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Report no.4(microprocessor)

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  • 1. Date: 20/11/2013 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
  • 2.  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. 2. 3. 4. Permanent magnet stepper. Hybrid synchronous stepper. Variable reluctance stepper. 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
  • 3. unipolar motors popular with hobbyists; they are probably the cheapest way to get precise angular movements. Fig-1Unipolar 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-2Full step- stepper motor
  • 4.  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- 3Half step- stepper motor Fig -4Full and half clockwise rotation  advantages of stepper motors: 1. 2. 3. 4. 5. 6. 7. the rotation angle of the motor is proportional to the input pulse. Excellent response to starting, stopping, and reversing. The motors response to digital input pulses provides open-loop control. It's possible to achieve very low speed synchronous rotation. A wide range of rotational speeds can be real realized. Very reliable since there no contact brushes in the motor. Accuracy of 3-5% of a step and this error is non cumulative from one step to the next.  ULN2003A ICs:
  • 5. 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 -5ULN2003A ICs  Experiment:
  • 6.  Control circuit: Fig-6Stepper motor circuit Fig-7Stepper motor circuit  Experiment no.1: Control code: Fig-8Visual basic form to control stepper motor
  • 7. 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
  • 8. 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- -
  • 9.  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:

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