Fast PWM The counter counts up like it does in the normal mode. It counts up until it reaches its maximum value 0xFF. Then it rolls over to from 0xFF to 0x00 ,it set the TOV The fast PWM differs from the other PWM option by its single-slope operation. In non-inverting Compare Output mode, the Output Compare (OC0x) is cleared

on the compare match between TCNT0 and OCR0x, and set at BOTTOM. In inverting Compare Output mode, the output is set on compare match and

cleared at BOTTOM.


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DC motorPWM 8 bits modes :PWM 8 bits modes : Fast PWM


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DC motor

For non-Inverted mode

For Inverted mode

PWM 8 bits modes : Fast PWM


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DC motorPWM 8 bits modes : Phase Correct The phase correct PWM mode (WGM02:0 = 1 or 5) provides a high resolution. The counter counts repeatedly from BOTTOM to TOP and then from TOP to

BOTTOM. TOP is defined as 0xFF when WGM2:0 = 1and OCR0A when WGM2:0 = 5

In non-inverting Compare Output mode, the Output Compare (OC0x) is cleared on the com-pare match between TCNT0 and OCR0x while up counting, and set on the compare match while down counting.

In inverting Output Compare mode, the operation is inverted. The dual-slope operation has lower maximum operation frequency than single slope operation


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DC motorDC motorPWM 8 bits modes : Phase Correct


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DC motorPWM 8 bits modes : Phase Correct

For non-Inverted mode

For Inverted mode


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DC motorPWM 8 bits modes : Phase Correct


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DC motor PWM 16 bits modes (Fast PWM & Phase Correct). Speed Control of DC motor.

DO IT Yourself


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Stepper Motor1. Stepper motor basics.

Stepper Motor are motors that moves one step at a time. A digital version of an electric motor Each step is defined by a Step Angle


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Stepper Motor1. Stepper motor basics.

Relatively inexpensive Ideal for open loop positioning control Can be implemented without feedback Minimizes sensing devices Just count the steps!

Torque Holds its position firmly when not turning Eliminates mechanical brakes Produces better torque than DC motors at lower speeds

Positioning applications


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Stepper Motor2.Main Components of Stepper motor.

Consists of 1.Stator:Holds multiplewindings/phases


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Consists of 2.Rotor:Magnetizedor non-magntized


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Voltage applied to winding initiates current flow Magnetic flux begins to flow


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Rotor rotates to minimize flux path (or reluctance)


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Stepper Motor3.Types of Stepping Motors

Permanent MagnetMagnetic rotor

Variable ReluctanceNon-magnetic, geared rotor

HybridCombines characteristics from PM and VRMagnetic, geared rotor


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Permanent Magnet


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Variable ReluctanceNon-magnetic, geared rotor


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HybridCombines characteristics from PM and VR Magnetic, geared rotor


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4.Unipolar and Bipolar Stepper Motors

Stepper Motor

Leads on each coil can be brought out in two ways:−Each lead taken separately−Bi-directional current flow through entire winding


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4.Unipolar and Bipolar Stepper Motors

Stepper Motor

A center tap added between the two leads−Unidirectional current flow in each ½ of windingUnipolar


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5.Driving Stepper motor(Bipolar Full Step).

Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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5.Driving Stepper motor(Bipolar Full Step two phase on).

Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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5.Driving Stepper motor(Bipolar half Step).

Stepper Motor

Combines “One Phase On” and “Two Phase On” algorithms

Improves rotational resolution Minimizes anti-resonance


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor


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Stepper Motor5.Driving Stepper motor(Unipolar half Step).

Center Tap connected to Ground or Voltage Source. Current flows in ½winding at a time.


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Stepper Motor5.Driving Stepper motor(Unipolar).


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Stepper Motor5.Driving Stepper motor(Bipolar Drive Circuit).


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Stepper Motor5.Driving Stepper motor(Uni-polar Drive Circuit).


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Engineering

AVR_Course_Day8 motor drive and pwm techniques