Al-Azhar University-Gaza

Faculty of Engineering & Information Technology

Mechatronices engineering

Microprocessors & Interfacing

(ITCE 3306)

LAB NO.4

Stepper motor

Prepared By:

Ronza sameer Abu jayyab

No. 20111511

Submitted To:

Eng. Mahmoud I. Hasanain

First semester

2013/2014

Date: 20/11/2013

introduction: we will deal with steeper motor which is,

electromechanical device which converts electrical pulses into discrete

mechanical movements.

Shaft of a steeper motor rotates in discrete step increments when electrical

pulses are applied.

Sequence of the applied pulses is directly related to the direction of motor

shaft's rotation.

Speed of rotation is directly related to the frequency of input pulses applied.

objective: after this lab we're being able to answer these questions,

1. what is the stepper motor and from what it consist also who it is work?

2. how we can deal with stepper motor ?

3. How can you connect stepper motor with parallel port to make computer

interfacing?

background:

stepper motor:

types of stepper motor:

There are four main types of stepper motors:

1. Permanent magnet stepper.

2. Hybrid synchronous stepper.

3. Variable reluctance stepper.

4. Lavet type stepping motor.

Two-phase stepper motors:

1. Unipolar steeper motor.

2. Bipolar steeper motor.

Unipolar steeper motor:

A unipolar stepper motor has one winding with center tap per phase. Each

section of windings is switched on for each direction of magnetic field.

Since in this arrangement a magnetic pole can be reversed without

switching the direction of current, the commutation circuit can be made

very simple (e.g., a single transistor) for each winding. Typically, given a

phase, the center tap of each winding is made common: giving three leads

per phase and six leads for a typical two phase motor. Often, these two

phase commons are internally joined, so the motor has only five leads.

A micro controller or stepper motor controller can be used to activate the

drive transistors in the right order, and this ease of operation makes

unipolar motors popular with hobbyists; they are probably the cheapest

way to get precise angular movements.

Fig-1-

Unipolar stepper motor coils

(For the experimenter, the windings can be identified by touching the

terminal wires together in PM motors. If the terminals of a coil are

connected, the shaft becomes harder to turn. one way to distinguish the

center tap (common wire) from a coil-end wire is by measuring the

resistance. Resistance between common wire and coil-end wire is always

half of what it is between coil-end and coil-end wires. This is because

there is twice the length of coil between the ends and only half from center

(common wire) to the end.) A quick way to determine if the stepper motor

is working is to short circuit every two pairs and try turning the shaft,

whenever a higher than normal resistance is felt, it indicates that the circuit

to the particular winding is closed and that the phase is working.

Modes of Stepper Motor:

1. Full step.

2. Half step.

Full step:

1. The center taps of the windings are wired to the positive supply.

2. The two ends of each winding are alternately grounded to reverse

the direction of the field provided by that winding.

3. Full step sequence showing how binary numbers can control the

motor.

Fig-2-

Full step- stepper motor

Half step:

1. Same circuity with different winding sequence.

2. Two windings are energized at the same instance.

3. Half step sequence showing how binary numbers can control the

motor.

Fig- 3-

Half step- stepper motor

Fig -4-

Full and half clockwise rotation

advantages of stepper motors:

1. the rotation angle of the motor is proportional to the input pulse.

2. Excellent response to starting, stopping, and reversing.

3. The motors response to digital input pulses provides open-loop control.

4. It's possible to achieve very low speed synchronous rotation.

5. A wide range of rotational speeds can be real realized.

6. Very reliable since there no contact brushes in the motor.

7. Accuracy of 3-5% of a step and this error is non cumulative from one step to

the next.

ULN2003A ICs:

An ULN2003A is a high-voltage, high-current Darlington transistor array.

It consists of seven NPN Darlington pairs that feature high-voltage outputs with

common-cathode flyback diodes for switching inductive loads.

It is very similar to the ULN2801A, ULN2802A, ULN2803A,[3] ULN2804A, and

ULN2805A, only differing in logic input levels (TTL, CMOS, PMOS) and number of

inputs (8).

The drivers can be paralleled for higher current capability, even stacking

one chip on top of another, both electrically and physically has been done.

Features

500 mA rated collector current (single output)

50 V output

Includes output flyback diodes

Inputs compatible with various types of logic

Application:

Typical usage of the ULN2003A is to:

1. drive relays.

2. lamp and LED displays.

3. stepper motors.

Fig -5-

ULN2003A ICs

Experiment:

Control circuit:

Fig-6-

Stepper motor circuit

Fig-7-

Stepper motor circuit

Experiment no.1:

Control code:

Fig-8-

Visual basic form to control stepper motor

Dim i As Integer

Private Sub Command1_Click()

Timer1.Enabled = True

Timer2.Enabled = False

Timer1.Interval = 5

Timer2.Interval = 5

End Sub

Private Sub Command2_Click()

Timer1.Enabled = False

Timer2.Enabled = True

Timer1.Interval = 5

Timer2.Interval = 5

End Sub

Private Sub Form_Load()

ntport1.address = 888

End Sub

Private Sub Timer1_Timer()

ntport1.Value = 2 ^ i

i = i + 1

If i > 7 Then i = 0

End Sub

Private Sub Timer2_Timer()

ntport1.Value = 2 ^ i

i = i - 1

If i < 0 Then i = 7

End Sub

Comment: Stepper motor move clockwise fast by timer 1 and counter clockwise fast by

timer 2.

When decrease value of interval stepper motor will move fast.

Experiment no.2:

Control code:

Dim i As Integer

Private Sub Command1_Click()

Timer1.Enabled = True

Timer2.Enabled = False

Timer1.Interval = 50

Timer2.Interval = 50

End Sub

Private Sub Command2_Click()

Timer1.Enabled = False

Timer2.Enabled = True

Timer1.Interval = 5

Timer2.Interval = 5

End Sub

Private Sub Form_Load()

ntport1.address = 888

End Sub

Private Sub Timer1_Timer()

ntport1.Value = 2 ^ i

i = i + 1

If i > 7 Then i = 0

End Sub

Private Sub Timer2_Timer()

ntport1.Value = 2 ^ i

i = i - 1

If i < 0 Then i = 7

End Sub

Comment: Stepper motor move clockwise slow by timer 1 and counter clockwise slow by

timer 2.

When increase value of interval stepper motor will move slow.

Fig- -

Conclusion: a. All types and characteristics of a stepper motor are studied throughout this

report.

b. These are very popular in our day to day life due to a lot of advantages and also

in digital control circuits, such as robotics because they are ideally suited for

receiving digital pulses for ste.

References: