Lecture6 - microprocessors two -Motors.ppt
- 1. Motors
- 2. Components Microprocessor SRAM Flash Memory Input ports Output ports Parallel Serial Sensor Motor Siren DAC ADC Rom Microprocessor
- 3. DC Motor
- 5. Figure 12-6 Rotor Alignment Every stepper motor has a permanent magnet rotor (shaft) surrounded by a stator. INTERFACING TO A STEPPER MOTOR stepper motors • A stepper motor translates electrical pulses into mechanical movement. – Used for position control in disk drives, printers & robotics.
- 7. Unipolar stepper motor – Full step
- 8. Unipolar stepper motor – Half step
- 11. INTERFACING TO A STEPPER MOTOR stepper motors • Most common stepper motors have four stator windings, paired with a center-tapped common. – Commonly referred to as a four-phase stepper motor. Stator Windings Configuration The center tap allows the change of current direction in each of two coils when a winding is grounded, causing a polarity change of the stator. The shaft moves in a fixed repeatable increment, allowing precise positioning, with direction of rotation dictated by the stator poles.
- 12. INTERFACING TO A STEPPER MOTOR stepper motors • This stepper motor has four leads representing the four stator windings, and two commons for the center tapped leads. • As the sequence of power is applied to each stator winding, the rotor will rotate. – Once started, sequence must continue in the proper order.
- 13. INTERFACING TO A STEPPER MOTOR motor speed/holding torque/wave drive • The motor speed, measured in steps per second (steps/s), is a function of the switching rate. – Torque is measured with rated voltage and current applied to the motor, in ounce- inch (or kg-cm) units. • In addition to the 8- & 4-step sequences, there is also the wave drive 4- step sequence.
- 14. INTERFACING TO A STEPPER MOTOR step angle • Movement is associated with a single step depends on internal construction of the motor. – In particular the number of teeth on the stator & rotor. The step angle is the minimum degree of rotation associated with a single step. Various motors have different step angles.
- 16. INTERFACING TO A STEPPER MOTOR step angle • Steps per revolution is the total number of steps needed to rotate one complete rotation, or 360 degrees (e.g., 180 steps x 2 degrees = 360). • A stepper motor does not need to have more terminal leads for the stator to achieve smaller steps. – While some manufacturers have set aside only one lead for the common signal instead of two, they always have four leads for the stators.
- 17. INTERFACING TO A STEPPER MOTOR steps per second and RPM relation • The relationship between the RPM (revolutions per minute), steps per revolution, and steps per second is intuitive, and is as follows:
- 18. Floppy disk stepper motor
- 19. ULN2003A
- 20. INTERFACING TO A STEPPER MOTOR stepper motor connection and programming Example 12-2, on page 328, shows programming of the stepper motor as connected in Fig. 12-8. This example contains some very important points on motor interfacing. Fig. 12-8 8255 Connection to Stepper Motor
- 22. Wiring 5-Wire Motor • This style is common in smaller unipolar motors. All of the common coil wires are tied together internally and brought out as a 5th wire. This motor can only be driven as a unipolar motor.
- 23. Wiring 6-Wire Motor • This motor only joins the common wires of 2 paired phases. These two wires can be joined to create a 5-wire unipolar motor. Or you just can ignore them and treat it like a bipolar motor!
- 24. Wiring 8-Wire Motor • The 8-wire unipolar is the most versatile motor of all. It can be driven in several ways: 4-phase unipolar - All the common wires are connected together - just like a 5-wire motor. • 2-phase series bipolar - The phases are connected in series - just like a 6-wire motor. • 2-phase parallel bipolar - The phases are connected in parallel. This results in half the resistance and inductance - but requires twice the current to drive. The advantage of this wiring is higher torque and top speed.
- 26. Servo Motor