dc & stepper motor

A Seminar presentation on:DC & Stepper motor

Deepankar [email protected]: 09695027623

ELECTRIC MOTORSELECTRIC MOTORS

An Introduction to DC and An Introduction to DC and Stepper MotorsStepper Motors

Electric MotorsElectric Motors

• Electric motors are Electric motors are everywhere! everywhere!

• In your house, In your house, almost every almost every mechanical mechanical movement that you movement that you see around you is see around you is caused by an AC or caused by an AC or DC electric motor. DC electric motor.

Direct Current MotorsDirect Current Motors

• overall plan of a simple 2-pole DC electric motor

• A simple motor has 6 parts, as shown in the diagram

Direct Current MotorsDirect Current Motors

Brushed DC MotorBrushed DC Motor

• The brushed DC The brushed DC motor is one of the motor is one of the earliest electric earliest electric motor designsmotor designs

• Easy to understand Easy to understand design design

• Easy to control Easy to control speed speed

DC STEPPER MOTORSDC STEPPER MOTORS

• Stepping motors are electric motors without commutators

• Commutation is handled externally by the motor controller

• Controller charges opposite coils attracting the center rotor magnets


• Voltage Rating Voltage Rating – provides desired torqueprovides desired torque

• Resistance-per-winding Resistance-per-winding determinesdetermines– the current draw of the motorthe current draw of the motor– Maximum operating speedMaximum operating speed

• Degrees per StepDegrees per Step– Sets the number of degrees the shaft Sets the number of degrees the shaft

will rotate for each full stepwill rotate for each full step

UNIPOLAR STEPPER UNIPOLAR STEPPER MOTORMOTOR

• Relatively easy to controlRelatively easy to control• simple 1-of-'n' counter circuit can generate simple 1-of-'n' counter circuit can generate

the proper stepping sequencethe proper stepping sequence• 1 transistor per winding1 transistor per winding


• two center-tapped coilstwo center-tapped coils• represents the connection of a 4 -phase represents the connection of a 4 -phase

unipolar stepper motorunipolar stepper motor

Cont...Cont...

Current flow is limited in Current flow is limited in one direction one direction

To rotate the motor, just To rotate the motor, just apply power to the two apply power to the two windings in sequencewindings in sequence


• 6 wires with a center tap on each of two coils6 wires with a center tap on each of two coils

IDENTIFYING WIRESIDENTIFYING WIRES

• Check make and model to see if Check make and model to see if wire colour code is availablewire colour code is available

• Observe the wires to see if you can Observe the wires to see if you can identify groups of 3 wiresidentify groups of 3 wires

• Measure resistance between wires Measure resistance between wires • Wire with lowest resistance is Wire with lowest resistance is

power wirepower wire

IDENTIFYING WIRESIDENTIFYING WIRES

• 6 wire motors6 wire motors– Groups of 3 wiresGroups of 3 wires– 1 power & 2 signal1 power & 2 signal

• 5 wire motors5 wire motors– 1 power & 4 signal wires1 power & 4 signal wires

• power wire has power wire has lowest lowest resistance to the resistance to the othersothers

STEPPER MOTOR STEPPER MOTOR CONTROLCONTROL

• 4 signal wires fired in the correct sequence will 4 signal wires fired in the correct sequence will turn the motorturn the motor

Modes of Stepper Motor:Modes of Stepper Motor:

Full StepFull Step

Half StepHalf Step

Micro StepMicro Step

Full step mode:Full step mode:

The center taps of The center taps of the windings are the windings are wired to the positive wired to the positive supplysupply

The two ends of each The two ends of each winding are winding are alternately grounded alternately grounded to reverse the to reverse the direction of the field direction of the field provided by that provided by that winding winding

Cont…Cont…

Full step sequence Full step sequence showing how binary showing how binary numbers can control numbers can control the motorthe motor

Half step mode:Half step mode:

Same circuitry with Same circuitry with

Different winding Different winding sequencesequence

Two windings are Two windings are energized at the energized at the same instancesame instance

Cont…Cont…

Half step sequence showing how binary Half step sequence showing how binary numbers can control the motornumbers can control the motor

Micro Stepping Mode:Micro Stepping Mode:

• Positional resolution is limited Positional resolution is limited because of the mechanical design because of the mechanical design of the unit of the unit

• It allows a stepping motor to stop It allows a stepping motor to stop and hold a position between the and hold a position between the full or half-step positions full or half-step positions

Cont…Cont…

• The jerky character of low speed The jerky character of low speed stepping motor operation and the stepping motor operation and the noise at intermediate speeds noise at intermediate speeds

dc & stepper motor

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