The document provides information about signal conditioning and electro-mechanical drives. It discusses topics such as signal conditioning including hardware, filtering noise, digital signal processing, and data acquisition systems. It also covers electro-mechanical drives including relays, solenoids, stepper motors, DC motors, servo motors, and pulse width modulation.

1. MODULE-2
Signal Conditioning and Electro Mechanical Drives
www.cambridge.edu.in
Department of
Mechanical Engineering
MECHATRONICS
18ME744
MANJUNATHA T V
Assistant Professor

2. Signal Conditioning and Electro Mechanical Drives:
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Department of Mechanical Engineering
Signal Conditioning: Introduction – Hardware – Digital I/O, Analog to digital
conversions, resolution,
Filtering Noise using passive components – Registers, capacitors, amplifying signals using
OP amps.
Digital Signal Processing – Digital to Analog conversion, Low pass, high pass, notch
filtering.
Data acquisition systems (DAQS), data loggers, Supervisory control and data acquisition
(SCADA), Communication methods.
Electro Mechanical Drives: Relays and Solenoids – Stepper Motors – DC brushed
motors – DC brushless motors – DC servo motors – 4-quadrant servo drives, PWM’s –
Pulse Width Modulation.

3. Signal Conditioning :
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Department of Mechanical Engineering
The output signal from the sensor of a measurement system has generally to be processed in
some way to make it suitable for the next stage of the operation. The signal may be, for
example,
too small and have to be amplified,
contain interference which has to be removed,
be non-linear and require linearisation,
be analogue and have to be made digital,
be digital and have to be made analogue,
 be a resistance change and have to be made into a currentchange,
be a voltage change and have to be made into a suitable size current change, etc.
All these changes can be referred to as signal conditioning . These changes to the output
from the sensors/ measurement system is termed as “Signal Conditioning”.
signal Conditioning is simply the process of refining the raw signal by use of solid state
electronic circuits such as amplifiers, attenuators, rectifiers, filters

4. Signal Conditioning :
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Department of Mechanical Engineering
Signal Conditioning process: Some of the processes that can occur in conditioning a signal are
outlined below
Protection: A microcontroller for example, requires a protection to prevent the damage as a result of high
current or voltage
Noise reduction/elimination : Filters are used to eliminate the noise exist in the signal of interest
Right type of signal :This can mean making the signal into a d.c. voltage or current. the resistance
change of a strain gauge has to be converted into a voltage change. This can be done by the use
of a Wheatstone bridge and using the out-of-balance voltage
level of the signal right: The signal from a thermocouple might be just a few millivolts. If the
signal is to be fed into an analogueto- digital converter for inputting to a microprocessor then it
needs to be made much larger, volts rather than millivolts. Operational amplifiers are widely
used for amplification.
Signal Manipulation: The signals from some sensors, e.g. a flowmeter, are non-linear and thus a
signal conditioner might be used so that the signal fed on to the next element
is linear.

5. Analogue-to-digital conversion :
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Department of Mechanical Engineering
the process required to change a sampled analog voltage into digital form. The process, called
analog-to-digital conversion, conceptually involves two steps: quantizing and coding.
Quantizing : is defined as the transformation of a continuous analog input into a set of
discrete output states.
Coding : is the assignment of a digital code word or number to each output shows the basic
elements of analogue-to-digital conversion.
In considering the specifications of ADCs the following terms will be encountered.
1 Conversion time, i.e. the time required to complete a conversion of the input signal. It
establishes the upper signal frequency that can be sampled without aliasing; the maximum
frequency is 1 / (2 conversion time).
2 Resolution, this being the full-scale signal divided by 2n, where n is the number of bits. It is
often just specified by a statement of the number of bits.
3 Linearity error, this being the deviation from a straight line drawn through zero and full-
scale. It is a maximum of ±2 LSB.

6. Analogue-to-digital conversion :
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Department of Mechanical Engineering
To properly acquire an analog voltage signal for digital processing, the following components must be properly selected and
applied in this sequence:
1. buffer amplifier
2. low-pass filter
3. sample and hold amplifier
4. analog-to-digital converter
The buffer amplifier isolates the output from the input (i.e., it draws negligible current and power from the input)
and provides a signal in a range close to but not exceeding the full input voltage range of the A/D converter.
The low-pass filter is necessary to remove any undesirable high- frequency components in the signal that could
produce aliasing. The cutoff frequency of the low-pass filter should be no greater than 1/2 the sampling rate.
The procedure used is that a clock supplies regular time signal pulses to the analogue-to-digital converter (ADC)
and every time it receives a pulse it samples the analogue signal. fig (b).
the clock signal which supplies the time signals at which the sampling occurs. fig (c).
The result of the sampling is a series of narrow pulses . fig (d).
A sample and hold unit is then used to hold each sampled value until the next pulse occurs which results shown in
fig (e). The sample and hold amplifier (see Section 5.12) maintains a fixed input value (from an instantaneous
sample) during the short conversion time of the A/D converter.
The sample and hold unit (maintians constant level) is necessary because the ADC requires a finite amount of
time, termed the conversion time, to convert the analogue signal into a digital one.

7. Analogue-to-digital conversion :
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Department of Mechanical Engineering

8. Resolution :
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Department of Mechanical Engineering
The converter should have a resolution and analog quantization size appropriate to the system and signal. The
word length possible determines the resolution of the element, i.e. the smallest change in input which will result
in a change in the digital output. The smallest change in digital output is 1 bit in the least significant bit position
in the word, i.e. the far right bit. Thus with a word length of n bits the full-scale analogue input VFS is divided
into pieces and so the minimum change in input that can be detected, i.e. the resolution, is VFS / . . Thus if we
have an ADC with a word length of 10 bits and the analogue signal input range is 10 V, then the number of
levels with a 10-bit word is = 1024 and thus the resolution is 10/1024 = 9.8 mV.
10
2
n
2
n
2

9. Analogue-to-digital converter :
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Department of Mechanical Engineering
A/D converters are designed based on a number of different principles: successive approximation, flash or parallel
encoding, single-slope and dual-slope integration, switched capacitor, and delta sigma.
The successive approximation A/D converter is very widely used because it is relatively fast and cheap.
When the start signal is applied, the sample and hold (S&H) amplifier latches the analog input. Then the control
unit begins an iterative process, where the digital value is approximated, converted to an analog value with the D/A
converter, and compared to the analog input with the comparator. When the D/A output equals the analog input, the
end signal is set by the control unit, and the correct digital output is available at the output.
If n is the resolution of the A/D converter, it takes n steps to complete the conversion. More specifically, the input
is compared to combinations of binary fractions (1/2, 1/4, 1/8, . . . , 1/2 n ) of the full-scale (FS) value of the A/D
converter.
The control unit first turns on the most significant bit (MSB) of the register, leaving all lesser bits at 0, and the
comparator tests the DAC output against the analog input. If the analog input exceeds the DAC output, the MSB is
left on (high); otherwise, it is reset to 0. This procedure is then applied to the next lesser significant bit and the
comparison is made again.
After n comparisons have occurred, the converter is down to the least significant bit (LSB). The output of the
DAC then represents the best digital approximation to the analog input. When the process terminates, the control
unit sets the end signal signifying the end of the conversion.

10. Analogue-to-digital conversion :
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Department of Mechanical Engineering

11. The ideal operational amplifier:
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The operational amplifier, or op amp, is a low-cost and versatile integrated circuit consisting of many internal transistors,
resistors, and capacitors manufactured into a single chip of silicon.
The operational amplifier is a high-gain d.c. amplifier, the gain typically being of the order of 100 000 or more, that is supplied
as an integrated circuit on a silicon chip. It has two inputs, known as the inverting input (-) and the non-inverting input (+).
Since the op amp is an active device, output voltages and currents can be larger than the signals applied to the inverting and
noninverting terminals.
An ideal model for an operational amplifier is as an amplifier with an
Infinite gain, infinite input impedance and zero output impedance, i.e. the
output voltage is independent of the load.
The symbol is sometimes used in the schematic to denote the infinite gain
and the assumption that it is an ideal op amp. The voltages are all referenced
to a common ground
Assumptions:
1. It has infinite impedance at both inputs; hence, no current is drawn from the
input circuits. Therefore,
2. It has infinite gain. As a consequence, the difference between the input voltages must be 0; otherwise, the output would be
infinite.
3. It has zero output impedance. Therefore, the output voltage does not depend on the output current

12. Inverting amplifier:
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input impedance : The input impedance of an amplifier is defined as the input voltage divided by the input
current,
output impedance : the output impedance being the output voltage divided by the output current.
Gain (A) : a measure of the "Amplification" of an amplifier, i.e. how much it increases the amplitude of a
signal. the ratio of the output signal amplitude to the input signal amplitude.
An inverting amplifier is constructed by connecting two external resistors to an op amp as shown in
Figure.. As the name implies, this circuit inverts and amplifies the input voltage,
The input is taken to the inverting input through a resistor R1 with the non-inverting input being connected to
ground. via the resistor R2 to the inverting input. Ie feedback (R2) from the output to the negative (inverting)
input. This so-called closed loop configuration results in stabilization of the amplifier and control of the gain.
When feedback is absent in an op amp circuit, the op amp is said to have an open loop configuration. This
configuration results in considerable instability due to the very high gain, and it is seldom used.
Applying Kirchhoff’s current law at node C and utilizing assumption 1, that no current
can flow into the inputs of the op amp, …………………………………………………..(1)
Also, because the two inputs are assumed to be shorted in the ideal model, C is effectively
at ground potential.

13. Inverting amplifier:
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Therefore, the voltage gain of the amplifier is determined simply by the external resistors RF and R, and it is always
negative. The reason this circuit is called an inverting amplifier is that it reverses the polarity of the input signal.
This results in a phase shift of 180 for periodic signals. The negative sign indicates that the output is inverted, i.e.
resulting in a larger amplitude signal 180° out of phase, with respect to the input

14. filters:
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What is a filter? A filter is a device that passes electric signals at certain frequencies or frequency ranges while
preventing the passage of others.Active Filters: Filter Circuit which consists of active components like
Transistors and Op-amps in addition to Resistors and Capacitors is called as Active Filter.
Passive Filters: Filter circuit which consists of passive components such as Resistors, Capacitors and Inductors
is called as Passive Filter.
filter can be further categorized based
on the operating frequency of a particular
circuit. They are:
Low Pass Filter
High Pass Filter
Band Pass Filter
Band Stop Filter
All Pass Filter
The term filtering is used to describe the process of removing a certain band of frequencies from a signal and
permitting others to be transmitted. The range of frequencies passed by a filter is known as the pass band, the
range not passed as the stop band and the boundary between stopping and passing as the cut-off frequency

15. www.cambridge.edu.in
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Low Pass Filter & high pass filter

16. Low Pass Filter circcits:
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Low Pass Filter

17. Pass bands for filters
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18. Notch Filter (Bandstop Filter)
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A notch filter (also known as a bandstop filter or reject filter) is defined as a device that rejects or blocks the transmission
of frequencies within a specific frequency range and allows frequencies outside that range. Notch filters eliminate
transmission of a narrow band of frequencies and allow transmission of all the frequencies above and below this band. As
it eliminates frequencies hence, it is also called a band elimination filter. As in the band-pass case, a band-reject filter can
be either wideband or narrow-band.
A notch filter is essentially a band stop filter with a narrow stop band and two pass bands.
If the filter is wideband, it is referred to as a band-reject filter and if the filter is narrow-band, it is referred to as a notch
filter.
Thus, the function of a Notch Filter is to passing all those frequencies from zero (DC) up to lower cut-off frequency(fL)
and above higher cut-off frequency(fH), and reject all those frequencies that lie in the bandwidth region i.e., BW= fH-fL.
if a Notch Filter has a stopband frequency from 100 MHz to 200 MHz, then it will pass all the signals from DC to
frequency of 100 MHz and above 200 MHz, it will only reject frequency between 100 MHz to 200 MHz.
The upper portion of the notch filter circuit is a passive RC low pass filter. This portion comprises two resistors R1,
R2,and capacitor C1 . This filter will allow the signals having frequencies lower than the higher cut-off frequency (fH).
The lower portion of the notch filter circuit is a passive RC high-pass filter. This portion comprises two capacitors C2,
C3,and resistor R3, This filter will allow the signals having frequencies higher than the lower cut-off frequency (fL)

19. Notch Filter (Bandstop Filter)
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Department of Mechanical Engineering

20. Notch Filter Applications
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A Notch filter is generally used in communication systems, Instrumentation and control systems, and the
biomedical field to eliminate 50/60 Hz power line interference.
Notch filter or Bandstop filter is widely used in electronics and communications circuits to reject a band of
unwanted frequencies and allowing transmission of other frequencies with minimum loss.
Switching type of AC & DC motor drives, converters, and inverters cause sinusoidal disturbances at
certain harmonics of the line frequency. The use of a notch filter eliminates such unwanted disturbances and
enables accurate measurements.
 It is highly preferred in image and signal processing to reject unwanted frequencies i.e. noise.
It is used in audio signal processing, for removing a specific range of unwanted frequencies i.e. noise or hum.
It is used in telephone technology, DSL, and other internet services as a line noise reducer to reduce
unwanted interference.
It is used in guitar amplifiers, instrument amplifiers, acoustic guitar, mandolin, bass instrument amplifier, and
PA systems to reduce a specific humming sound that may produce after instruments are plugged. .
It is used in medical field applications i.e. in ECG (Electrocardiogram) measurements, to eliminate dc
component.

21. Resistor
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A resistor is a dissipative element that converts electrical energy into heat. The unit of resistance is the ohm (Ω).
Resistance is a material property whose value is the slope of the resistor’s voltage-current curve For an ideal
resistor, the voltage-current relationship is linear, and the resistance is constant. However, real resistors are
typically nonlinear due to temperature effects.
 As the current increases, temperature increases resulting in higher resistance. Also a real resistor has a limited
power dissipation capability designated in watts, and it may fail when this limit is exceeded. If a resistor’s material
is homogeneous and has a constant cross-sectional
area, such as the cylindrical wire, then the resistance is given by

22. Resistor
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Department of Mechanical Engineering
Actual resistors used in assembling circuits are packaged in various forms including axial-lead components, surface
mount components, and the dual inline package (DIP) and the single in-line package (SIP), which contain multiple
resistors in a package that conveniently fits into circuit boards
An axial-lead resistor’s: An axial-lead resistor’s value and tolerance are usually coded with four colored bands ( a, b,
c, tol ) as illustrated in Figure. A resistor’s value and tolerance are expressed as
where the a represents the tens digit, the b
band represents the ones digit, the c
band represents the power of 10, and the tol
band represents the tolerance or uncertainty
as a percentage of the coded resistance value.

23. Capacitor
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Department of Mechanical Engineering
A capacitor is a two-terminal electrical device that possesses the ability to store energy in the form of an electric charge. It
consists of two electrical conductors that are separated by a distance. The space between the conductors may be filled by
vacuum or with an insulating material known as a dielectric. The ability of the capacitor to store charges is known as
capacitance. Capacitor is a passive element that stores energy in the form of an electric field. This field is the result of a
separation of electric charge. The simplest capacitor consists of a pair of parallel conducting plates separated by a dielectric
material.
the parallel plate capacitor: It consists of two parallel plates separated by a dielectric. When we connect a DC voltage
source across the capacitor, one plate is connected to the positive end (plate I) and the other plate to the negative end (plate II).
When the potential of the battery is applied across the capacitor, plate I become positive with respect to plate II. At the steady-
state condition, the current tries to flow through the capacitor from its positive plate to its negative plate. But it is unable to
flow due to the separation of these with an insulating material.

24. Capacitor
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An electric field appears across the capacitor. The positive plate (plate I) accumulates positive charges from the battery, and
the negative plate (plate II) will accumulate negative charges from the battery. After a point, the capacitor holds the
maximum amount of charge as per its capacitance with respect to this voltage. This time span is called the charging time of
the capacitor.

25. RC Filters
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Department of Mechanical Engineering
.Very simple analog low pass or high pass filters can be constructed from resistor and capacitor (RC) networks.
In the low pass case, a potential divider is formed from a series resistor followed by a shunt capacitor, as
illustrated in Figure. The filter input is at one end of the resistor and the output is at the point where the
resistor and capacitor join. The RC filter works because the capacitor reactance reduces as the frequency
increases. It should be remembered that the reactance is 90 degree out of phase with resistance. For frequency
changes the resistor remains constant.
At low frequencies the reactance of the capacitor is very high and the output voltage is almost equal to the
input, with virtually no phase difference. At the cutoff frequency, the resistance and the capacitive reactance
are equal and the filter's output is of the input voltage, or -3 dB. At this frequency the output will not be
in phase with the input: it will lag by 45 degree due to the influence of the capacitive reactance. At frequencies
above the 3 dB attenuation point, the output voltage will reduce further. The rate of attenuation will be 6 dB
per doubling of frequency (per octave). As the frequency rises, the capacitive reactance falls and the phase shift
lag approaches 90 degree.
Although this is a description of a low pass filter, a high pass response can be obtained by swapping the
components. Placing a capacitor in series with the input, followed by a shunt resistor, gives a filter with the
same 3dB frequency, but with a 45 degree phase lead. However. as the frequency rises, the attenuation and
phase shift decrease.

26. RC Filters
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.

27. Digital Signal Processing
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.The term digital signal processing or discrete-time signal processing is used for the processing applied to a
signal by a microprocessor. Digital signals are discrete-time signals in that they are not continuous functions of
time but exist at only discrete times. Where as signal conditioning of analogue signals requires components
such as amplifiers and filter circuits, digital signal conditioning can be carried out by a program applied to a
microprocessor, i.e. processing the signal.
To change the characteristics of a filter used with analogue signals it is necessary to change hardware
components, whereas to change the characteristics of a digital filter all that is necessary is to change the
software, i.e. the program of instructions given to a microprocessor
With a digital signal processing system there is an input of a word representing the size of a pulse and an
output of another word. The output pulse at a particular instant is computed by the system as a result of
processing the present input pulse, together with previous pulse inputs and possibly previous system outputs.

28. Digital-to analogue converter:
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.The input to a digital-to-analogue converter (DAC) is a binary word; the output is an analogue signal that
represents the weighted sum of the nonzero bits represented by the word.
A simple form of DAC uses a summing amplifier to form the weighted sum of all the non-zero bits in the input
word.
The reference voltage is connected to the resistors by means of electronic switches which respond to binary 1.
The values of the input resistances depend on which bit in the word a switch is responding to, the value of the
resistor for successive bits from the LSB being halved (divided) Hence the sum of the voltages is a weighted sum
of the digits in the word. Such a system is referred to as a weighted-resistor network.
The function of the op-amp circuit is to act as a buffer to ensure that the current out of the resistor network is
not affected by the output load and also so that the gain can be adjusted to give an output range of voltages
appropriate to a particular application.
this form of DAC tends be limited to 4-bit conversions

29. Digital-to analogue converter
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.

30. Data acquisition systems
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The term data acquisition, or DAQ, is used for the process of taking data from sensors and inputting that data
into a computer for processing. The sensors are connected, generally via some signal conditioning, to a data
acquisition board which is plugged into the back of a computer.
Data acquisition generally relates to the process of collecting the input data in digital form as rapidly,
accurately, and economically as necessary. The basic instrumentation used may be a DPM with digital outputs, a
shaft digitizer, or a sophisticated high speed resolution device.
A typical Data Acquisition System and DAQ board is a printed circuit board that, for analogue inputs, basically
provides a multiplexer, amplification, analogue-to-digital conversion, registers and control circuitry so that
sampled digital signals are applied to the computer system (storage and display systems).
when the acquisition is complete and then the computer can interrupt any program it is implementing, read
the data from the DAQ and then continue with its program.
Processing may consist of a large variety of operations, ranging from simple comparison to complicated
mathematical manipulations. It can be for such purposes as collecting information (averages, statistics),
converting the data into a useful form , using data for controlling a process, performing repeated calculations to
separate signals buried in the noise, generating information for display, and various other purposes

31. Data acquisition systems
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The important Factors to Consider When Setting up a Data Acquisition System are as follows.
1. Accuracy and resolution 2. Number of channels to be monitored 3. Analog or digital signal
4. Single channel or multichannel 5. Sampling rate per channel 6. Signal conditioning requirements of each channel
7. Cost

32. Data loggers
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A data logger or a data recorder is an electronic device or a computer program that continuously records data
over time in relation to the location either using a built-in instrument or through an externally interfaced one.
typically over a long period of time for many applications.
Once the program has been set by a computer, it can be put onto a memory card which can be inserted into the
logger or have the program downloaded to it from a computer, so enabling it to carry out the required DAQ
functions.
shows the basic elements of a data logger. Such a unit can monitor the inputs from a large number of sensors.
Inputs from individual sensors, after suitable signal conditioning, are fed into the multiplexer. The multiplexer is
used to select one signal which is then fed, after amplification, to the ADC. The digital signal is then processed by
a microprocessor. The microprocessor is able to carry out simple arithmetic operations, perhaps taking the
average of a number of measurements. The output from the system might be displayed on a digital meter that
indicates the output and channel number, used to give a permanent record with a printer, stored on a floppy disk
or transferred to perhaps a computer for analysis.

33. Data loggers
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Department of Mechanical Engineering

34. SCADA
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Department of Mechanical Engineering
SCADA is an acronym for Supervisory Control and Data Acquisition. SCADA systems are used to monitor and
control a plant or equipment in industries such as telecommunications, water and waste control, energy, oil
and gas refining and transportation.
These systems encompass the transfer of data between a SCADA central host computer and a number of
Remote Terminal Units (RTUs) and/or Programmable Logic Controllers (PLCs), and the central host and the
operator terminals.
SCADA system gathers information transfers the information back to a central site, then alerts the home
station that a problem has occurred, carrying out necessary analysis and control, such as determining if the
problem is critical, and displaying the information in a logical and organized fashion. (Ex: leak in pipe lines).
These systems can be relatively simple, such as one that monitors environmental conditions of a small office
building, or very complex, such as a system that monitors all the activity in a nuclear power plant or the activity
of a municipal water system.
Today many systems are monitored using the infrastructure of the corporate Local Area Network (LAN)/Wide
Area Network (WAN). Wireless technologies are now being widely deployed for purposes of monitoring.

35. SCADA
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Field Data Interface Devices: Field data interface devices form the "eyes and ears" of a SCADA system, the
information that is passed to and from the field data interface devices must be converted to a form that is
compatible with the language of the SCADA system. To achieve this, some form of electronic field data
interface is required. RTUs, also known as Remote Telemetry Units, provide this interface. They are primarily
used to convert electronic signals received from field interface devices into the language (known as the
communication protocol) used to transmit the data over a communication channel.
Communications Network: The communications network is intended to provide the means by which data
can be transferred between the central host computer servers and the field-based RTUs. The Communication
Network refers to the equipment needed to transfer data to and from different sites. The medium used can
either be cable, telephone or radio.
Central Host Computer: The central host computer or master station is most often a single computer or a
network of computer servers that provide a man-machine operator interface to the SCADA system. The
computers process the information received from and sent to the RTU sites and present it to human operators
in a form that the operators can work with. Operator terminals are connected to the central host computer by
a LAN/WAN so that the viewing screens and associated data can be displayed for the operators.
Operator Workstations and Software Components: the operator terminals are clients that request and send
information to the central host computer based on the request and action of the operators.

36. SCADA
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An important aspect of every SCADA system is the computer software used within the system. The most
obvious software component is the operator interface or Man Machine Interface/Human Machine Interface
(MMI/HMI) package. The proprietary software often is configured for a specific hardware platform and may not
interface with the software or hardware produced by competing vendors.

37. SCADA
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Objectives of SCADA
Monitor: SCADA systems continuously monitor the physical parameters
Measure: It measures the parameter for processing
Data Acquisition: It acquires data from RTUs (Remote Terminal Units), data loggers, etc
Data Communication: It helps to communicate and transmit a large amount of data between MTU and RTU
units
Controlling: Online real-time monitoring and controlling of the process
Automation: It helps for automatic transmission and functionality Various other communication mediums like
fiber optic cables, twisted pair cables, etc. are also used.

38. SCADA
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39. SCADA
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Department of Mechanical Engineering
SCADA is widely used in different areas from chemical, gas, water, communications and power systems. The list of
applications of SCADA can be listed as follows.
1. Electric power generation, transmission and distribution: Electric utilities use SCADA systems to detect current flow and
line voltage, to monitor the operation of circuit breakers, and to take sections of the power grid online or offline.
2. Water, Waste Water Utilities and Sewage: State and municipal water utilities use SCADA to monitor and regulate water
flow, reservoir levels, pipe pressure and other factors.
3. Buildings, facilities and environments: Facility managers use SCADA to control HVAC, refrigeration units, lighting and
entry systems.
4. Oil and Gas Trans & Distributions:
5. Wind Power Generation
6. Communication Networks:
7. Industrial Plans and Process Control:
8. Manufacturing: SCADA systems manage parts inventories for just-in-time manufacturing, regulate industrial automation
and robots, and monitor process and quality control.
9. Mass transit and Railway Traction: Transit authorities use SCADA to regulate electricity to subways, trams and trolley
buses; to automate traffic signals for rail systems; to track and locate trains and buses; and to control railroad crossing gates.
10. Traffic signals: SCADA regulates traffic lights, controls traffic flow and detects out-of-order signals.

40. SCADA
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Benefits of SCADA:
The important benefits of an EMS can be addresses as the following functions:
1. Continuous monitoring of process.
2. Real time control.
3. Automation and Protection.
4. Remote control and operation.
Functions of SCADA:
The important functions of an SCADA are listed below
1. Data Acquisition
2. Information Display
3. Supervisory Control
4. Alarm Processing
5. Information Storage and Reports
6. Sequence of Event Acquisition
7. Data Calculation
8. Special RTU Processing/Control

41. Communications methods:
www.cambridge.edu.in
Department of Mechanical Engineering
Ethernet - A system for connecting a number of computer systems to form a local area network, with protocols
to control the passing of information.
Telephone Line - A system that utilizes electrical signals in order to transmit data over a distance using a single
pair of copper (traditionally) wires.
Radio/Wireless - A system that uses radio transmitters and receivers to send data over short distances.
Typically requires line of sight for best application.
Cellular - Based on the cellular phone technology to transmit data, regardless of distance, but dependent on
cellular signal coverage.
Satellite - Similar to the cellular phone platform, but utilizing satellites instead of ground-based cellular towers.
Wi-Fi - A technology increasing in popularity that allows an electronic device to exchange data wirelessly (using
radio waves) over a computer network, including high-speed internet connections. WPA2 is present in almost
all currently available equipment, and its use should be mandated for supports robust security.
Microwave – A system for providing long-range connectivity between two sites, utilizing either inexpensive
public frequencies or FCC-licensed spectrum

42. Communications methods:
www.cambridge.edu.in
Department of Mechanical Engineering
Optical Fiber Line- Similar to the traditional copper telephone lines, but differs by utilizing optical fibers made of
glass or plastic and uses light to transmit the data, with is faster and has less losses as compared to copper wires.
Optical fibers consist of an inner core and cladding of silica glass and a plastic jacket that physically protects the
fiber. Two types of fibers are usually considered: multi-mode graded index and single-mode step index fiber.
Single-mode fiber supports higher signaling speeds than the multi-mode fiber due to its smaller diameter and mode
of light propagation. Communication services usually supported by optical fiber include voice, data (low speed),
SCADA, protective relaying, telemetering, video conferencing, high speed data, and telephone switched tie trunks.

43. Solenoids
www.cambridge.edu.in
Department of Mechanical Engineering
a solenoid consists of a coil and a movable iron core called the armature. When the coil is energized with current, the core
moves to increase the flux linkage by closing the air gap between the cores. The movable core is usually spring-loaded to
allow the core to retract when the current is switched off.
The force generated is approximately proportional to the square of the current and inversely proportional to the square of
the width of the air gap.
The force generated is mainly depends up on the number of coils and
the amount of current flowing in the circuit.
The frame is essentially permeable magnetic laminations excited by the
coil. The plunger is actuated by a magnetic field pulling it to the down position
against spring pressure.
Solenoids are inexpensive, and their use is limited primarily to on-off
applications such as latching, locking, and triggering. They are frequently used in
home appliances (e.g., washing machine valves), automobiles
(e.g., door latches and the starter solenoid),
pinball machines (e.g., plungers and bumpers), and factory automation

44. Relay
www.cambridge.edu.in
Department of Mechanical Engineering
Definition: The relay is the device that open or closes the contacts to cause the operation of the other electric control. It
detects the intolerable or undesirable condition with an assigned area and gives the commands to the circuit breaker to
disconnect the affected area. Thus protects the system from damage.
It works on the principle of an electromagnetic attraction. When the circuit of the relay senses the fault current, it energises
the electromagnetic field which produces the temporary magnetic field.
Relay have two sets of electrically conductive contacts. Relays may be “Normally Open”, or “Normally Closed”.
In the normally open position, the contacts are closed only when the field current is “ON” and the switch contacts are pulled
towards the inductive coil.
In the normally closed position, the contacts are permanently closed when the field current is “OFF” as the switch contacts
return to their normal position.
Frame: Heavy-duty frame that contains and supports the parts of the relay.
Coil: Wire is wound around a metal core. The coil of wire causes an electromagnetic field.
Armature: A relays moving part. The armature opens and closes the contacts. An attached spring returns the armature to its
original position.
Contacts: The conducting part of the switch that makes (closes) or breaks (opens) a circuit.

45. Relay
www.cambridge.edu.in
Department of Mechanical Engineering

46. classification of electrical motors
www.cambridge.edu.in
Department of Mechanical Engineering

47. classification of electrical motors
www.cambridge.edu.in
Department of Mechanical Engineering

48. Direct current (DC) motors
www.cambridge.edu.in
Department of Mechanical Engineering
Direct current (DC) motors are used in a large number of mechatronic designs because of the torque-speed
characteristics achievable with different electrical configurations. DC motor speeds can be smoothly controlled
and in most cases are reversible. Since DC motors have a high ratio of torque to rotor inertia, they can respond
quickly. Also, dynamic braking, where motor-generated energy is fed to a resistor dissipater, and regenerative
braking, where motor-generated energy is fed back to the DC power supply, can be implemented in applications
where quick stops and high efficiency are desired.
Direct current (DC) motors works on the principle of Flemings left hand rule when current carrying
conductor placed in a magnetic field it expiries the torque and tendency to move this is known as motoring
action. If direction in the current is reversed the direction of rotation also reverses. When magnetic field and
electric field interact it produce mechanical force which tends to rotate the armature.
Dc motor contains mainly following parts,
The stator contains either permanent magnets or electromagnets and remains stationary.
The rotor, also referred to as the armature, is the part of the motor that rotates.
The commutator is the part of the motor that makes a connection between the rotor and the brushes.
The brushes are connected to the DC power source

49. Direct current (DC) motors
www.cambridge.edu.in
Department of Mechanical Engineering

50. Brushed DC motor
www.cambridge.edu.in
Department of Mechanical Engineering
It typically consists of a pair of permanent magnets named as the stator and a motor coil named as the rotor
connected to a commutator. In this motor, armature winding is on rotor and permanent magnets are always on the
stator.
In this type of motors, magnetic field is produced by passing current through a commutator and brush which are
inside the rotor. Hence, they are called Brushed Motors. The brushes are made up of carbon. These can be
separately excited or self-excited motors.
The stator part of the motor consists of coils connected in a circular fashion in such a way that the required
alternative north and south poles are formed. This coil setup can be in series or in parallel to the rotor coil
winding forming series wound DC motors and shunt wound DC motors.
The armature or the rotor part of the DC motor consists of
Commutator which essentially a current carrying conductor
connected at one end to copper segments which are electrically
isolated. To make the motor rotate in a constant direction, "direct current"
commutators make the current reverse in direction every half a cycle
(in a two-pole motor) thus causing the motor to continue to rotate in
the same direction. External power can be connected to commutator or
via the brushes as the armature rotates.

51. Brushed DC motor
www.cambridge.edu.in
Department of Mechanical Engineering

52. Brushed DC motor
www.cambridge.edu.in
Department of Mechanical Engineering
Permanent Magnet DC Motors: The permanent magnet dc motor can be defined as a motor which includes a
permanent magnet pole is called Permanent Magnet DC Motor. In this motor, the magnet can be used to make the
flux working within the air gap in its place of the field winding. The rotor structure is similar to the straight DC
Motor. PMDC Motor’s rotor includes armature core, commutator, & armature winding. Normally, in a conventional
DC motor, there are two kinds of winding such as armature as well as Filed. he main function of field winding is to
produce the functioning magnetic flux within the air gap as well as wound on the stator of the motor while
armature winding can be wound on the rotor. Inactive carbon brushes are pushed on the commutator like in
conventional DC motor. The operating voltage of the PMDC motor is 6 volts, 12 volts otherwise 24 volts DC supply
attained from the voltage sources.
The speed/torque characteristics of a permanent magnet DC motor
are more linear than stator wound DC motors.
The size of these motors is smaller
These motors are cheaper
The disadvantage of a brushed DC motor is the occurrence of
sparks between commutator and brushes under heavy load
conditions.
This generates large amount of heat and reduces the lifetime
of the motor.

53. Brushed DC motor
www.cambridge.edu.in
Department of Mechanical Engineering
.
PMDC motors are mainly used in automobiles to
operate windshield wipers and washers, to raise
the lower windows, to drive blowers for heaters
and air conditioners etc. They are also used in
computer drives. used in toy industries., electric
toothbrushes, portable vacuum cleaners, food
mixers.

54. Series Motors:
www.cambridge.edu.in
Department of Mechanical Engineering
Series Motors: In case of series DC motors, the field winding and armature windings are connected in series with the
power supply. Hence same current flows in the field winding and armature winding.
A series wound motor is also called Universal motor as it works with either an AC voltage supply or a DC voltage supply.
A series wound motor will always rotate in the same direction regardless of the polarity of the voltage source. This is
because if we change the polarities, the polarity of the armature winding and the direction of the magnetic field are
reversed simultaneously. A characteristic of series motors is the motor develops a large amount of starting torque.
However, speed varies widely between no load and full load. Series motors cannot be used where a constant speed is
required under varying loads.

55. Shunt DC Motors:
www.cambridge.edu.in
Department of Mechanical Engineering
Shunt DC Motors: In case of shunt DC motors, the field winding and armature winding are connected in parallel across
the same supply and hence the field windings are exposed to entire terminal same voltage. Even though the supply is
same, the field current and armature current are different. The speed of a shunt DC motor is constant and doesn’t vary
with mechanical load at the output.
Shunt would motor able to runs at a predetermined speed.
The speed of a dc shunt motor is sufficiently constant.
Direct current machines can use for heavy industrial applications where the
torque and speed wider range.

56. Brushless DC motor
www.cambridge.edu.in
Department of Mechanical Engineering
Brushless DC Motor
Brushless DC motors typically consist of a permanent magnet rotor and a coil wound stator. This design by using
permanent magnets in rotor eliminates the need for brushes in the rotor part. Hence, in contrast to brushed DC motors,
these type do not contain any brushes and therefore no wear and tear of brushes as little amount of heat is generated.
As there are no brushes in the motor, there should be some other means to detect the angular position of the rotor. Hall
Effect sensors are used to produce the feedback signals that are required to control any semiconductor switching devices.
while the magnetic field generated by the stationary magnets remains
fixed. To change the rotation speed, it must should change the voltage
for the coils. With a BLDC motor the permanent magnet rotation is
achieved by changing the direction of the magnetic fields generated by
the surrounding stationary coils. To control the rotation, there should
adjust the magnitude and direction of the current into these coils.
Brushless DC motors are more expensive than brushed DC motors and
are more efficient than their brushed cousins
The advantages of a brushless motor over brushed motors are high
power-to-weight ratio, high speed, nearly instantaneous control of
speed (rpm) and torque, high efficiency, and low maintenance.

57. Brushless DC motor
www.cambridge.edu.in
Department of Mechanical Engineering

58. Stepper Motors
www.cambridge.edu.in
Department of Mechanical Engineering
A special type of DC motor, known as a stepper motor, A stepper motor is an electromechanical device which
converts electrical pulses into discrete mechanical movements . A stepper motor is brushless dc motor whose rotor
rotates in discrete angular displacements when its stator windings are energized in a programmed manner. Rotation
occurs because of magnetic interaction between rotor poles and poles of the sequentially energized winding. The
rotor has no electrical windings, but has salient and magnetic/or magnetized poles.
It moves in accurate angular increments, known as steps, in response to digital pulses sent to an electric drive
circuit. They are powered by DC sources and require digital circuitry to produce coil energizing sequences for
rotation of the motor.
The number and rate of the pulses control the position and speed of the motor shaft.
The stator has eight poles, and the rotor has six poles. The rotor will require 24 pulses of electricity to move the
24 steps to make one complete revolution. Another way to say this is that the rotor will move precisely 15° for each
pulse of electricity that the motor receives.
Generally, stepper motors are manufactured with steps per revolution of 12, 24, 72, 144, 180, and 200,
resulting in shaft increments of 30⁰ , 15⁰, 5⁰, 2.5⁰ , 2⁰, and 1.8⁰ step.
One of the most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop
system. Open loop control means no feedback information about position is needed. This type of control eliminates
the need for expensive sensing and feedback devices such as optical encoders. The rotor position is known simply
by keeping track of the input step pulses.

59. Stepper Motors
www.cambridge.edu.in
Department of Mechanical Engineering
Construction & Working Principle
The construction of a stepper motor is fairly related to a DC motor. It includes a permanent magnet like Rotor
which is in the middle & it will turn once force acts on it. This rotor is enclosed through a no. of the stator which is
wound through a magnetic coil all over it. The stator is arranged near to rotor so that magnetic fields within the
stators can control the movement of the rotor.
The stepper motor can be controlled by energizing every stator one by one. So the stator will magnetize & works
like an electromagnetic pole which uses repulsive energy on the rotor to move forward. The stator’s alternative
magnetizing as well as demagnetizing will shift the rotor gradually & allows it to turn through great control.
stepper motor working principle: In step 0, the rotor is in equilibrium, because opposite poles on the stator and
rotor are adjacent to and attract each other. Unless the magnet polarities of the stator poles are changed, the rotor
remains in this position and can withstand an opposing torque up to a value called the holding torque. When the
stator polarities are changed as shown (step 0 to step 1), a torque is applied to the rotor, causing it to move 90⁰ in
the clockwise direction to a new equilibrium position shown as step 1. When the stator polarities are again changed
as shown (step 1 to step 2), the rotor experiences a torque driving it to step 2. By successively changing the stator
polarities in this manner, the rotor can move to successive equilibrium positions in the clockwise direction.
Counterclockwise motion can be achieved by applying the polarity sequence in the opposite direction

60. Stepper Motors
www.cambridge.edu.in
Department of Mechanical Engineering

61. Stepper Motors
www.cambridge.edu.in
Department of Mechanical Engineering
Variable Reluctance Motor
Figure shows the construction of Variable Reluctance motor. The cylindrical rotor is made of soft steel and has four poles as
shown in Fig. It has four rotor teeth, 90⁰ apart and six stator poles, 60⁰ apart. Electromagnetic field is produced by activating
the stator coils in sequence. It attracts the metal rotor. When the windings are energized in a reoccurring sequence of 2, 3, 1,
and so on, the motor will rotate in a 30⁰ step angle. In the non-energized condition, there is no magnetic flux in the air gap, as
the stator is an electromagnet and the rotor is a piece of soft iron, The permanent magnet stepper motor has the advantage of a
small residual holding torque, called the detent torque, ie motor produces amount of torque even when the stator is not
energized. This type of stepper motor is called a variable reluctance stepper.
two important features of variable reluctance motor
the reluctance is not constant: One more way of obtaining the variable
reluctance is by modifying the air gap between the stator rotor windings.
The rotor rotates not in continuous motion but in steps
Step Angle = (360/m*Nr)
Where m is the number of stator phases and Nr is the number of rotor poles.

62. Stepper Motors
www.cambridge.edu.in
Department of Mechanical Engineering
Permanent magnet (PM) stepper motor
In this type of motor, the rotor is a permanent magnet. Unlike the other stepping motors, the PM motor rotor has no teeth and
is designed to be magnetized at a right angle to its axis. Figure. shows a simple, 90⁰ PM motor with four phases (A-D).
Applying current to each phase in sequence will cause the rotor to rotate by adjusting to the changing magnetic fields.
Although it operates at fairly low speed, the PM motor has a relatively high torque characteristic. These are low cost motors
with typical step angle ranging between 7.5⁰ to 15⁰.

63. servomotor
www.cambridge.edu.in
Department of Mechanical Engineering
When a motor is used in a position or speed control application with sensor feedback to a controller, it is referred to
as a servomotor
Servomotors are special electromechanical devices that produce precise degrees of rotation. A servo motor is a DC
or AC or brushless DC motor combined with a position sensing device. Servomotors are also called control motors as
they are involved in controlling a mechanical system.
A reference input is sent to the servo amplifier, which controls the speed of the servomotor.
A feedback device is mounted on the machine, which is either an encoder or resolver. This device changes
mechanical motion into electrical signals and is used as a feedback.
This feedback is sent to the error detector, which compares the actual operation with that of the reference input. If
there is an error, that error is fed directly to the amplifier, which will be used to make necessary corrections in control
action.

64. D C servomotor
www.cambridge.edu.in
Department of Mechanical Engineering
A small DC motor will rotate at high speed, but its torque is insufficient to move any load. A DC servo motor
consists of four parts: a normal DC motor, a gearbox for speed control, a control circuit and a position sensing
unit. The gearbox will take the high speed input and converts into a slower but more practical speed. while at the
same time increasing the torque.
 The position sensing unit is generally a potentiometer. The control circuit is an error detector amplifier. In DC
servo motors, the position of the shaft is feedback to a control circuit and therefore, they are used in closed loop
applications.
The potentiometer is connected to the shaft. It allows the control circuit to monitor the position of the motor.
This position is compared with a reference input signal by the control circuit. The output of the control circuit is
feedback to the motor. If there is any mismatch in the current position and the reference position, an error signal is
generated at the output of the error detecting amplifier. Based on this signal, the shaft rotates and goes to the
required location and stops.

65. D C servomotor
www.cambridge.edu.in
Department of Mechanical Engineering

66. 4-quadrant servo drives,
www.cambridge.edu.in
Department of Mechanical Engineering
A servo system capable of controlling velocity and torque in both positive and negative directions is known as
having "four-quadrant" operation.
Four Quadrant Operation of any drives or DC Motor means that the machine operates in four quadrants.
They are Forward Braking, Forward motoring, Reverse motoring and Reverse braking.
In motoring mode, the machine works as a motor and converts the electrical energy into mechanical energy,
supporting its motion. In braking mode, the machine works as a generator and converts mechanical energy into
electrical energy and as a result, it opposes the motion.
Operation in quadrants 1 and 3 is defined as "Motoring," meaning that speed and torque are in the same
direction (both positive or both negative). This typically occurs when a system is driving a load and power is
being consumed by the motor supplying mechanical energy.
Quadrants 2 and 4 are defined as "Generating" (sometimes called Regenerating), meaning that speed and
torque are in opposite directions (one negative and one positive). Generation occurs when the torque of the motor
is opposing the direction of rotation and the motor is generating electrical energy. This energy can either be given
back to the mains voltage (regenerate energy) or transferred to heat in a brake resistor or stored in capacitors

67. 4-quadrant servo drives
www.cambridge.edu.in
Department of Mechanical Engineering

68. Modulation
www.cambridge.edu.in
Department of Mechanical Engineering
Pulse modulation types
Analog Pulse Modulation
 Pulse Amplitude Modulation
(PAM)
Pulse width Modulation (PWM)
 Pulse Position Modulation (PPM)

69. Pulse Width Modulation
www.cambridge.edu.in
Department of Mechanical Engineering
Pulse Width Modulation(PWM) : is a digital technology that uses the amount of power delivered to a device
that can be changed. It is a type of analog modulation. In pulse width modulation or pulse duration modulation,
the width of the pulse carrier is varied in accordance with the sample values of message signal or modulating
signal or modulating voltage. In pulse width modulation, the amplitude is made constant and width of pulse and
position of pulse is made proportional to the amplitude of the signal.
PWM can vary the pulse width in three ways
1. By keeping the leading edge constant and vary the pulse width with respect to leading edge
2. By keeping the tailing constant.
3. By keeping the center of the pulse constant.
Duty Cycle in PWM: The duty cycle of the PWM signal refers to the ratio of the time that the signal is in a
high(on) state over the total time it takes to complete one cycle. It is commonly expressed as a percentage or a
ratio. The duty cycle and frequency of a PWM signal determine its behavior of signal.
Pulse-width modulation (PWM), as it applies to motor control, is a way of delivering energy through a
succession of pulses rather than a continuously varying (analog) signal. By increasing or decreasing pulse width,
the controller regulates energy flow to the motor shaft. The motor’s own inductance acts like a filter, storing
energy during the “on” cycle while releasing it at a rate corresponding to the input or reference signal.
EX: In practical, we use 555 Timer which is the best way for generating the pulse width modulation signals. By
configuring the 555 .

70. Pulse Width Modulation
www.cambridge.edu.in
Department of Mechanical Engineering

71. Pulse Width Modulation
www.cambridge.edu.in
Department of Mechanical Engineering

72. Pulse Width Modulation
www.cambridge.edu.in
Department of Mechanical Engineering
Advantages of Pulse Width Modulation (PWM):
As like pulse position modulation, noise interference is less due to amplitude has been made constant.
Signal can be separated very easily at demodulation and noise can also be separated easily.
Synchronization between transmitter and receiver is not required unlike pulse position modulation.
Disadvantages of Pulse Width Modulation (PWM):
 Power will be variable because of varying in width of pulse. Transmitter can handle the power even for
maximum width of the pulse.
Bandwidth should be large to use in communication, should be huge even when compared to the pulse
amplitude modulation.
Applications of Pulse Width Modulation (PWM):
PWM is used in telecommunication systems.
PWM can be used to control the amount of power delivered to a load without incurring the losses. So, this
can be used in power delivering systems.
 Audio effects and amplifications purposes also used.
PWM signals are used to control the speed of the robot by controlling the motors.
PWM is also used in robotics.
 Embedded applications.
 Analog and digital applications etc.