ECET 340 Week 7 HomeWork 7

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DEVRY ECET 340 Week 7 HomeWork 7

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• 1. The movable part of the solenoid is the 2
  points
• 2. Why is the 6N139 optoisolator used in the
  interfaces to devices such as large motors? 2
  points
• 3. Calculate the number of steps per revolution
  for a stepper motor with a step angle of 7.5. 2
  points

2

• 4. How is stepper motor speed controlled? State
  any two ways a program can do this. 2 points
• 5. For this problem, you should look at Figure 5A
  on the next page as a physical example of a
  stepper motor. It is an example of a stepper
  motor with four (4) magnetic windings which are
  connected via an interface circuit to the HCS12
  Port T pins 4, 5, 6, 7, with an armature
  (rotor) that has 12 poles (combined number of
  North and South magnetic poles). Notice how each
  step rotates the rotor 30 degrees, and notice the
  logic states on the Port T pins going from Step 1
  to Step 2. To rotate the rotor 90 degrees, you
  would need three (3) steps (see figure 5A for
  explanation).
• 6. Identify 2 major kinds of devices that can be
  used to interface a dc motor to the HCS12. 2
  points
• 7. Given that pulses need to be delivered to a
  specific dc motor at the rate of 12.5 kHz to
  avoid vibration, write down the C statements
  needed to output pulses from the HCS12 to drive
  the at 80 of its full drive level. 2 points
• 8. An HCS12 timer input capture/output compare
  register (TC0) holds the value 0x498 when timing
  the period between pulses coming in from a
  servomotors optical encoder (see Figure 8A below
  for setup of optical encoder). Assume the
  counter/timer is operating at

3

• 1.0us. The encoder wheel has 6 holes. Find the
  motors speed in RPM. Show work. 2 points
• 9. Unidirectional dc motors often have
  high-voltage diode connected for reverse-bias
  across the motors input terminals. Explain why
  this is done. 2 points
• 10. What advantages do dc motors offer over
  stepper motors? 2 points 
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