Automation - weeks 5/6 Flashcards
1
Q
define: digital
A
- device has only two states (eg. magnetic relays)
–> ON
–> OFF
2
Q
define: “digital logic”
A
- circuits using gates (solid-state control devices)
3
Q
what are 5 basic types of gates
A
- AND
- OR
- NOR
- NAND
- INVERTER
4
Q
what are 5 different types of logic
A
- RTL: resistor-transistor logic
- DTL: diode-transistor logic
- TTL: transistor-transistor logic
- HTL: high-transit logic
- CMOS: comes from COSMOS complementary, symmetry metal-oxide-semiconductor
5
Q
the AND gate may have ____ inputs, and ____ output
A
- may have several inputs
- only one output
6
Q
the AND gate must have all of its inputs _______ in order to get an output
A
- all of its inputs high
7
Q
the OR gate has ____ output when either or both of inputs are ____
A
- has high output when either or both of inputs are high
8
Q
the EXCLUSIVE OR gate has ____ output when _____ of its inputs are high
A
- high output when either, but not both, of its inputs are high
9
Q
the INVERTER has ____ input(s) and _____ output(s)
A
- one input
- one output
10
Q
with the INVERTER, the output is…
A
- inverted
11
Q
describe computer logic w the INVERTER
A
- circle drawn on gate means invert
12
Q
describe NEMA logic with the INVERTER
A
- X used to show gate is inverted
13
Q
what symbol is used for NOR gate
A
- same symbol for OR gate with an inverted output
14
Q
the NOR gate can be made by…
A
- connecting an INVERTER to output of an OR gate
15
Q
with the NOR gate, the output is _____ when any input is high
A
- output is zero (or low) when any input is high
16
Q
the NAND gate means…
A
- “NOT AND” gate
17
Q
what symbols are used for the NAND gate
A
- same symbols as AND gate w inverted outputs
18
Q
any input of a NAND gate is _____; output is _____
A
- input is low
- output is high
19
Q
describe the basic gate with the NAND gate
A
- can be used to make any other gates
20
Q
digital logic gates are generally houses in _____ pin, ____ packages
A
- 14 pin, IC packages
21
Q
what logic is frequently used in digital logic gates
A
- TTL logic, 7400 family
22
Q
with integrated circuits, what type of diagram is used when connecting or testing integrated circuits
A
- use a connecting diagram
23
Q
integrated circuits must be tested by _________, then testing ________
A
- must be tested by connecting power
- then testing inputs and outputs w special test equipment
24
Q
with integrated circuits, who determines which section of the circuit is not operating and replaces that module?
A
- electrician
25
why is a magnetic relay considered a digital device
- bc it only has 2 states: on or off
26
what are the 5 basic logic gates
- AND
- OR
- NOR
- NAND
- INVERTER
27
transistor-transistor logic operates on...
- 5 volts
28
- high transit logic operates on...
15 volts
29
most gate circuits are multi-input, ____ output devices
single
30
how many input & outputs does the inverter gate have
- 1 input, 1 output
31
when using TTL logic, 5 volts would indicate a high or low lvl
high
32
when using TTL logic, 0 volts would indicate a high or low lvl
low
33
when an inverter gate is used, is the input or output inverted
output
34
with an AND gate, if all inputs are high, the outputs are ____
high
35
with an OR gate, if one input is high, the output is ____
high
36
with a NOR gate, if one is high, the output is ____
low
37
with a NAND gate, if all inputs are high, the output is _____
low
38
a logic gate in which the output is always opposite the input is the...
- inverter
39
what symbol is used to represent "invert" when NEMA logic symbols are used?
X
40
what symbol is used to represent "invert" when computer logic symbols are used?
O
41
if an INVERTER is connected to the output of an NAND gate, what logic gate is formed
AND
42
if an INVERTER is connected to the output of an OR gate, what logic is formed
NOR
43
when using a two-input AND gate, what conditions of input must be met to have an output
- both inputs must be high
44
when using a two-input OR gate, what conditions of input must be met to have an output
- either input may be high
45
when using a two-input NAND gate, what conditions of input must be met to have an output
- either input may be low
46
when using a two-input NOR gate, what conditions of input must be met to have an output
- both inputs must be low
47
explain the difference between an OR gate and an EXCLUSIVE OR gate
- OR gate has high output when either or both inputs are high, exclusive has high output when either but not both inputs are high
48
integrated circuits can be tested with a:
a. volt meter
b. watt meter
c. ammeter
none of the above
49
the gate that is often referred to as the basic gate is...
NAND gate
50
digital circuit will be designed to perform same function as a ________ circuit
- common relay
51
a relay circuit is a ________ circuit with ______ protection
- a basic stop-start, push-button circuit w overload protection
52
with a start-stop push-button control, if the motor is overloaded what happens?
- too much current will flow thru circuit
53
with a start-stop push-button control, if current greater than normal flows through overload heater, what happens?
- the heater produces more heat than normal
54
with a start-stop push-button control, when the motor is overloaded, if current becomes high enough, it will cause what to happen?
- normally closed overload contact to open
55
with a start-stop push-button control, the overload contact is electrically isolated from??
- heater --> can be connected to different voltage source than motor
56
with a start-stop push-button control, what happens is the overload contact opens
- control circuit is broken
- relay de-energizes as if STOP button had been pushed
- after overload contact has been reset to normally closed position, coil will remain de-energized until START button is pressed again
57
see slides 10,11,12,13 --> dont know how to make cards on this bc i dont understand lol
...
58
with a start-stop push-button control, what happens when START button is pushed (6)
- a high is connected to input A or OR gate --> causes output of OR gate to change to high
- high output connected to input A of AND gate
- AND gate now has both of its inputs high
- input B of the OR gate becomes high also
- OR gate has a high connected to B input --> output will remain high when push button is returned to open condition and input A becomes low
- next, connect overload contact to circuit --> will cause output of circuit to turn off if it opens
59
slide 16 --> idk what they mean by previois circuit??
what are problems with previous circuit (3)
- if overload contact is reset, output will immediately change back to a high state
- if overload contact opens and is then reset in relay circuit, relay will not restart itself
- START button must be pushed to restart circuit (could become a safet6y hazard)
60
slide 18, also dont understand what they are referring to
other problems to be corrected
- gate could still assume either condition --> always connect inputs to definite high or low
- if resistor pulls an input low, gate will have a voltage drop at output --> push button can produce a high at input by adding an INVERTER
- circuit was used to control a 120 volt AC motor --> connect a solid state relay to output in place of LED
61
describe the purpose of analog sensing
- continuously varying
- designed to sense:
- voltage
- current
- speed
- pressure
- temp
- humidity
etc.
62
with analog sensing, a special module mounts on...
- I/O rack of PLC
63
with analog sensing, the analog sensory operates between...
- a range of settings
64
analog sensing is used to indicate...
- a range of values instead of operating in an on/off mode
65
pressure sensors can be constructed in several ways. describe the common method
- let pressure sensory operate current generator producing currents between 4 and 20 milliamperes
- sensory should produce a certain amt of current to eliminate voltage drop on lines
66
most analog sensors produce ______ signals. how much exactly?
- very weak
- 0 to 10 volts or 4 to 20 milliamperes
67
describe the installation of analog sensors in enviros w intense magnetic fields and large voltage spikes (2)
- easy to lose input signals in electrical noise
- special precautions should be taken when installing signal wiring between sensor and input module
68
describe installation of analog sensors (3)
- keep wire runs short
- plan signal cable route
- use shielded cable
69
describe grounding of analog sensors (2)
- not uncommon for different pieces of equipment to have ground lvls several volts apart
- large cable is sometimes used to tie two pieces of equipment together, forces them to exist at same potential
70
when grounding analog sensors, _______ method is not practical
- brute-force --> shield of signal cable is grounded at one end
71
what is the preferred method of grounding analog sensors
- to ground shield at the sensory
72
the differential amplifier is used to... (3)
- help overcome problem of induced noise
- detects voltage difference between pair of signal wires
- amplifies this difference
73
with differential amplifiers, since induced noise level should be same in both conductors, amplifier will _______ the noise
- ignore
74
if an analog sensor producing 50 millivolt signal, signal is applied to _______ but induced noise is at a lvl of ______ volts
- signal is applied to input module, but induced noise is at a lvl of 5 volts
75
with a differential amplifier, noise lvl is ____ times greater than signal lvl
- 100 times greater
76
with differential amplifier, induced noise lvl is _______ for both of input conductors
same
77
differential amplifier ignores ___ volt noise and amplifies only _____________
- ignores 5 volt noise
- amplified only voltage difference, 50 millivolts
78
what does analog mean
- continuously varying
79
what are analog inputs used to sense (6)
- voltage
- current
- speed
- pressure
- temp
- humidity
80
analog sensors are constructed to produce 2 types of output signals. what are the 2 types of signals, which is preferred and why?
- voltage and current
- current is preferred bc it eliminates the problem of voltage drop
81
would pushbuttons, float switches, and limit switches be considered analog devices
no
82
signal wires from a sensor to a controller should be run as _______ as possible so that the conductors are not exposed to surrounding magnetic fields
- short
83
when installing signal wires for analog sensors, what type of wire/cable should be used
shielded cable
84
what angle should signal wires cross power wires
90*
85
shielded cables are used to help prevent induced voltages caused by surrounding
- magnetic field
86
when deciding whether to use a 1-5 volt output sensor or a 4-20 mA output sensory what would be a major factor in the decision
- distance from the sensory to the controller
87
a controller is used to operate a modulating valve. if the controller has a 4-20 mA output and the valve is open 67%, the controller's mA output would be _____ mA
14.72 mA
88
a controller is used to operate a modulating valve. if the controller has a 1-5 volt output and the valve is open 67%, the controllers voltage output would be ___ volts
3.68 volts
89
the flow rate in a pipe needs to be monitored. a flow sensor with a 4-20 mA output is used as an input to a PLC. if the PLC was receiving a 9.45 mA current, what would the percentage of flow be
34%
90
the pressure in a chamber needs to be monitored. the pressure range is 0 to 90 PSI. a pressure sensory with a 1-10 voltage output as an input to a PLC. if the PLC was receiving 6.85 volts, what would the pressure in the chamber be?
58.5 PSI
91
when installing shielded cables for analog sensors, should the shield be grounded at both ends
- one end
92
what is the preferred location to ground the shield
- at the sensor
93
the first PLC was invented by... for use in the _____ industry
richard morley in 1969 for use in the auto industry
94
PLC processors still process info in which way?
- internally via gate logic (AND, OR, NAND, etc.) but they have been modified such that the PLC programs may be entered using conventional ladder logic
95
PLCs are very similar to which diagrams, making it user friendly
- similar to Line Diagrams
96
what are 5 basic parts of a PLC
- power supply
- CPU
- I/O section
- rack
- loader
97
what is the purpose of power supply
- supplies power for the CPU and the I/O logic
98
what is the purpose of the CPU
- acts as a computer
99
what is the purpose of the I/O section
- real world devices are wired to the modules
- inputs: push buttons, limit switches, etc.
- outputs: starter coils, solenoids, etc.
100
what is the purpose of the rack
- houses the power supply, CPU, and I/O sections
101
what is the purpose of the loader
- can be a laptop computer or a hand held computer
102
what are advantages of a PLC over conventional control (7)
- more internal relays & associated contacts to replace CR's, TR's, and counters
- flexibility of quick & easy changes, w little or no reqiring of I/O
- internal relays & contacts have no moving parts
- less cost & space required for initial installation and/or future modifications
- less cost due to reduced hardware, hard wiring, and associated down time requirements
- less device maintenance compared to other devices
- easy expansion of I/O capability
103
the National Eelectrical Manufacturing Association standards for programmable controllers recommend that consideration be given to:
- the use of emergency stop functions that are independent of the programmable controller
"when the operator is exposed to machinery, such as loading or unloading a machine tool, or where the machine cycles automatically, consideration should be given to the use of an electromechanical override or other redundant means, independent of the controller, for starting or interrupting the cycle"
104
the field wiring from electrical devices are terminated at the ________. they are designated to be either an _______ or _____ module
I/O modules
- input module
- output module
105
LED's visible on the PLS are used to indicate if an input or output is ________
on or off (high or low)
106
with I/O modules, the modules employ... what does this help do>
- opto-isolation to isolate the field wiring from the PLC circuitry
- this helps to eliminate damage caused by spiked and harmonics present on the line circuitry
107
some PLCs contain a ____ power source
DC power source
108
a DC power source can be used to...
- feed input devices
- if inputs are DC, correct polarities must be adhered to
109
module voltages range from...
5V DC to 240V AC/DC
110
input devices are categorized in two ways, what are they?
- discrete (digital)
- analog
111
digital/discrete inputs are recognized as... (2)
- ON or
- OFF
112
digital/discrete inputs are recognized as... (2)
- ON or
- OFF
113
if a doscrete device is connected to an input of a module, the module determines and communicates...
- the state of the limit switch to the processor
114
if the switch is open w discrete inputs, the module indicate....
- to the processor that the limit switch is OFF
- this condition is stored in the processor memory as a zero
115
with discrete inputs, if the swicth closes, the module will indicate to the processor that the limit switch is...
- ON
- the condition is then stored in the processor memory as a one (1)
116
with discrete inputs, all info stored in the processor memory about the status or condition of a discrete input device is always stored as a ______
1 or 0
117
describe how analog inputs work
- send a constant signal to a module
- the module then communicates the magnitude or strength of the signal to the processor
- the magnitude of voltage or current masy be used to represent some sort of condition
ex. a certain voltage might represent the speed of a motor (5 volts corresponds to 200 rpm, 10 volts to 400 rpm, etc.)
118
external relays (interposing relays)
*idk how to break this into smaller cards)
- larger solenoids, motor starter coils, and other heavier control loads occasionally draw a fair amt of current
- external relays are sometimes fed from outputs when currents or voltages are beyond the rating of the module output
- these interposing relays are used to switch the heavier control device
- the rating of PLC I/O is typically 5A/250V
119
Random Access Memory (RAM) is used to store __________. describe the ability to erase or change this
- PLC programs
- can be erased or changed over & over
120
Read-Only Memory (ROM) is used by the manufacturer to....
- store the operating system
121
can data written to a ROM be removed?
- cannot be removed, only read
122
both ROM and RAM styles of memory allow..... this means that RAM should be thought of as _____ RAM and ROM thought of as ____ RAM
- random access
- RAM = read-write RAM
- ROM = read-only RAM
123
Electrically Erasable Programmable Read-Only Memory is a special type of meory that can be erased by....
- exposing it to an electrical charge
124
Erasable Programmable Read-Only Memory (EPROM) can be erased by...
- exposing it to ultraviolet light
125
EPROM and EEPROM memory is used to store...
- PLC backup programs
126
integrated circuits (memory chips) used in the processor construction, can be separated into 2 distinct groups
- volatile
- non-volatile
127
what are volatile integrated circuits? what is an example?
- memory that loses its stored info when power is removed
- even a momentary loss of power will erase any info stored or programmed on a volatile integrated circuit
ex. RAM
128
what is non-volatile memory? what are examples
- memory that is able to retain stored info when power is removed accidentally or intentionally
ex. ROM, EEPROM, EPROM
129
what are backup batteries
- factory installed in various PLCs within either the power supply or the processor
130
backup batteries are used to protect...
- a PLCs volatile memory
131
all PLC batteries should be replaced every __ years
5
132
what are the 2 most common devices used to program a PLC
- laptop computers
- hand held units
133
are laptops or hand-held units more useful in troubleshooting and wide?
- laptops bc the view screen is larger = a large portion of program may be viewed at one time
134
the AND gate functions as ...
- 2 switches wired in a series
135
with an AND gate, ____ A and B must be ____ before the output can be hig
both, high
136
with OR gates, if ____ A or B is _______, the output will be high
- either, high
137
the OR gate functions as ....
2 switches wired in parallel
138
a NAND gate combines...
- a NOT gate with an AND gate
139
with a NAND gate, the output normally achieved from an AND gate is ....
- inverted
140
a NOR gate combines...
- a NOT gate and an OR gate
141
with a NOR gate, the output normally achieved from an OR gate is....
- inverted
142
the NOT gate is often referred to as an...
- inverted
143
a NOT gate has ___ input and ___ output
- 1 and 1
144
with a NOT gate, if the input is ______, then the output will be high
low
145
a PLC is normally programmed using....
- ladder logic
146
why is the use of ladder logic for a PLC a "wise choice"
- it closely resembles the way circuits are hard wired as per Line Diagram style schematics
147
what are 5 types of programming contacts
- examine on
- examine off
- force
- force off function
- force on function
148
with examine on, a N.O contact symbol is actually an ....
- an instruction --> telling the processor to look for an ON or (1) condition at the bit address (in the word) assigned to the N.O instruction
149
with examine on, if an ON condition exists...
- the instruction is said to be logically true
- this is similar to saying "if the contact closes, current may flow across the contact"
150
with examine off, a N.C contact symbol is an...
- instruction --> it tells the processor to look for an OFF or (0) condition at the bit address (in the word) assigned to the N.C instruction
151
with examine off, if an OFF condition esists, the instruction is said to be ....
- logically true
- this is similar to the saying "if the contact remains closed, current may flow across the contact"
152
what is force
- a mode of operation or instruction that allows the operator (as opposed to the processor) to control the state of an input or output device
153
what is force off function
- a feature that allows the user to change the state of any input or output by means of the programmer, independent of the PLC program
154
what is force on function
- a feature that allows the user to change the state of any input or output by means of the programmer, independent of the PLC program
155
Note: the force on and force off feature should never be used by personnel who do not completely understand the circuit and the process machinery or driven equipment. an understanding of the potential effect that forcing a given contact or coil has on machine operation is essential if hazardous or destructive operation is to be avoided
156
a ladder diagram should be read...
- left to right and from top to bottom
157
in ladder diagrams, the vertical circuitry lines, known as rails, represent...
- the voltage potential of the control circuit
158
with ladder diagrams, the potential may vary anywhere from...
6V to 600 V AC or DC
159
with ladder diagrams, standard labeling of the rails that represent an AC source is..... that represent a DC source is...
L1 and L2 represent an AC source
+ and - represent a DC source
160
the rails of a ladder diagram may be marked X1 and X2 (N) when the....
- voltage potential is supplied by a grounded transformer
161
with a ladder diagram, the horizontal lines that connect to the rails are generally referred to as...
- rungs
162
with ladder diagrams, it is good practice to show all devices or components in order of....
- importance
163
with ladder diagrams, when is a stop button shown in comparison to a sgtart button
- a stop button is almost always shown before a start button
164
with ladder diagrams, electrical devices or components are shown in their ______ condition
- normal condition
165
what is the normal condition of electrical diagrams
- is the de-energized (OFF) condition with no external forces such as pressure or flow acting on any of the devices
166
before installing the rack or chassis, consideration must be given to the enviro it will be housed in (6)
- temp
- dust
- vibration
- humidity
- electrical disturbances from electrical equipment and wiring
- trouble shooting accessibility
167
the ambient temp of the PLC location should never be lower than ____ or higher than ____
- lower than 0*C
- or higher than 32*C
168
describe the process of convection
- fans may not be supplied w I/O racks, cooling may be accomplished by heat from water components rising and drawing cool air in through the bottom of the rack = result is constant mvmt of air
169
what should be considered for controlling the temp of the enclosure housing the PLC
- consideration should be given to the use of cabinet cooling fans and heaters
170
what happens if dust is permitted to accumulate within processors, power supplies, and I/O modules
- it will prevent effective heat dissipation of electronic components
171
due to unwanted PLC system failures, it is important for enclosures housing PLC racks to be ..... r.t dust
- to be both dust tight & big enough to allow for ample air circulation for heat dissipation
- installation manuals will usually include minimum size enclosure specifications
172
excessive vibration can lead to...
- early component failure
173
due to the negative effects of excessive vibration, it is important to mount PLC equipment on..
- solid, non-vibrating surfaces
174
vibration effects from equipment must be minimized to assure...
- longevity of the equipment
175
humidity, while normally not a problem, must be considered when installing a PLC. Why?
- exposing electronic equipment to high humidity lvls over an extended period of time can reduce component life and affect the operation
176
while it is commonly useful for PLC's and programming devices to be installed in central locations such as control centers, the use of remote I/O racks allows...
- inputs and outputs modules to be installed at the same location as the equipment being controlled
177
the risk of a line disturbance occurring ______ as the wire length between the processor and the remote rack increases
increases
178
the decimal system uses ___ unique numbers, which are __ thru __
- uses 10 unique digits, 0 thru 9
179
a numbering system that uses 10 digits is said to have a base of ___
10
180
the binary system uses __ digits, what are they
- 2 digits, 1 and 0
181
the binary system has a base of ___
2
182
like the decimal system, in the binary system each digit has a certain...
- place value
183
describe the place values in the binary system
- the first place to the left of the starting point is the units or 1s location (260)
- the next place, to the left of the units place, is the 2s place, or base 2^1
- the next place value is the 4s, or 2^2
- then 8s, or base 2^3 and so on
184
the octal system is made up of __ digits, which numbers?
- 8 digits, 0 thru 7
185
describe the place values in the octal system
- first digit to the left of the octal point is the units place, or 1s, and has a base or power of 8^0
- the nexgt place is the 8s or base 8^1
- the next place is 64s or base 8^2
- followed by 512s, or base 8^3
- then 4096s or base 8^4 and so on
186
the hexadecimal system has ___ digits, what numbers are used?
- 16 digits
- 0 thru 9, then A, B, C, D, E, and F
- next group is: 10,11,12,13,14,15,16,17,18,19,1A,1B,1C,1D,1E,1F
187
describe the place values in the hexadecimal system
- 1's-16^0
- 16's - 16^1
- 256's - 16^2
- 4096 - 16^3
- 65536's - 164 and so on
188
the binary coded decimal system uses the decimal numbers
0 thru 9
- the decimal numbers are individually converted to their binary equivalents , the binary numbers can then be deposited into words rather easily
