Motor and High Power Interfaces

1
Motor and High Power Interfaces

• We have seen how to use various on-chip
  peripherals (Timer, interrupts, etc)
• We have seen how to interface various peripherals
  (A/D, D/A, Serial EE, LCD, etc)
• Embedded system often need to integrate into
  electromechanical systems
• User interface - keypads, buttons, etc
• Actuators motors, solenoids, etc

2
Actuators

• Motors
• Spindle usually velocity or torque regulated
• Servo often position regulated
• Stepper position
• Regardless of configuration, motors always
  require more current than a microcontroller can
  deliver, hence the need for specialized
  interfaces

3
(DC) Spindle / Servo Motors

• Generally of a permanent magnet design

4
Driving Motors

• µPs 5 volt (or 3.3 volt) I/O current limited at
  around 20 mA wont do much for a motor.
• Need to use I/O to switch higher voltage /
  current to motor
• Relay (motor contactor)
• These have coils too
• Be careful
• Transistor
• How about reverse?
• Feedback how fast is motor turning?

5
L293D
6
L293D

• 36 VDC motors
• 1.2A peak, 600 mA continuous
• Integrated clamp diodes
• Other options
• L298
• 46 volts
• 4 amps

7
Any Size

• Isolation may become an issue.
• Optical is a good choice.

8
Stepper Motors

• Special motor design
• Motor lines up with flux of coils
• Two types
• Unipolar
• Bipolar
• Advantages
• Can run open loop and still know position
• Can hold a stationary position
• Disadvantages
• Not smooth for continuous operation
• More difficult to program
• Not all that high of a velocity