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Machine Control Programming > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

original purpose of PLC

A

replace electromagnetic relays with a solid state switching system that could be programmed

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2
Q

electrical relay

A

magnetic switch that uses electromagnetism to switch contacts

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3
Q

relays

A
  • control relay

- motor starter

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4
Q

contactor

A

special type of relay designed to handle heavy power loads

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5
Q

motor starter

A

designed to provide power to motors, made up of a contactor with an overload relay

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6
Q

overload relays

A
  • designed to meet special protective needs of motor control circuit
  • allow harmless temporary overloads that occur when a motor starts
  • will trip/disconnect power if overload persists
  • can be reset
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7
Q

manually operated switches

A
  • controlled by hand

- examples: toggle switches, push buttons, knife switches, selector switches

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8
Q

dual in-line package switches

A
  • small switch assemblies designed for mounting on printed circuit board modules
  • use on/off settings to set parameters
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9
Q

mechanically operated switch

A

controlled automatically by factors such as pressure, position, or temperature

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10
Q

level switches

A

used to sense liquid levels in vessels and provide automatic control for motors

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11
Q

proximity switches

A

detect presence of object without physical contact

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12
Q

inductive proximity switch

A

used to detect both ferrous metals (iron) and nonferrous metals

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13
Q

capacitive proximity sensors

A

produce electrostatic field instead of electromagnetic and are actuated by both conductive/nonconductive materials

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14
Q

magnetic reed switch

A

when a magnetic field is created, the ends of the two reeds in a glass tube are attracted to one another and actuate the switch, they are unaffected by dust/humidity/fumes

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15
Q

photovoltaic cell

A

light produces voltage

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16
Q

photoconductive cell

A

light changes resistance

17
Q

photoelectric sensor

A
  • detect light beam and respond to change in received light intensity
  • has receiver and transmitter
18
Q

scan technique of photoelectric sensor

A
  • through beam scan (direct): transmitter/receiver directly in line with one another
  • retroreflective: transmitter mounted on top with receiver on bottom and reflective tape allows the beam to go from transmitter to receiver
19
Q

fiber optic sensors

A

use flexible cable containing tiny fibers that channel light from emitter to receiver, immune to electrical interference

20
Q

bar code sensors

A

light source illuminates bar code symbol, bars absorb light and space reflects it, photodetector collects light in form of pattern, decoder converts data

21
Q

ultrasonic sensor

A

sends high frequency sound waves toward target and measuring time it takes for pulses to bounce back, can detect solids/fluids

22
Q

strain gauge

A

converts mechanical strain into an electric signal

23
Q

strain gauge load cell

A

usually made with steel and sensitive strain gauges

24
Q

most widely used temperature sensor

A

thermocouple

25
Q

how do thermocouples work

A

when 2 dissimilar metals are joined, a predictable DC voltage will be generated that relates to the difference in temperature between the hot and cold junctions

26
Q

resistance temperature detectors

A

the hotter they become, the higher the value of the electrical resistance

27
Q

turbine type flowmeters

A

higher the flow rate means the faster the turbine will rotate

28
Q

tachometer

A

convenient for converting rotational speed into analog voltage signal

29
Q

encoder

A

convert linear or rotary motion into binary digital signal

30
Q

actuator

A

any device that converts electrical signal into mechanical movement

31
Q

stepper motors

A

rotates in discrete increments when electrical command pulses are applied

32
Q

open loop vs closed loop system

A

-open loop is control without feedback

33
Q

seal in (holding) circuits

A

method of maintaining current flow after momentary switch has been pressed and released

34
Q

latching relays (latching and unlatching)

A
  • designed to hold relay closed after power has been removed from coil
  • both must have same address

Machine Control Programming (12 decks)

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