Supplement to Chapter 02 - Input/Output Devices

1. Chapter 02
Supplement and reinforcement of
Input Devices and Output Actuators

2. I/O Devices
 I/O can be categorized into three areas or types:
 Binary (Discrete) (Unfortunately to add some confusion they are
also referred to as Digital)
 This includes all mechanical switches such as: pushbuttons,
selectors, limit (micro), motor starter aux. contacts, relay
contacts, etc.
 It also includes all solid state sensors such as: photoelectric,
inductive and capacitive proximity, etc.
 Digital
 This includes: processed video, charge coupled devices
(CCD) arrays, inductive coil impulse generators, optical code
wheels (encoders), etc.
 Analog
 This includes: potentiometers, linear variable differential
transformers (LVDT), video correlation, pressure,
temperature, flow, strain, etc.

3. I/O Details
 Mechanically operated switches are mode up of:
 Pole (sometimes referred to as a wiper)
 Contact
 Actuator
Pole or
Wiper
Pole or
Wiper
Contact
Contact
Contact
SPST Switch
SPDT Relay
SPSTDB Switch
Single Pole Single Throw
Double Break
Pole or
Wiper
Contacts
SPDTDB Switch
Single Pole Double Throw
Double Break
Pole or
Wiper
Contacts
Contacts

4. Mechanical Switches
Normally Open Normally Closed
Normally Open
Normally Closed
Push Buttons
Selectors
Limit (micro)

5. Mechanical Switches
Normally Open
Normally Closed
Normally Open
Normally Closed
Normally Open
Normally Closed
Normally Open
Normally Closed
Normally Open
Normally Closed
FLOAT SWITCH PRESSURE SWITCH TEMPERATURE SWITCH
FLOW SWITCH FOOT SWITCH

6. Relays
Electro-Mechanical
NC
NO
NC
NO
POLE
POLE
NO NC

7. Switch Bounce
 Switch contact bounce
Ø V
+V
+V
PLC
Input

8.  Switch contact bounce
Switch Bounce
Ø V
+V
+V
PLC
Input
Switch
Closes
Switch
comes to
rest
Random
‘Bounce’

9. Actual Switch Bounce

10. Sensors
Photoelectric, Inductive and Capacitive

11. Sensing Theory Primer
 Sensors provide the equivalence of eyes, ears, nose and tongue to
the microprocessor of a PLC/PAC or computer.
Microprocessor
Optical
sensor
Gas
sensor
Microphone
Probe
Graphic from: Petruzella, Frank D. (2005). Programmable Logic Controllers (3rd ed.). New York, NY: McGraw-Hill

12. Review of Basic Solid
State Devices
 Brief review of:
 Diodes
 Multiple uses within PLC/PAC control circuits
 DC flyback protection (Inductive surge suppression
for DC inductive loads)
 Transistors
 Commonly used in PLC/PAC DCV output modules
 Silicon Controlled Rectifiers (SCR)
 Triac
 Commonly used in PLC/PAC ACV output modules

13. Diode
 Current flow in one direction only.
CathodeAnode
Direction of
Conventional Current

14. Forward Bias
 A diode will conduct current when the anode is
0.7V more positive than the cathode. When
current is flowing the diode is Forward Biased.
+
Direction of
Current Flow
+

15. Reverse Bias
 A diode will not conduct current when the anode
is not 0.7V more positive than the cathode.
When current is not flowing the diode is Reverse
Biased.
NO CURRENT FLOW
++

16. Transistor
 Transistors are commonly used as the switching device
in PLC/PAC DCV output modules. Just like a diode, a
0.7V bias is required for current flow.
 Transistors are available in two polarities, NPN & PNP.
 NPN  Sink
 PNP  Source
NPN PNP
+
+
+
+
+
+
Emitter Emitter
Base Base
Collector Collector

17. Field Effect Transistors
 Field Effect Transistors (FETs) can also be
used as switches.
 Transistors are current operated devices
and FETs are voltage operated devices.
http://www.talkingelectronics.com/projects/MOSFET/MOSFET.html

18. SCR and Triac
 SCRs can be used in ACV output modules but Triacs are
more commonly used as the switching device in
PLC/PAC ACV output modules
Gate
Cathode
Anode
Gate
Main Terminal 1
Main Terminal 2
SCR Triac

19. SCR and Triac Usage
Review
 One of the many applications for SCRs and Triacs is for
light dimming and simple motor control. They are also
used as AC voltage switches.
 A Triac in its basic form is nothing more than two SCRs
in parallel, back-to-back, with their gates connected
together.


20. SCR Usage – Light
Dimmer
 Representation of a lamp dimmer circuit using
an SCR.
 An SCR will only conduct on one half of the sine
wave.
ACV
Zero Crossing
Detector
Adj. Firing
Angle

21. SCR Usage Review
 Waveforms across the lamp at different firing angles.
 Firing at different angles changes the effective AC
voltage across the lamp (load).
Fired at 30° Fired at 90°
Fired at 135°

22. Triac Usage – Light
Dimmer
 Representation of a lamp dimmer circuit using a
Triac.
 A Triac will conduct on both halves of the sine
wave.
ACV
Zero Crossing
Detector
Adj. Firing
Angle

23. Triac Usage Review
 Waveforms across the lamp at different firing angles.
 Firing at different angles changes the effective AC
voltage across the lamp (load).
Fired at 30° Fired at 90°
Fired at 135°

24. AC Effective Voltage (FYI)
 SCRs and Triacs change the effective voltage seen by a
load.
 Power calculations based upon a voltage midway
between one peak and zero are not correct because AC
voltage generally changes sinusoidal from zero to peak,
rather than linearly as in DCV.
 The voltage value that gives the correct result is called
the Effective Voltage because it has the same effect on a
power calculation as does a DC voltage of the same
value.
 Effective Voltage is equal to the square root of the mean
value of the squares of all the instantaneous values of an
AC voltage. Because of that, Effective Voltage is also
known as the Root Mean Square or RMS Voltage.

25. AC Voltmeters (FYI)
 AC voltmeters read the AC voltage in one of three ways:
 Average
 Root Mean Square (RMS)
 True RMS
 Average responding voltmeters simply use a diode to rectify the AC
signal being measured and read the equivalent DC voltage. Most
VOMs use this method for ACV measurements. (Not very accurate
on non-sinusoidal waveforms).
 RMS voltage is a function of power and an RMS meter uses
electronics to simulate an AC power measurement making the ACV
measurement more accurate.
 True RMS voltage is also a function of power but also takes into
consideration the heating characteristics of the ACV. True RMS
voltmeters use a sophisticated µP based calculation that will mimic a
bolometer by calculating the area under the curve. This is the most
accurate of ACV measurements. This measurement will include any
spikes or distortion on the AC signal.
 Fairly good source to learn more about measuring AC voltage:
http://www.allaboutcircuits.com/vol_2/chpt_1/3.html

26. Inductive Flyback and
Protecting the PLC/PAC
+Vac+Vdc

27. Photoelectric Sensing
 Photoelectric Sensor
 An electrical device that responds to a change in the intensity of
the light falling upon it.
 Photocell
 A photocell is a device that changes resistance when it is
exposed to light. This change in resistance can then be detected
to trigger a response. The earliest method of photoelectric
sensing used a photocell to sense light change.
 Non-modulated
 The earliest photo sensors consisted of an incandescent light
bulb and a photocell.
 The gain of the non-modulated sensor is limited to the point at
which the receiver recognizes ambient light.
 This type of sensor is only powerful if its receiver can be made to
see only the light from its light source (emitter).
 What are some advantages and disadvantages to this type of
sensor?

28. Ambient Light Receiver
 Ambient light receivers are non-modulated type
photoelectric sensors that are still in frequent
use.
 Applications for such devices could be:
 Detecting red-hot metal or glass that emit large
amounts of infrared light.
 As long as these materials emit more light than the
surrounding light level, ambient light receivers can reliably
detect these materials.
 A sensor mounted under an open frame conveyor
that is reading the ambient light in the room.
 If a box, carton or some other material passes along the
conveyor and over the sensor, it blocks the ambient light
from the sensor. This change in light is used to detect the
presence of an object on the conveyor.

29. Light Sources (Emitters)
 Light Emitting Diode (LED)
 A solid state device electrically similar to the diode
except that it emits a small amount of light when it is
forward biased.
RED GREEN AMBER
BLUE INFRARED

30. Light Sensor (Receiver)
 Phototransistor
 A solid state device similar to a transistor except that
the base connection is made using light. These
devices are widely used as photoelectric receivers.
Phototransistor

31. Picture borrowed from the Banner Photoelectric Handbook
Modulated LED Sensors
 LEDs can be turned on-
and-off at frequencies
typically in the kilohertz
(KHz) range. This switching
on-and-off is referred to as
modulating the light.
 The receiver can be tuned
to this frequency so that it
only sees the light signals
that pulse at this frequency.
 This is what gives the LED
sensor its apparent power.
Picture borrowed from the Banner Photoelectric Handbook

32. Photoelectric Sensing
Modes
 Opposed Mode
 Retroreflective Mode
 Proximity Mode
 Diffused mode
 Divergent mode
 Convergent Beam mode
 Fixed-field (sometimes called background
suppression mode)
 Adjustable-field

33. Opposed Mode Sensing
Picture borrowed from the Banner Photoelectric Handbook
Receiver
Emitter
The emitter
is a light
source
Object
 Often referred to as
“Direct Scanning” or
“Break Beam” mode.
 In this mode the
emitter and receiver
are positioned
opposite each other
so that the light from
the emitter is aimed
at the receiver.
 An object is detected
when it interrupts the
“effective beam” of
light between the two
sensing components.

34. Effective Beam
 Photoelectric sensors will sense a change in
light when the effective beam is completely
blocked.
Effective Beam
Radiation Pattern
Field of View
Emitter Receiver

35. Shaping the Effective
Beam
 The effective beam can be shaped by using
different sized lenses on the emitter and/or
receiver.
Effective Beam is:
Cone Shaped
Emitter (or receiver)
with large lens
Emitter (or receiver)
with small lens

36. Shaping the Effective
Beam
 Apertures can also be placed on the lenses to shape the
effective beam for sensing small objects that would not
normally be large enough to break the effective beam.
Picture borrowed from the Banner Photoelectric Handbook

37. Retroreflective Mode
 This mode is also called
“reflex” mode or simply
“retro” mode.
 The emitter and receiver
circuitry of these sensors
are in the same package.
 The light beam is
established between the
emitter, a retroreflective
target and the receiver.
 Just as in opposed mode
sensing an object is
sensed when it breaks
the effective beam.
Retro Target
Object
Picture borrowed from the Banner Photoelectric Handbook

38. Retroreflective Mode
 The range of a
retroreflective sensor is
defined as the distance
from the sensor to its
retroreflective target.
 The effective beam is
usually cone-shaped and
connects the periphery of
the retro sensor lens to
that of the retroreflective
target.
 A good reflector will
return 3,000 times as
much light as a piece of
white paper. This is one
of the reasons that a
retroreflective sensor will
only recognize the light
coming from its emitter.
Retroreflective
Sensor
Radiation pattern
and field of view
Effective Beam
Retroreflective
target
Picture borrowed from the Banner Photoelectric Handbook

39. Retroreflective Mode –
Sensing Shiny Objects
 Shiny objects can pass through a retroreflective beam.
To cure this problem the sensor and reflector can be
mounted to “skew” the light away from the shiny object.
Only 10º to 15° is required to be effective.
Boxes with shiny
Vinyl wrap
Conveyor
Retro target
Skew angle >10°
Reflected
Light
Retroreflective
Sensor
>10°
Flow
Picture borrowed from the Banner Photoelectric Handbook

40. Retroreflective Mode –
Sensing Shiny Objects
 It becomes more complicated if the shiny surface is a rounded
surface where light can be reflected at unpredictable angles.
 Position the sensor so that the light beam strikes the object at both a
vertical and horizontal skew angle.
Picture borrowed from the Banner Photoelectric Handbook
Retroreflective target mounted
at angle, parallel to sensor lens
Retroreflective sensor mounted at vertical
and horizontal angle to the direction of flow
Shiny object with
radii
Flow
Tilt up or down
and
Rotate right or left
Emitted
Light

41. Retroreflective Mode –
Sensing Shiny Objects
 Polarizing or anti-glare filters can also be used to reduce
the proxing effect on shiny objects.
Emitted Light is
linearly polarized
Shiny Object
Retroreflector
Light waves that are reflected by shiny surface
are in phase with the emitted light and are
blocked by the receiver filter
Retroreflected light waves are rotated 90° by the
corner-cube reflector and will pass through the
filter to the receiver
Picture borrowed from the Banner Photoelectric Handbook

42. Proximity Mode Sensing
 Proximity mode involves detecting an object that
is directly in front of the sensor by detecting the
sensors own emitted energy reflecting back from
the objects surface.
 There are five proxing modes:
 Diffused
 Divergent
 Convergent
 Fixed field (background suppression)
 Adjustable field

43. Diffused Sensing Mode
 This is the most
commonly used
photoelectric sensing
mode.
 In this mode, the
emitted light strikes the
surface of the object
being sensed at some
arbitrary angle.
 The light is then
diffused from the
surface at many angles.
 The receiver uses a
lens, whereby it can be
at some arbitrary angle
and still receive a small
portion of the diffused
light.
Emitted Light
Received Light
Object
Picture borrowed from the Banner Photoelectric Handbook

44. Divergent Sensing Mode
 This is a special
short range mode
that does not use
any lens in an effort
to avoid signal loss
from shiny objects.
 By eliminating the
collimating lens, the
sensing range is
shortened but the
sensor is also made
less dependent
upon the angle of
incidence of its light
to the shiny surface.
Picture borrowed from the Banner Photoelectric Handbook
Object

45. Convergent Beam Sense
Mode
 This mode is very effective for
sensing small objects.
 They use a lens system to focus
the emitted light to an exact point
in front of the sensor and also to
focus the receiver to this same
point producing a small, intense,
well-defined sensing area at a
fixed distance from the lens.
Depth of Field
Focal Point
Convergent
Beam
Sensor
Picture borrowed from the Banner Photoelectric Handbook

46. Laser Diode Convergent
Sensor
 This type of sensor
produces an extremely
small, concentrated focal
point.
 The focal point can be in
the order of 0.25mm (0.01”)
in diameter at a sensing
distance of 100mm (4.0”).
 The narrow, sharply-
defined beam of a laser
diode can detect the edge
of a semiconductor wafer
(775m or 0.03 in.) in a
wafer cassette mapping
application. (A
representation is shown
here).
Picture borrowed from the Banner Photoelectric Handbook

47. Fixed-Field (Background
Suppression)
 Fixed-field mode has a definite limit to its
sensing range. They ignore objects beyond their
sensing range regardless of the objects surface
reflectivity.
 Fixed-field sensors compare the amount of
reflected light seen by two differently-aimed
receivers, R1 and R2. A target is recognized as
long as the amount of light reaching R2 is
greater than or equal to the amount of light
reaching R1.
 A depiction of a fixed-field mode sensor is
shown on the next slide.

48. Fixed-Field (Background
Suppression)
Picture borrowed from the Banner Photoelectric Handbook
Lenses
Object A Object B
Emitter
Receiver
Maximum Sensing Distance
Minimum
Sensing
Distance
Fixed
Sensing
Field
Senses when light received by R2 ≥ the light received by R1

49. Adjustable Field Mode
 Similar to fixed-field,
adjustable field sensors
can distinguish between
objects that are various
distances from the sensor.
 The receiver produces
two currents; I1 and I2.
The ratio of the current
changes as the received
light signal moves along
the length of the receiver
element.
 The sensing cutoff
distance is directly related
to the ratio of the two
currents which are
adjustable using either
electronic or mechanical
adjustments.
Picture borrowed from the Banner Photoelectric Handbook

50. Sensor Adjustments
 Photoelectric sensors need to be properly aligned with
the target whether it is a reflector or the object being
sensed. The alignment is usually accomplished by
mechanically orienting the sensor and/or the target.
 Some sensors have “sensitivity” adjustments to adjust
the “gain” of the sensor. This adjustment is made such
that the sensors output ‘just’ turns on/off when the object
to be sensed is within the sensing range.
 Excessive gain is a measurement that may be used to
predict the reliability of any sensing system. It is the
measurement of the sensing energy falling onto the
receiver element of a sensing system over and above
the minimum amount required to just operate the
sensors amplifier.

51. Sensor Output Operating
Modes
 Light Operated
 The sensor output will energize (turn ON)
when the receiver sees light.
 Dark Operated
 The sensor output will energize (turn ON)
when the receiver sees an absence of light
(darkness).

52. Sensor Response Time
 The response time of a sensor is the maximum
amount of time required for the sensor to
respond to a change in the input signal (sensing
event). It is the time between the leading or
trailing edge of a sensing event and the change
in the sensors output.
 Response time can be calculated and will be
different depending upon the type of object
being sensed and how the object is moving
(axial, radial direction or rotary).
 The formulas for calculating the response time
can be found in the manufacturers specification
sheets or in the manufacturers product catalog.

53. Training Panel Opposed Mode
Sensors
 Make adjustments to the photoelectric sensors
on the PLC/PAC training panel.
 Banner Engineering
http://www.bannerengineering.com/en-US/
 SM31E & SM31R
http://www.bannerengineering.com/en-US/support/partref/25623
 Data Sheet
http://info.bannerengineering.com/xpedio/groups/public/documents/literature/03560.pdf
 Installation Guide
http://info.bannerengineering.com/xpedio/groups/public/documents/literature/69943.pdf

54. Training Panel Fiber Optic
Sensors
 Use the Internet and look up the specifications and data
sheets for the fiber optic sensor.
 There are two parts to this sensor, look up both parts
 Sensor body
 Power block
 Read through the data sheets and attempt making some
of the adjustments. (The sensors on the training panel are fairly “beat-
up” from use, so don’t get frustrated if the adjustments do not work perfectly).
 When you are finished, the sensor should be “ON” when
the motor wand is present and “OFF” when it’s not
present and the alarm output should be “ON (N/C)”
unless an alarm condition exists.
 When you are finished, make sure all the sensors have
their covers reinstalled and the fiber optic sensor is in
“Light Mode” and the opposed mode sensors are in
“Dark Mode”.

55. Inductive Proximity
Sensors
 Inductive proximity sensors are used to sense
metal objects.
 The sensing distance is usually specified in
millimeters and varies with the size of the sensor.
The smaller the sensor, the closer the object to be
sensed must get to the sensor. As the sensor gets
larger the object sensing distance becomes further.
 Operationally they are solid state devices with no
moving parts. They consist of a:
 coil
 high-frequency oscillator
 detector circuit
 solid state output

56. Inductive Proximity
Sensors
 Operationally, a high-frequency field is generated in a coil mounted in
the nose of the sensor and directed from the sensing surface of the
sensor.
 When a metal object enters the high-frequency field, eddy currents are
induced into the surface of the target object.
 These eddy currents cause a lose of energy in the high-frequency
oscillator to occur and the amplitude of the oscillator reduces.
 The detector circuit detects the reduction in amplitude of the oscillator
and energizes the output circuitry to turn the sensor ON.
Oscillator Detector Output
Target

57. Inductive Prox. Sensor –
Shielded vs. Non-Shielded
 Shielded sensor construction includes a metal band that
surrounds the ferrite core and coil of the sensor. The band
helps to bundle or direct the electro-magnetic field to the
front of the sensor.
 Non-shielded sensors do not have this metal band and
therefore can be sensitive to sensing objects on the sides of
the sensor.
 Shielded sensors can be safely mounted in metal panels or
metal brackets whereas non-shielded sensors require a
metal free area around the face of the sensor.
 Spacing of adjacent or opposing sensors must be taken into
consideration due to the possible interference of the electro-
magnetic fields generated. To avoid this problem always
leave at least 2-sensor diameters, center-to-center, between
adjacent or opposing sensors.

58. Mounting Inductive
Proxs.
When mounting inductive prox.
Sensor side-by-side or face-to-face,
there needs to be at least two
sensor diameters between them so
that the magnetic field emanating
from the sensors do not interfere
with each other causing the
possibility of the sensors being ON
all the time.

59. Inductive Prox. Sensor –
Sensing range
 The normal sensing range of the
different sensors is basically a
function of the diameter of the
sensing area or sensing coil. The
shape of the target and the alloy
of the metal will also affect the
actual operating range.
 Correction factors need to be
applied to non-ferrous targets
and are nominal values.
 The table below lists some of
these correction factors.
Sensing range multipliers Shielded Non-Shielded
Aluminum (foil) approx. 1.00 1.00
Stainless steel (alloy dependent) 0.35 to 0.65 0.50 to 0.90
Brass 0.40 0.55
Aluminum (massive) 0.30 0.55
Copper 0.25 0.45

60. Hysteresis
 Hysteresis is the distance between the operating
points of an inductive proximity sensor when the
target is approaching the face of the sensor and
the release point when the target is moving
away from the sensor.
 As the target approaches the sensor it must
always get closer to the sensor to make the
sensor turn ON then to make it turn OFF when it
is moving away from the sensor.
 The following slide demonstrate the hysteresis.

61. Hysteresis – Axial
approach
 When the target
approaches the
sensor in an axial
manner the sensor
will turn ON when
the target reaches
the sensors
prescribed sensing
distance.
 When the target is
leaving the sensor
the target must be
moved further away
from the sensor then
the prescribed
sensing distance for
the sensor to turn
OFF.
TargetAxial approach
Switch point when leaving
Sensor turns OFF
Switch point
when approaching
Sensor turns ON

62. Hysteresis – Radial
approach
 When the
target
approaches the
sensor in a
radial manner
the target must
move further in
front of the
sensor to turn it
ON than it has
to move away
from the
sensor to make
the sensor turn
OFF.
Target
Radial approach
Sensor ON when target approaches
Sensor OFF when target leaves

63. Capacitive Sensors
 Capacitive sensors will sense any object that gets within
their sensing range.
 They can sense paper, wood, metal, liquid, powders, etc.
 They are one of the few sensors that are approved by
the Food and Drug Administration (FDA) to come into
direct contact with consumable food products.
Oscillator Detector Output
Target
A
C
C
B
B
C
B
A
Front View

64. Capacitive Sensors
 The active element is formed by two metallic electrodes positioned much
like an “opened” capacitor.
 Electrodes A and B are placed in a feedback loop of a high frequency
oscillator.
 When no target is present, the sensors capacitance is low making the
oscillator amplitude small.
 When a target approaches the face of the sensor, the capacitance
increases resulting in an increase in amplitude of the oscillator.
 This amplitude increase is detected by the detector and output of the sensor
is turned ON or OFF.
Oscillator Detector Output
Target
A
C
C
B
B
C
B
A
Front View

65. Capacitive Sensors
 Capacitive sensors have a compensation adjustment.
 Electrode C is the compensation electrode.
 The adjustment can null the affect of water droplets, humidity, dust,
etc. from affecting the operation of the sensor.
 In practice the compensation can literally be adjusted to “see
through” objects to another object. As an example, the sensor could
be adjusted to read the ink in a felt tip pen after the cap has been
placed on the pen. (Actual process at Crayola)
Oscillator Detector Output
Target
A
C
C
B
B
C
B
A
Front View

66. Sensor Connections
 Sensors come in many connection
configurations. Always read the manufacturer
wiring specifications before connecting a sensor.
Listed are the three most common
configurations:
 4-wire Sink or Source
 Some of these sensors can be wired as either sink or source.
Not all 4-wire sensors can be wired in either polarity. Some
4-wire sensors can offer NO and NC operation and/or an
alarm output, etc.
 3-wire Sink or Source
 These sensors are specified as either sink or source when
they are purchased. The polarity can not be changed.
 2-wire Sink or Source
 These sensors can be wired as either sink or source and are
becoming very popular because of their simplicity.

67. Sensor Connections
 Sensor connections vary not only between
manufacturers, but within the same
manufacturer. Always read the manufacturers
wiring specifications before connecting a sensor
into the circuit.
 Wire color coding is sometimes used to identify
the sensor connections. The two wires that are
most in common across manufacturers are the
power connections. Remember…sensors are
solid state devices and therefore require power
to operate.
 Brown wire – +VDC usually 24VDC
 Blue wire – VDC common

68. Interpreting Sensor Wiring
Diagrams
 These wiring
diagrams are from the
Turck sensor catalog
for one particular 3-
wire inductive
proximity sensor.
 Note how the polarity
is designated.
 Sink sensors supply
the VDC common to
the load when the
switch is closed.
 Source sensors
supply the +VDC to
the load when the
switch is closed.
 The load in our case
would be the PLC
input module.
NPN (Sinking)
PNP (Sourcing)

69. Interpreting Sensor Wiring
Diagrams
 This is a wiring
diagram from
the Turck sensor
catalog for one
particular 2-wire
inductive
proximity
sensor.
 Note how the
polarity is
designated.
 Two wire
sensors can be
wired as sink or
source.

70. Interpreting Sensor Wiring
Diagrams
 These wiring diagrams
are from the Turck
sensor catalog for one
particular 4-wire
inductive proximity
sensor.
 Note how the polarity is
designated.
 This sensor has one
pole, a normally open
(N.O.) and a normally
closed (N.C.) contact.
(SPDT)
NPN (Sinking)
PNP (Sourcing)

71. Interpreting Sensor Wiring
Diagrams
 These wiring
diagrams are from
the Turck sensor
catalog for one
particular 4-wire
inductive proximity
sensor.
 Note how the
polarity is
designated.
 This sensor have
one pole, a
normally open
(N.O.) and normally
closed (N.C.)
contact. (SPDT)
NPN (Sinking)
PNP (Sourcing)

72. Interpreting Sensor Wiring
Diagrams
 This wiring diagram is from the Banner Engineering
manual for a particular 4-wire sensor.
 This sensor is Bipolar, meaning that a sink or source
load can be switched depending upon which lead, the
white or black, that is connected to the load.
 White – Sink connection
 Black – Source connection

73. Interpreting Sensor Wiring
Diagrams
 These
diagrams
are of a
Keyence
photo –
electric
sensor.
 This is an
example of
why the
manf. data
sheets are
required.

74. I/O MODULES ARE AVAILABLE IN MANY DIFFERENT
CONFIGURATIONS
PLC/PAC Module Wiring

75. I/O Module Wiring
 PLC/PAC I/O modules are available in many
different wiring configurations:
 The entire module is either sink or source and
uses one I/O power source.
 The module is split in two halves where one half
can be sink and the other half can be source or
both halves can be sink or source. When used
split, two different I/O power sources can be
used.
 The module is split into more than two halves
where each section can be independent from the
others or can be combined into one section.

76. Single Section Module
This is module is a
single section
module. The
polarity (sink or
source) of a single
section module is
determined by the
manufacturer and
cannot be changed.
All I/O must be
capable of
operating from the
same power
source.

77. Split Module – 2 Sections
Group 0 Group 0
Group 1 Group 1
This module is split
into 2-sections. The
2-sections are the
same polarity,
(source), but each
section can be
powered from a
different power
source.

78. Split Module – 4 Sections
Group 0 Group 0
Group 3
Group 3
Group 1 Group 1
Group 2 Group 2
This module is split
into 4-sections. The
4-sections are the
same polarity,
(sink), but each
section can be
powered from a
different power
source.

79. Split Module – 2 Sections
This module is split
into 2-sections.
Each section can
be wired as either
sink or source and
use different power
sources. Also,
terminals CA and
CB can be jumped
and the entire
module can be
wired as either sink
or source.

80. Class Wiring Exercise
 Instructor led wiring exercise
 Use Training Panel Prints and discuss the
wiring of the panel.
 Equipment
 Training panel wiring schematics
 Digital Multimeter (DMM)