EC (Motion Control Devices) Ch 7

Question 1

What are the three basic classes of industrial limit switches?

Answer 1

Mechanical limit switches, Proximity switches, Rotary cam limit switches

Mechanical limit switches are activated by physical contact, proximity switches detect objects without contact, and rotary cam limit switches use rotating cams to control switching points.

Question 2

What is one use for the rotating-cam limit switch?

Answer 2

Used in hoists or cranes to control movement limits

For example, stopping upward motion when the hook reaches a set height.

Question 3

What are considerations when selecting a limit switch?

Answer 3

Operating voltage/current, Environmental conditions, Actuator type, Switching speed and frequency, Durability and life expectancy, Contact configuration

Each of these factors can significantly influence the performance and suitability of a limit switch.

Question 4

What is the difference between operating force and release force?

Answer 4

Operating force: The force required to activate the switch; Release force: The force at which the switch resets or deactivates

Understanding these forces is crucial for proper switch selection and application.

Question 5

Fill in the blank: Pretravel is the distance from rest to _______.

Answer 5

actuation point

Question 6

What is overtravel in relation to limit switches?

Answer 6

Additional movement after actuation before the stop

It refers to the distance the actuator moves beyond the actuation point.

Question 7

What is the accuracy and response time in a vane-type switch?

Answer 7

Accuracy: Moderate; Response time: Slower than solid-state switches

Accuracy is affected by air flow consistency and response time relies on vane movement and airflow.

Question 8

What are the basic symbols for mechanical limit switches?

Answer 8

NO contact, NC contact, Actuated NO, Actuated NC

These symbols represent different states of mechanical limit switches.

Question 9

Which methods are used for proximity switch operation?

Answer 9

Capacitive fields, Light rays

Capacitive proximity switches and photoelectric sensors utilize these methods, while low current input is not a sensing method.

Question 10

What determines the speed of response in proximity switches with oscillators?

Answer 10

Speed of the object, Oscillator frequency

The speed of the object and the frequency of the oscillator are critical factors affecting response time.