Automatic Speed Control System in Automobiles

7/22/2019 Automatic Speed Control System in Automobiles

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CHAPTER 1

INTRODUCTION

We use intelligent instruments in every part of our lives. It won’t take

much time that we realize that most of our tasks are being done by electronics.

Very soon, as we shall see, they will perform one of the most complicated

tasks that a person does in a day, that of driving a vehicle. This is for the better.

As the days of manned driving are getting extremely numbered, so are those of

traffic jams, bad, dangerous and rough drivers and more importantly,

accidents. Automation of the driving control of – four wheelers is one of the

most vital need of the hour. This technology can very well implement what

was absent before, controlled lane driving. These systems have been

implemented in France, Japan & U.S.A. by many companies, but only for cars

and mass transport networks. In those systems, the acceleration and brake

controls are left to the driver while the micro-processor simply handles the

steering and the collision detection mechanism. The driver just has to sit back

and enjoy the ride. Here we are designing a system that will slow down the four wheeler

after measuring the distance from the nearby obstacle, if the distance is less

than a certain limit. So to avoid rash driving and to prevent loosing of valuable

property we need some safety systems in the vehicles. We can make this true

by using sensors and other electronic components. But those have more cost

which causes increase in cost of the vehicle. Without using those electronic

components also we can achieve this by using mechanical arrangements. To

achieve we designed a simple mechanical system for providing safety, for

avoiding rash driving in highly populated regions.



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CHAPTER 2

LITERATURE SURVEY

This chapter reviews some of the work related to the study of the automatic

speed control system in automobiles. The main reviews are as follows:

2.1 THE FUNDAMENTAL OF SENSOR

Sensor is an electrical device that maps an environmental attribute to a

quantitative measurement. It is created to collect information about the world. Each

sensor is based on a transduction principle which is conversion of energy from one

form to another form. The infra red transmitter produces infra red signal. These

signals are propagated through a sensing medium and the receiver can be used to

detect returning signals. In most applications, the sensing medium is simply air. An

infra red sensor typically comprises atleast one infra red transducer which transforms

electrical energy into sound and in reverse sound into electrical energy, an electrical

connection and optionally, an electronic circuit for signal processing also enclosed.

2.2 TARGET ANGLE

This term refers to the "tilt response" limitations of a given sensor. Since Infra

red waves reflect off the target object, target angles indicate acceptable amounts of tilt

for a given sensor.

2.3 BEAM SPREADThis term is defined as the area in which a round wand will be sensed if passed

through the target area. This is the maximum spreading of infra red as it leaves the

transducer.

2.4 ENVIRONMENTAL FACTORS EFFECT TO INFRA RED SENSOR

PERFORMANCE

2.4.1 TemperatureThe velocity of sound in air is 13,044 in./s at 0 C, it is directly proportional to



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air temperature. As the ambient air temperature increases, the speed of sound also

increases. Therefore if a fixed target produces an echo after a certain time delay, and if

the temperature drops, the measured time for the echo to return increases, even though

the target has not moved. This happens because the speed of sound decrease returning

an echo more slowly than at the previous, warmer temperature. If varying ambient

temperatures are expected in a specific application, compensation in the system for the

change in sound speed is recommended.

2.4.2 Air Turbulence and Convection Currents

A particular temperature problem is posed by convection currents that contain

many bands of varying temperature. If these bands pass between the sensor and the

target, they will abruptly change the speed of sound while present. No type of

temperature compensation (either temperature measurement or reference target) will

provide complete high-resolution correction at all times under these circumstances. In

some applications it may be desirable to install shielding around the sound beam to

reduce or eliminate variations due to convection currents. Averaging the return times

from a number of echoes will also help reduce the random effect of convection

currents. Users addressing applications requiring high accuracy and resolution should

evaluate these suggestions carefully.

2.4.3 Atmospheric Pressure

Normal changes in atmospheric pressure will have little effect on measurement

accuracy. Reliable operation will deteriorates however, in areas of unusually low air

pressure, approaching a vacuum.

2.4.4 Humidity

Humidity does not significantly affect the operation of an infra red measuring

system. Changes in humidity do have a slight effect, however, on the absorption of

sound. If the humidity produces condensation, sensors designed to operate when wet

must be used.



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2.4.5 Acoustic Interference

Special consideration must be given to environments that contain background

noise in the infra red frequency spectrum. When in close proximity to a sensor,

whether directed at the sensor or not, infra red noise at or around the sensor's

frequency may affect system operation. Typically, the level of background noise is

lower at higher frequencies, and narrower beam angles work best in areas with a high

infra red background noise level. Often a baffle around the noise source will eliminate

the problem. Because each application differs, testing for interference is suggested.

2.4.6 Splashing Liquids

Splashing liquids should be kept from striking the surface of the sensor, both

to protect the sensor from damage if it is not splash proof and to ensure an open path

for the sound energy to travel.

2.5 SENSOR’S TARGET CONSIDERATIONS

2.5.1 Composition

Nearly all targets reflect infra red waves and therefore produce an echo that

can be detected. Some textured materials produce a weaker echo, reducing the

maximum effective sensing range. The reflectivity of an object is often a function of

frequency. Lower frequencies can have reduced reflections from some porous targets,

while higher frequencies reflect well from most target materials. Precise performance

specifications can often be determined only through experimentation.

2.5.2 Shape

A target of virtually any shape can be detected, if sufficient echo returns to the

sensor. Targets that are smooth, flat, and perpendicular to the sensor's beam produce

stronger echoes than irregularly shaped targets. A larger target relative to sound wave-

length will produce a stronger echo than a smaller target until the target is larger than

approximately 10 wavelengths across. Therefore, smaller targets are better detected

with higher frequency sound. In some applications a specific target shape such as a

sphere, cylinder, or internal cube corner can solve alignment problems between the

sensor and the target.



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2.5.3 Target Orientation to Sensor

To produce the strongest echoes, the sensor's beam should be pointed toward

the target. If a smooth, flat target is inclined off perpendicular, some of the echo is

deflected away from the sensor and the strength of the echo is reduced. Targets that

are smaller than the spot diameter of the transducer beam can usually be incline more

than larger targets. Sensors with larger beam angles will generally produce stronger

echoes from flat targets that are not perpendicular to the axis of the sound beam.

Sound waves striking a target with a coarse, irregular surface will diffuse and reflect

in many directions. Some of the reflected energy may return to the sensor as a weak

but measurable echo. As always, target suitability must be evaluated for each

application.



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CHAPTER 3

METHODS AND METHODOLOGY

Fig 3.1 Block Diagram

3.1 IR RANGING CIRCUIT

For this circuit, it can be divided into several parts, which are process to produced

infra red wave part, transmitter part, receiver part and lastly output part.

3.1.1 Transmitter

The supply circuit is needed to supply a short 10μs pulse to the trigger input to

start the ranging. The sensor will send out a cycle of burst of infra red and raise its



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echo line high. It then listens for an echo, and as soon as it detects one it lowers the

echo line again. The echo line is therefore a pulse whose width is proportional to the

distance to the object. By timing the pulse it is possible to calculate the range in

inches/centimeters or anything else. If nothing is detected then the sensor will lower

its echo line anyway.

Before transmit the infra red wave, there is a part which is infra red wave

generator that function to generate infra red wave. After infra red wave was produced,

infra red transmitter transmits the infra red waves toward a road surface to find out the

obstacle. The range that obstacle detected is depends on the range of infra red sensors

that used.

3.1.2 Receiver

The receiver is a classic two stage op-amp circuit, which locks some residual

DC which always seems to be present. It takes up the infra red coming from the

obstacle. The output of the amplifier is fed into an 358 comparator IC. If the infra red

wave is detects the obstacle, it will produce a reflected wave. An infra red receiver is

used for receiving the infra red waves reflected from the road surface to generate a

reception signal. There is infra red transducer that will transform back the incident

wave to electrical energy. This signal amplified by an amplifier. The amplified signal

is compared with reference signal to detect components in the amplified signal due to

obstacles on the road surface. The magnitude of the reference signal or the

amplification factor of the amplifier is controlled to maintain a constant ratio between

the average of the reference signal and the average of the amplified signal.



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Fig 3.2 IR transmitter and reciever

3.1.3 Operation

In operation, the processor waits for an active low trigger pulse to come in

After a while, the returning echo will be detected and the echo line will be lowered.

The width of this pulse represents the flight time of the ir burst. If no echo is detected

then it will automatically time out.

The process of Integration Hardware and Software is very important because

the of interface the software and hardware is so hard. Although, the simulations will

right output, it is not perfect for the real situation. The problem will exist after we try

to interface both. So, doing analysis is compulsory to correct the software or hardware

so that we can get the right result.

Figure 3.1 shows block diagram for development of this project. Once, the title

of this project Automatic Speed Control System in Automobiles, the identifying and

understanding process was done. In this process, I found out all notes and information

related to the project. The process was divided into two main groups which are

software and hardware development. For the software development, LabVIEW



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software is used. Therefore all programming must suitable and match with this

controller. The process of software development is continuously done until get the

perfect resulted.

For the hardware development, the focus is to develop the circuit and board for

LabVIEW software. Besides, focus is to connect infra red circuit and DC motor to

implement to this project. After that, we must do the connection between infra red

sensor, LabVIEW and lastly motor for the output.



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CHAPTER 4

SIGNIFICANCE OF THE PROJECT

1) Nowadays the usage of vehicles is increasing in a tremendous way.

As the technology has advanced and as the population has increased the

number of vehicles has increased in a tremendous way, these lead to many

problems like rash driving rough driving and traffic jam. There is a

requirement of a speed control system to get rid of these problems.

2) The number of road accidents is hiking.

There are a lot of accidents happening due to the carelessness of the driver or

due to many other reasons the automatic speed control system can limit the occurrences

of these accidents .To avoid accidents ,there is the requirement of a speed control system

that control motor speed when the vehicles are closer than a limit.

This project is designed to develop a new system that can solve this problem

where drivers may not control speed manually but the vehicles can stop automatically

due to obstacles. This project is about a system that can control speed for safety. Using

infer red as a ranging sensor, its function based on infer red wave. After transmit by

transmitter, the wave can reflect when obstacle is detected and is received by the

receiver.



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4.1 MAIN PARTS OF THE PROJECT

1 ) DISTANCE SENSING IR SENSOR

2) PROCESSING USING LAB VIEW

3) SPEED CONTROL OF DC MOTOR



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CHAPTER 5

IR SENSOR

Infra red light is electromagnetic waves with longer wavelengths than

those of visible light, extending from the nominal red edge of the visible

spectrum at 0.74 micrometers (µm) to 300 µm. This range of wavelengths

corresponds to a frequency range of approximately 1 to 400 THz, and includes

most of the thermal radiation emitted by objects near room temperature.

Infrared light is emitted or absorbed by molecules when they change the

irrotational-vibrational movements.

An infrared sensor is a device (usually with supporting circuitry) that

can detect infrared light (which is below the optical spectrum) for use to a

purpose. Most of the remote controls for TVs and other entertainment

equipment use infrared energy as the transmission medium to carry

information between the control and the equipment to be operated. Infrared

sensors also have important scientific, military, security and rescue

applications since they can "see" the "radiant heat energy" which is infrared

radiation. This electromagnetic energy is in the wavelengths from about 750

nm, which is the lower end of the optical spectrum, to well over 10,000 nm,

deep in the infrared. The "heart" of the system per the question is a photo

detector or photo sensor. And it does its thing based on black body radiation,

which it the emission of energy based on the temperature of the object. As the

radiant energy is a direct function of temperature, even the slightest difference

in temperature results in the radiation of a slightly different wavelength of

infrared light. (A little hotter, a higher frequency or shorter wavelength - more

toward visible light). A little cooler and the opposite effect follows.) The

infrared radiation falls on the sensor (there are a bunch of different kinds, and a

range of operating frequencies and bandwidths depending on application) and,

through photoelectric effect, changes the "nature" of the chemistry/physics of

the photosensitive material. This is seen by supporting electronics as a change

http://en.wikipedia.org/wiki/Wavelength

http://en.wikipedia.org/wiki/Light

http://en.wikipedia.org/wiki/Red

http://en.wikipedia.org/wiki/Visible_spectrum


http://en.wikipedia.org/wiki/Micrometre

http://en.wikipedia.org/wiki/Frequency_spectrum

http://en.wikipedia.org/wiki/THz

http://en.wikipedia.org/wiki/Thermal_radiation

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Infrared_spectroscopy

http://en.wikipedia.org/wiki/Infrared_spectroscopy

http://en.wikipedia.org/wiki/Molecule

http://en.wikipedia.org/wiki/Thermal_radiation

http://en.wikipedia.org/wiki/THz

http://en.wikipedia.org/wiki/Frequency_spectrum

http://en.wikipedia.org/wiki/Micrometre



http://en.wikipedia.org/wiki/Red

http://en.wikipedia.org/wiki/Light

http://en.wikipedia.org/wiki/Wavelength



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of resistance which changes current or voltage in the circuitry according to the

way it was designed.

Fig 5.1 IR Sensor

Table 5.1 IR Sensor PIN connection

PIN CONNECTION DESCRIPTION

1 OUTPUT DIGITAL OUTPUT

2 VCC CONNECTION TO

CIRCUIT SUPPLY

3 GROUND CONNECTION TO

CIRCUIT GROUND

5.1 FEATURES

This is a multipurpose infrared sensor which can be used for obstacle sensing,

color detection (between basic contrasting colours), fire detection, line sensing, etc



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and also as an encoder sensor. The sensor provides a digital and an analog output. The

sensor outputs a logic one (+5V) at the digital output when an object is placed in front

of the sensor and a logic zero (0V), when there is no object in front of the sensor. An

onboard LED is used to indicate the presence of an object. The sensor outputs an

analog voltage between 0V and 5V, corresponding the distance between the sensor

and the object at the analog output. The analog output can be hooked to an ADC to get

the approximate distance of the object from the sensor. IR sensors are highly

susceptible to ambient light and the IR sensor on this sensor is suitably. covered to

reduce effect of ambient light on the sensor. The sensor has a maximum range of

around 40-50 cm indoors and around 15-20 cm outdoors. Operating voltage: 3 to 9V

(Range maximum for 9V). The module consists of 358 comparator IC. The output of

sensor is high whenever it IR frequency and low otherwise. The on-board LED

indicator helps user to check status of the sensor without using any additional

hardware. The power consumption of this module is low. It gives a digital output.

(varies with

surrounding light conditions)

holes of 3mm diameter for easy mounting.

5.2 USING THE SENSOR

The sensor has a simple 4 pin interface – > +V(5V), Gnd, Digital Out and

Analog Out. The sensor can operate within an operating voltage of 4 to 9V. The input

power should be provided to the +V (Vcc) and the Gnd pin. The digital output of the

sensor is provided on the third pin – Dout. The analog output of the sensor is provided

on the third pin – A out. Once the sensor is powered up, you will have to calibrate the

sensor for the specific environment it will be used in. To calibrate the sensor, you will

have to set the potentiometer by turning its knob by hand or a screw driver. You will

have to power the sensor and rotate the knob of the potentiometer until the output of

the sensor changes from high to low.

The sensitivity of the IR Sensor is tuned using the potentiometer. The

potentiometer is tuneable in both the directions. Initially tune the potentiometer in



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clockwise direction such that the Indicator LED starts glowing. Once that is achieved,

turn the potentiometer just enough in anti-clockwise direction to turn off the Indicator

LED. At this point the sensitivity of the receiver is maximum. Thus, its sensing

distance is maximum at this point. If the sensing distance (i.e., Sensitivity) of the

receiver is needed to be reduced, then one can tune the potentiometer in the anti-

clockwise direction from this point. Further, if the orientation of both Tx and Rx

LED’s is parallel to each other, such that both are facing outwards, then their

sensitivity is maximum. If they are moved away from each other, such that they are

inclined to each other at their soldered end, then their sensitivity reduces. Tuned

sensitivity of the sensors is limited to the surroundings. Once tuned for a particular

surrounding, they will work perfectly until the IR illumination conditions of that

region nearly constant. For example, if the potentiometer is tuned inside

room/building for maximum sensitivity and then taken out in open sunlight, its will

require retuning, since sun’s rays also contain Infrared (IR) frequencies, thus acting as

a IR source (transmitter). This will disturb the receiver’s sensing capacity. Hence it

needs to be retuned to work perfectly in the new surroundings. The output of IR

receiver goes low when it receives IR signal. Hence the output pin is normally low

because, though the IR LED is continuously transmitting, due to no obstacle, nothing

is reflected back to the IR receiver. The indication LED is off. When an obstacle is

encountered, the output of IR receiver goes low, IR signal is reflected from the

obstacle surface. This drives the output of the comparator low. This output is

connected to the cathode of the LED, which then turns ON.

5.3 APPLICATION

• Obstacle detection

• Shaft encoder

• Fixed frequency detection

5.4 COMPARATOR IC LM358

The LM158 series consists of two independent, high gain, internally frequency

compensated operational amplifiers which were designed specifically to operate from



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a single power supply over a wide range of voltages. Operation from split power

supplies is also possible and the low power supply current drain is independent of the

magnitude of the power supply voltage. Application areas include transducer

amplifiers, dc gain blocks and all the conventional op amp circuits which now can be

more easily implemented in single power supply systems. For example, the LM158

series can be directly operated off of the standard +5V power supply voltage which

is used in digital systems and will easily provide the required interface electronics

without requiring the additional ±15V power supplies. The LM358 and LM2904 are

available in a chip sized package (8-Bump micro SMD) using National’s micro SMD

package technology.

5.4.1Unique Characteristics

In the linear mode the input common-mode voltage range includes ground and

the output voltage can also swing to ground, even though operated from only a single

power supply voltage. The unity gain cross frequency is temperature compensated.

The input bias current is also temperature compensated.

5.4.2 Features

o Available in 8-Bump micro SMD chip sized package,

o Internally frequency compensated for unity gain

o Large dc voltage gain: 100 dB

o Wide bandwidth (unity gain): 1 MHz (temperature compensated)

o Wide power supply range:

— Single supply: 3V to 32V

— or dual supplies: ±1.5V to ±16V

o Very low supply current drain (500 μA)— essentially independent of supply

voltage

o Low input offset voltage: 2 mV

o Input common-mode voltage range includes ground

o Differential input voltage range equal to the power supply voltage

o Large output voltage swing



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5.5 POTENTIOMETER CA6

6mm carbon potentiometers with plastic housing and protection type IP

5 (dust-proof). CA6 potentiometers are available both in through-hole and in

SMD terminal configuration. The substrate in SMD potentiometers is high

temperature resistant, for reflow soldering. Tapers available include linear, log

and antilog, even for SMD potentiometers. ACP can also study special requests.

Terminals are manufactured in tinned brass to guarantee better soldering and

higher resistance to corrosion. They can be provided straight or crimped (with

―snap in‖), which is recommended to hold the potentiometer to the board prior

to the soldering operation. Thumbwheels and shafts can be provided either

separately or already inserted in the potentiometer. CA6VSMD potentiometers,

with or without thumbwheel, can be requested in Bulk or Tape & Reel (T&R)

packaging. ACP’s potentiometers can be adjusted from either side, both in the

horizontal and the vertical adjustment types. There is a guide on the housing to

simplify the manual adjusting operations. Our potentiometers can be

manufactured in a wide range of possibilities regarding:

o Resistance value.

o Tolerance.

o Tapers / variation laws of the resistive element (linear, log, antilog).

o Others on request.

o Pitch.

o Positioning of the wiper (the standard is at 50%).

o Housing and rotor color.

o Mechanical life.

o Self-extinguishable plastic parts according to UL 94 V-0.



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Fig 5.2 Carbon Potentiometers

5.5.1 Applications

o Small electronic appliances.

o Measurement and test equipment.

o Automotive: alarms, switches

o Telecommunication equipment (antenna amplifiers and receivers, video

communication, intercommunication.)

o Alarm system



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Fig 5.3 Some models of CA6

5.5.2 Modifications of CA6

o CA9-Carbon potentiometer CA

o CE9-Cermet potentiometer CE



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CHAPTER 6

DC MOTORS

Almost every mechanical movement that we see around us is

accomplished by an electric motor. Electric machines are a means of converting

energy. Motors take electrical energy and produce mechanical energy. Electric

motors are used to power hundreds of devices we use in everyday life. Electric

motors are broadly classified into two different categories: DC (Direct Current)

and AC (Alternating Current). Within these categories are numerous types, each

offering unique abilities that suit them well for specific applications. In most

cases, regardless of type, electric motors consist of a stator (stationary field) and

a rotor (the rotating field or armature) and operate through the interaction of

magnetic flux and electric current to produce rotational speed and torque. DC

motors are distinguished by their ability to operate from direct current. There are

different kinds of D.C. motors, but they all work on the same principles.

Fig 6.1 A DC Motor



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6.1 23ELECTROMECHANICAL ENERGY CONVERSION

An electromechanical energy conversion device is essentially a medium of

transfer between an input side and an output side. Three electrical machines (DC,

induction and synchronous) are used extensively for electromechanical energy

conversion. Electromechanical energy conversion occurs when there is a change in

magnetic flux linking a coil, associated with mechanical motion.

6.1.1 Electric Motor

The input is electrical energy (from the supply source), and the output is

mechanical energy (to the load).

Fig 6.2 Electric motor

6.1.2 Electric Generator

The Input is mechanical energy (from the prime mover), and the output is

electrical energy.

Fig 6.3 Electric Generator



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6.2 PRINCIPLE OF OPERATION

Consider a coil in a magnetic field of flux density B (figure 4). When the two

ends of the coil are connected across a DC voltage source, current I flows through it.

A force is exerted on the coil as a result of the interaction of magnetic field and

electric current. The force on the two sides of the coil is such that the coil starts to

move in the direction of force.

In an actual DC motor, several such coils are wound on the rotor, all of which

experience force, resulting in rotation. The greater the current in the wire, or the

greater the magnetic field, the faster the wire moves because of the greater force

created. At the same time this torque is being produced, the conductors are moving in

a magnetic field. At different positions, the flux linked with it changes, which causes

an emf to be induced. This voltage is in opposition to the voltage that causes current

flow through the conductor and is referred to as a counter-voltage or back emf.

Fig 6.4 Torque production in a DC motor



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Fig 6.5 Induced voltage in the armature winding of DC motor

The value of current flowing through the armature is dependent upon the

difference between the applied voltage and this counter-voltage. The current due to

this counter-voltage tends to oppose the very cause for its production according to

Lenz’s law. It results in the rotor slowing down. Eventually, the rotor slows just

enough so that the force created by the magnetic field ( F = Bil ) equals the load force

applied on the shaft. Then the system moves at constant velocity. The same DC

machine can be used either as a motor or as a generator, by reversing the terminal

connections.

6.3 DC MOTOR EQUIVALENT CIRCUIT

The schematic diagram for a DC motor is shown below. A DC motor has two

distinct circuits: Field circuit and armature circuit. The input is electrical power and

the output is mechanical power. In this equivalent circuit, the field winding is supplied

from a separate DC voltage source of voltage Vf. Rf and Lf represent the resistance

and inductance of the field winding. The current If produced in the winding

establishes the magnetic field necessary for motor operation. In the armature (rotor)

circuit, VT is the voltage applied across the motor terminals, I a is the current flowing

in the armature circuit, Ra is the resistance of the armature winding, and Eb is the total

voltage induced in the armature.



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Fig 6.6 Equivalent Circuit

6.4 ELECTRIC BRAKING

Sometimes it is desirable to stop a d.c. motor quickly. This may be necessary

in case of emergency or to save time if the motor is being used for frequently repeated

operations. The motor and its load may be brought to rest by using either (i)

mechanical (friction) braking or (ii) electric braking. In mechanical braking, the motor

is stopped due to the friction between the moving parts of the motor and the brake

shoe i.e. kinetic energy of the motor is dissipated as heat. Mechanical braking has

several disadvantages including non-smooth stop and greater stopping time. In electric

braking, the kinetic energy of the moving parts (i.e., motor) is converted into electrical

energy which is dissipated in a resistance as heat or alternativley, it is returned to the

supply source (Regenerative braking). For DC shunt as well as series motors, thefollowing three methods of electric braking are used:

(i) Rheostatic or Dynamic braking

(ii) Plugging

(iii) Regenerative braking

It may be noted that electric braking cannot hold the motor stationary and

mechanical braking is necessary. However, the main advantage of using electric



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braking is that it reduces the wear and tear of mechanical brakes and cuts down the

stopping time considerably due to high braking retardation.

6.4.1 Rheostatic or Dynamic braking

In this method, the armature of the running motor is disconnected from the

supply and is connected across a variable resistance R. However, the field winding is

left connected to the supply. The armature, while slowing down, rotates in a strong

magnetic field and, therefore, operates as a generator, sending a large current through

resistance R. This causes the energy possessed by the rotating armature to be

dissipated quickly as heat in the resistance. As a result, the motor is brought to

standstill quickly. Fig(7.6) shows dynamic braking of a shunt motor. The braking

torque can be controlled by varying the resistance R. If the value of R is decreased as

the motor speed decreases, the braking torque may be maintained at a high value. At a

low value of speed, the braking torque becomes small and the final stopping of the

motor is due to friction. This type of braking is used extensively in connection with

the control of elevators and hoists and in other applications in which motors must be

started, stopped and reversed frequently.

Fig 6.7 Dynamic braking



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6.4.2 Plugging

In this method, connections to the armature are reversed so that motor tends to

rotate in the opposite direction, thus providing the necessary braking effect. When the

motor comes to rest, the supply must be cut off otherwise the motor will start rotating

in the opposite direction.

Fig (7.7)shows plugging of a d.c. shunt motor. Note that armature connections

are reversed while the connections of the field winding are kept the same. As a result

the current in the armature reverses. During the normal running of the motor ,the back

e.m.f. E b opposes the applied voltage V. However, when armature connections are

reversed, back e.m.f. E b and V act in the same direction around the circuit. Therefore,

a voltage equal to V + E b is impressed across the armature circuit. Since E b ~ V, the

impressed voltage is approximately 2V. In order to limit the current to safe value, a

variable resistance R is inserted in the circuit at the time of changing armature

connections.

Fig 6.8 Plugging



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6.4.3 Regenerative braking

In the regenerative braking, the motor is run as a generator. As a result, the

kinetic energy of the motor is converted into electrical energy and returned to the

supply. Fig.(5.15) shows two methods of regenerative braking for a shunt motor.

Fig 6.9 Regenarative braking

In first method, field winding is disconnected from the supply and field current

is increased by exciting it from another source [See Fig. 7.8 (i)]. As a result, induced

e.m.f. E exceeds the supply voltage V and the machine feeds this energy into the

supply. Thus braking torque is provided upto the speed at which induced e.m.f. and

supply voltage are equal. As the machine slows down, it is not possible to maintain

induced e.m.f. at a higher value than the supply voltage. Therefore, this method is

possible only for a limited range of speed.

In second method, the field excitation does not change but the load causes

the motor to run above the normal speed (e.g., descending load on a crane). As a

result, the induced e.m.f. E becomes greater than the supply voltage V [See Fig. 7.8

(ii)]. The direction of armature current I, therefore, reverses but the direction of shunt

field current If remains unaltered. Hence the torque is reversed and the speed falls

until E becomes less than V.



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6.5 Necessity of D.C. Motor Starter

At starting, when the motor is stationary, there is no back e.m.f. in the

armature. Consequently, if the motor is directly switched on to the mains, the

armature will draw a heavy current (Ia = V/R a) because of small armature resistance.

As an example, 5 H.P., 220 V shunt motor has a full-load current of 20 A and an

armature resistance of about 0.5 W. If this motor is directly switched on to supply, it

would take an armature current of 220/0.5 = 440 A which is 22 times the full-load

current. This high starting current may result in:

(i) burning of armature due to excessive heating effect,

(ii) damaging the commutator and brushes due to heavy sparking,

(iii) excessive voltage drop in the line to which the motor is connected.

The result is that the operation of other appliances connected to the line may

be impaired and in particular cases, they may refuse to work. In order to avoid

excessive current at starting, a variable resistance (known as starting resistance) is

inserted in series with the armature circuit. This resistance is gradually reduced as the

motor gains speed (and hence E b increases) and eventually it is cut out completely

when the motor has attained full speed. The value of starting resistance is generally

such that starting current is limited to 1.25 to 2 times the full-load current.



29

CHAPTER 7

L293 MOTOR DRIVER

The L293 is an integrated circuit motor driver that can be used for

simultaneous, bidirectional control of two small motors. Small means small. The

L293 is limited to 600 mA, but in reality can only handle much small currents unless

you have done some serious heat sinking to keep the case temperature down. To

check for its working, hook up the circuit and run your motor while keeping your

finger on the chip. If it gets too hot to touch, you can't use it with your motor. The

L293 comes in a standard 16-pin, dual-in line integrated circuit package. The pinout

for the L293 in the 16-pin package is shown in top view. Pin 1 is at the top left when

the notch in the package faces up. Note that the names for pin functions may be

slightly different than what is shown in the following diagram.



30

Fig7.1 Pin number of L293 Motor Driver IC

The following schematic shows how to connect the L293 to your motor and

the PIC. Each motor takes 2 PIC pins. Here is a table describing the control pin

functions. Note that the enable pin is always high when the motor runs so we can

simply pull it high on the circuit board and then it will not take up 2 extra PIC pins.

Table 7.1 L293 Connections

Enable DIRA DIRB Function

H H L Turn right

H L H Turn left

H L/H H/L Fast stop

L either either Slow stop



31

Notes

1. You can save on some Stamp pins by connecting the Enable pin to +5V and just

using the direction pins to change directions and turn the motor on and off. Thatmeans you only need two PIC pins per motor. Put one pin high and the other low for

one direction, reverse the state of the pins for the other direction and put both pins low

to turn the motor off.

2. Remember to put your finger on top of the L293 when running the motor to see if

it is getting too hot.

3. The L293 ground goes to both the battery minus and to the PIC GND

4. The L293 has an automatic thermal shutdown which means the chip will stop

working if it gets too hot.

5. You can also use the L293 to drive relays and solenoids. Just connect the relay coil

to solenoid between one of the driver outputs (pins 3, 6, 11, or 14) and ground and

turn it on or off with the control pin (pins 2, 7, 10, 15). This is handy because you

could run one bidirectional motor and two relays using just 4 Stamp pins and a single

L293.



32

CHAPTER 8

SOFTWARE IMPLEMENTATION

Speed controlling is implemented using software LabVIEW of version

2010, developed by National Instuments(NI).

8.1 GETTING STARTED WITH LABVIEW VIRTUAL INSTRUMENTS

LabVIEW programs are called virtual instruments, or VIs, because their

appearance and operation imitate physical instruments, such as oscilloscopes and

multimeters. LabVIEW contains a comprehensive set of tools for acquiring,

analyzing, displaying, and storing data, as well as tools to help you troubleshoot code

you write. In LabVIEW, you build a user interface, or front panel, with controls and

indicators. Controls are knobs, push buttons, dials, and other input mechanisms.

Indicators are graphs, LEDs, and other output displays. After you build the front

panel, you add code using VIs and structures to control the front panel objects. The

block diagram contains this code.

We can use LabVIEW to communicate with hardware such as data acquisition,

vision, and motion control devices, as well as GPIB, PXI, VXI, RS232, and RS485

instruments.

8.2 BUILDING A VIRTUAL INSTRUMENT

In the following exercises, it will build a VI that generates a signal and

displays that signal in a graph. After completing the exercises, the front panel of the

VI will look similar to the front panel in the following figure.



33

Fig 8.1 Front panel of an example

8.3 LAUNCHING LabVIEW

The Getting Started window appears when you launch LabVIEW. Use this

window to create new projects and open existing files. You also can access resources

to expand the capability of LabVIEW and information to help you learn about

LabVIEW. The Getting Started window disappears when you open an existing file or

create a new file and reappears when you close all open front panels and block

diagrams. You also can display the window from the front panel or block diagram by

selecting View»Getting Started Window.

8.3.1 Opening a New VI from a Template

Panel objects you need to get started building common measurement

applications. Complete the following steps to create a VI that generates a signal and

displays it in the front panel window.

1. Launch LabVIEW.

2. Select File»New to display the New dialog box.



34

3. From the Create New list, select VI»From Template»Tutorial (Getting Started)»

Generate and Display. This template VI generates and displays a signal. A preview

and a brief description of the template VI appear in the Description section. The

following figure shows the New dialog box and the preview of the Generate and

Display template VI.

Fig 8.2 Openning a VI from a template

4. Click the OK button to create a VI from the template. You also can double-click the

name of the template VI in the Create New list to create a VI from a template.

LabVIEW displays two windows: the front panel window and the block diagram

window.



35

5. Examine the front panel window. The user interface, or front panel, appears with a

gray background and includes controls and indicators. The title bar of the front panel

indicates that this window is the front panel for the Generate and Display VI.

6. Select Window»Show Block Diagram and examine the block diagram of the

VI. The block diagram appears with a white background and includes VIs and

structures that control the front panel objects. The title bar of the block diagram

indicates that this window is the block diagram for the Generate and Display VI.

7. On the front panel toolbar, click the Run button, shown below. You also can press

the <Ctrl-R> keys to run a VI.

Fig 8.3 Run button

A sine wave appears on the graph in the front panel window.

8. Stop the VI by clicking the front panel STOP button, shown below.

Fig 8.4 Stop button

8.3.2 Adding a Control to the Front Panel

Front panel controls simulate the input mechanisms on a physical instrument

and supply data to the block diagram of the VI. Many physical instruments have

knobs you can turn to change an input value. Complete the following steps to add a

knob control to the front panel.

Tip: Throughout these exercises, you can undo recent edits by selecting

Edit»Undo or pressing the <Ctrl-Z> keys.

1. If the Controls palette, shown in Figure 1-3, is not visible in the front panel

window, select View»Controls Palette.

Tip: You can right-click any blank space in the front panel or the block diagram to

display a temporary version of the Controls or Functions palette. The Controls or

Functions palette appears with a thumbtack icon in the upper left corner. Click the

thumbtack to pin the palette so it is no longer temporary.



36

2. If you are a new LabVIEW user, the Controls palette opens with the Express

palette, shown in the following figure, visible by default. If you do not see the Express

palette, click Express on the Controls palette to display the Express palette.

Fig 8.5 Control palletes

3. Move the cursor over the icons on the Express palette to locate the Numeric

Controls palette. When you move the cursor over icons on the Controls palette, the

name of the sub palette, control, or indicator appears in a tip strip below the icon.

Some palette objects display a short name on the palette that is different from the

name that appears in the tip strip. The short name abbreviates the name of the palette

object so that it fits in the space available on the palette. If you have difficulty finding

a palette object by its short name, use the Search button on the Controls or Functions

palette to find the palette object by name.

4. Click the Numeric Controls icon to display the Numeric Controls palette.

5. Click the Knob control on the Numeric Controls palette to attach the control to the

cursor, and then add the knob to the front panel to the left of the waveform graph.

6. Select File»Save As and save the VI as Acquiring a Signal.vi in an easily

accessible.



37

8.3.3 Wiring Objects on the Block Diagram

To use the knob to change the amplitude of the signal, you must connect two

objects on the block diagram. Complete the following steps to wire the knob to the

Amplitude input of the Simulate Signal Express VI.

1. On the block diagram, move the cursor over the Knob terminal, show below.

Fig 8.6 Knob Terminal

The cursor becomes an arrow, or the Positioning tool, shown below. Use the

Positioning tool to select, position, and resize objects. You can resize only

loops and structures on the block diagram. Go to the front panel to resize

objects you have added to the front panel.

2. Use the Positioning tool to select the Knob terminal and make sure it is to the left

of the Simulate Signal Express VI and inside the gray loop, shown below.

Fig 8.7 while loop

The terminals inside the loop are representations of front panel controls and

indicators. Terminals are entry and exit ports that exchange information between the

front panel and block diagram.

3. Deselect the Knob terminal by clicking a blank space on the block diagram. If you

want to use a different tool with an object, you must deselect the object to switch thetool.

4. Move the cursor over the arrow on the Knob terminal, shown below

Fig 8.8 Start of a wiring



38

The cursor becomes a wire spool, or the Wiring tool, shown below. Use the Wiring

tool to wire objects together on the block diagram.

Fig 8.9 Wire bundle

5. When the Wiring tool appears, click the arrow on the Knob terminal and then click

the arrow on the Amplitude input of the Simulate Signal Express VI, shown below, to

wire the two objects together.

Fig 8.10 Wiring process

A wire appears and connects the two objects. Data flows along this wire from the

Knob terminal to the Express VI.

6. Select File»Save to save the VI.

8.3.4 Running a VI

Running a VI executes the solution. Complete the following steps to run the

Acquiring a Signal VI.

1. Display the front panel by pressing the <Ctrl-E> keys or by clicking the front panel.

2. Click the Run button or press the <Ctrl-R> keys to run the VI.

To indicate that the VI is running, the Run button changes to a darkened arrow, shown

below. You can change the value of most controls while a VI runs, but you cannot edit

the VI in other ways while the VI runs.



39

Fig 8.11 Run button

3. Move the cursor over the knob, hold the mouse button down, and turn the knob to

adjust the amplitude of the sawtooth wave. The amplitude of the sawtooth wave

changes as you turn the knob. As you change the amplitude, the cursor displays a tip

strip that indicates the numeric value of the knob. The y-axis on the graph scales

automatically to account for the change in amplitude.

4. Click the STOP button, shown below, to stop the VI.

Fig 8.12 STOP Button

The STOP button stops the VI after the loop completes its current iteration. The Abort

Execution button, shown below, stops the VI immediately, before the VI finishes the

current iteration. Aborting a VI that uses external resources, such as external

hardware, might leave the resources in an unknown state by not resetting or releasing

them properly. Design the VIs you create with a stop button to avoid this problem.

Fig 8.13 Designed stop button

8.3.5 Customizing a knob control

The knob control changes the amplitude of the sawtooth wave, so labelling it

Amplitude accurately describes the behaviour of the knob. Complete the following

steps to customize the appearance of the knob.

1. Right-click the front panel knob and select Properties from the shortcut menu to

display the Knob Properties dialog box. Click the Appearance tab to display the

Appearance page.

2. In the Label section on the Appearance page, delete the label Knob, and enter

Amplitude in the text box.



40

The Knob Properties dialog box should appear similar to the following figure.

Fig 8.14 Knob Properties dialog box

3. Click the Scale tab. In the Scale Style section, place a checkmark in the Show color

ramp checkbox. The knob in the front panel window updates to reflect these changes.

4. Click the OK button to save the current configuration and close the Knob Properties

dialog box.

5. Save 6. Reopen the Knob Properties dialog box and experiment with other

properties of the knob. For example, on the Scale page, try changing the colors for the

Marker text color by clicking the color box.

7. Click the Cancel button to avoid applying any changes you made while

experimenting. If you want to keep the changes you made, click the OK button the VI.

8.3.6 Opening a blank VI

If no template is available for the VI you want to build, you can start with a

blank VI and add Express VIs to accomplish a specific task. Complete the following

steps to open a blank VI.

1. In the Getting Started window, click the Create Project button to display the Create



41

Project dialog box. The Create Project dialog box provides common starting points for

LabVIEW projects.

2. Select Blank VI from the list of items and click Finish. A blank front panel window

and block diagram window appear.

3. Display the block diagram.

4. If the Functions palette is not visible, right-click any blank space on the block

diagram to display a temporary version of the Functions palette. Click the thumbtack,

shown below, in the upper left corner of the Functions palette to pin the palette so it is

no longer temporary.

Fig 8.15 Pin button

8.3.7 Configuring a VI to run continuously until the user stops it

In the current state, the VI runs once, generates one signal, and then stops

running. To run the VI until a condition occurs, you can use a While Loop. Complete

the following steps to add a While Loop to the block diagram.

1. Display the front panel and run the VI. The VI runs once and then stops. The front

panel does not have a stop button.

2. Display the block diagram.

3. Click the Search button, shown below, on the Functions palette, and enter While in

the text box. LabVIEW searches as you type the first few letters and displays any

matches in the search results text box.

Fig 8.16 Search button

If there are objects with the same name, use the information in the brackets to

the right of each object name to decide which object to select. Some objects are

located on multiple palettes because you can use them for multiple applications.



42

4. Double-click While Loop <<Execution Control>> to display the Execution Control

subpalette and temporarily highlight the While Loop on the subpalette.

5. Select the While Loop on the Execution Control palette.

6. Move the cursor to the upper left corner of the block diagram. Click and drag the

cursor diagonally to enclose all the Express VIs and wires, as shown in the following

figure.

Fig 8.17 Placing the While Loop around the Express Vis

7. Release the mouse to place the While Loop around the Express VIs and wires. The

While Loop, shown below, appears with a STOP button wired to the conditional

terminal. This While Loop is configured to stop when the user clicks the STOP

button.

Fig 8.18 While loop

8. Display the front panel and run the VI.

The VI now runs until you click the STOP button. A While Loop executes the VIs and

functions inside the loop until the user clicks the STOP button.



43

9. Click the STOP button and save the VI.

8.3.8 Using the error list window

If a VI contains an indicator you do not want to use, you can delete it.

Complete the following steps to remove the Mean indicator from the front panel.

1. Display the front panel and move the cursor over the Mean indicator until the

Positioning tool appears.

2. Click the Mean indicator, shown below, to select it and press the <Delete>

key.

Fig 8.19 Mean indicator

3. Display the block diagram. A wire appears as a dashed black line with a red X in

the middle, shown below. The dashed black line is a broken wire. The Run button,

shown below, appears broken to indicate the VI cannot run.

Fig 8.20 Broken wire

4. Click the broken Run button to display the Error list window. The Error list window

lists all errors in the VI and provides details about each error. You can use the Error

list window to locate errors.

5. In the errors and warnings list, select the Wire: has loose ends error and click the

Help button to display more information about the error.

6. In the errors and warnings list, double-click the Wire: has loose ends error to

highlight the broken wire.

7. Press the <Ctrl-B> keys to delete the broken wire. Pressing the <Ctrl-B> keys

deletes all broken wires on the block diagram. You can press the <Delete> key to

delete only the selected wire.

8. Select View»Error List to display the Error list window. No errors appear in the

errors and warnings field..



44

9. Click the Close button to close the Error list window. The Run button no longer

appears broken.

8.3.9 Controlling the speed of execution

To plot the points on the waveform graph more slowly, you can add a time

delay to the block diagram. Complete the following steps to control the speed at which

the VI runs.

1. On the block diagram, search for the Time Delay Express VI, shown below, on the

Functions palette and place it inside the While Loop.

Fig 8.21 Time delay

You can use the Time Delay Express VI to control the execution rate of the VI.

2. Enter 0.25 in the Time delay (seconds) text box. This time delay specifies how fast the loop

runs. With a 0.25 second time delay, the loop iterates once every quarter of a second.

3. Click the OK button to save the current configuration and close the Configure Time Delay

dialog box.

4. Display the front panel and run the VI.

5. Click the Enable switch and examine the change on the graph. If the Enable switch is on,

the graph displays the reduced signal. If the Enable switch is off, the graph does not display

the reduced signal.

6. Click the STOP button to stop the VI.

8.3.10 Time delay for execution

To plot the points on the waveform graphs more slowly, you can add a time

delay to the block diagram. A time delay slows the speed at which a VI runs.

Complete the following steps to control the speed at which the VI runs.

1. On the block diagram, search for the Time Delay Express VI.



45

2. Place the Time Delay Express VI inside the While Loop. The Configure Time

Delay dialog box appears.

3. Enter 1.000 in the Time delay (seconds) text box and click the OK button.

4. Display the front panel and run the VI. The VI runs more slowly. The loop iterates

once every second.

5. Stop the VI.

Another way to control the speed of the VI is to alter the rate of data acquisition. On

the block diagram, double click the Simulate Signal Express VI to display the

Configure Simulate Signal dialog box. Locate the Timing section in the dialog box.

The Timing section contains a number of ways to alter the rate of data acquisition and

the speed at which a VI runs.

For example, one of the default settings of the VI is Simulate Acquisition Timing.

This means that the VI mimics the acquisition rate of a hardware device. You can

select Run as fast as possible to display data more quickly. In the Samples per second

(Hz) text box, the default value is 1000, while the default value in the Number of

Samples text box is 100. This means that the VI will output 100 data points spanning

0.1 second. You can change these values to change the amount of data the VI

displays, as well as the rate at which the VI displays the data.



46

8.4 HARDWARE: ACQUIRING DATA AND COMMUNICATING WITH

INSTRUMENTS (WINDOWS)

LabVIEW has the capability to connect and interact with a large number of

hardware devices. Here we introduces you to two Express VIs that make acquiring

data and communicating with traditional, third-party instruments easier. Normally you

use the DAQ Assistant Express VI to acquire data with a DAQ device and data

acquisition hardware and that you have NI-DAQmx installed. use the NI Instrument

Driver Finder to find and install instrument drivers. To use the Instrument Driver

Finder, you must have Internet access. In the second exercise, you also use the

Instrument I/O Assistant Express VI to communicate with a traditional third party

instrument. This exercise requires an instrument and that you have the Instrument I/O

Assistant installed.

8.4.1 Acquiring a Signal in NI-DAQmx

You will use the DAQ Assistant Express VI to create a task in NI-DAQmx.

NI-DAQmx is a programming interface you can use to communicate with data

acquisition devices. In the Getting Started with LabVIEW»Getting Started with

DAQ»Taking an NI-DAQmx Measurement in LabVIEW book on the Contents tab in

the LabVIEW Help for information about additional ways to create NI-DAQmx tasks.

In the following exercises, you will create an NI-DAQmx task that continuously takes

a voltage reading and plots the data on a waveform graph.

8.4.2 Creating an NI-DAQmx Task

In NI-DAQmx, a task is a collection of one or more channels, which containstiming, triggering, and other properties. Conceptually, a task represents a

measurement or generation you want to perform. For example, you can create a task

to measure temperature from one or more channels on a DAQ device.

Complete the following steps to create and configure a task that reads a voltage level

from a DAQ device.

1. Open a new, blank VI.



47

2. On the block diagram, display the Functions palette and select Express»Input to

display the Input palette.

3. Select the DAQ Assistant Express VI, shown below, on the Input palette and place

it on the block diagram. The DAQ Assistant launches and the Create New Express

Task dialog box appears.

Fig 8.22 DAQ Assistant

4. Click Acquire Signals»Analog Input to display the Analog Input options.

5. Select Voltage to create a new voltage analog input task. The dialog box displays a

list of channels on each installed DAQ device. The number of channels listed depends

on the number of channels you have on the DAQ device.

6. In the Supported Physical Channels list, select the physical channel to which the

device connects the signal, such as ai0, and then click the Finish button. The DAQ

Assistant opens a new dialog box, shown in the following figure, that displays options

for configuring the channel you selected to complete a task.In the DAQ Assistant

dialog box select the Configuration tab and locate the Voltage Input Setup section.

8. Locate the Settings tab. In the Signal Input Range section, enter 10 for the Max

value and enter -10 for the Min value.

9. Locate the Timing Settings section at the bottom of the Configuration page. From

the Acquisition Mode pull-down menu, select N Samples.

10. Enter a value of 1000 in the Samples to Read text box.

11. Click the OK button to save the current configuration and close the DAQ

Assistant. LabVIEW builds the VI.



48

12. Save the VI as Read Voltage.vi in an easily accessible location.

Fig 8.23 Configuring a Task Using the DAQ Assistant



49

8.4.3 Making Signal Connections with NI myDAQ Setting up Your NI myDAQ

Device

Caution Insert and remove the 20-position screw terminal connector aligned

evenly to the NI myDAQ. Inserting the screw terminal connector at an angle to the NI

myDAQ may cause damage to the connector. The screw terminal connector must

snap securely into place to ensure proper signal connection.

Fig 8.24 NI myDAQ 20-Position Screw Terminal I/O Connector

The above figure shows the available audio, AI, AO, DIO, GND, and power

signals accessed through the 3.5 mm audio jacks and screw terminal connection signal

wires must be securely affixed and screwed down in the screw terminal connector to

ensure proper connection.

Fig 8.25 NI myDAQ Connection Diagram



50

Table 8.1 Configuring a Task Using the DAQ Assistant

8.4.4 Connecting analog input signals

When configuring the input channels and making signal connections, you must

first determine whether the signal sources are floating or ground referenced. The

following sections describe these two signal types.

8.4.4.1 Ground-Referenced Signal Sources

A ground-referenced signal source is connected to the building system ground,

so it is already connected to a common ground point with respect to the NI myDAQ

device, assuming that the computer is plugged into the same power system.

Instruments or devices with non isolated outputs that plug into the building power

system are ground-referenced signal sources. The difference in ground potential

between two instruments connected to the same building power system is typically

between 1 and 100 mV. This difference can be much higher if power distribution

circuits are improperly connected. If a grounded signal source is improperly

measured, this difference might appear as a measurement error. Connect the

differential analog inputs across the signal source and do not connect the NI myDAQ

AGND pin to the grounded source.



51

8.4.4.2 Floating Signal Sources

A floating signal source is not connected to the same ground reference as NI

myDAQ, but instead has an isolated reference point. Some examples of floating signal

sources are battery-powered devices, outputs of transformers, thermocouples, optical

isolator outputs, and isolation amplifiers. An instrument or device that has an isolated

output is a floating signal source. You must connect the ground reference of a floating

signal to an NI myDAQ AGND pin through a bias resistor or jumper wire to establish

a local or onboard reference for the signal. Otherwise, the measured input signal

varies as the source floats out of the common-mode input range.

8.4.5 NI myDAQ DMM Fuse Replacement

To replace a broken fuse, complete the following steps.

1. Power down the device by properly disconnecting it from the PC and removing the

USB cable.

2. Remove the screw terminal connector and all other signal cables from the device.

3. Loosen the four Phillips screws that attach the bottom of the enclosure to the

device, and remove the top lid of the enclosure

Fig 8.26 NI myDAQ Fuse Location



52

8.5 PROGRAM

Fig 8.27 Program



53

8.6 PROJECT PROTOYPE

Fig 8.28(a) Prototype

Fig 8.28(b) Prototype

8.7 USING NI myDAQ WITH LABVIEW

This section provides an overview of using NI myDAQ with LabVIEW. With

NI ELVISmx, the NI myDAQ instruments have an associated LabVIEW Express VI.

Express VIs allow you to interactively configure the settings for each instrument. This

enables you to develop LabVIEW applications without extensive programming

expertise. To access the NI ELVISmx Express VIs, open a LabVIEW block diagram

and select Measurement I/O»NI ELVISmx from the function palette. Table shows the

available NI ELVISmx Express VIs. To access help file, go to Start»All

Programs»National Instruments»NI ELVISmx for NI ELVIS & NI myDAQ»NI

ELVISmx Help.



54

Fig 8.29 NI ELVISmx Express VIs for NI myDAQ

CHAPTER 9

PROJECT ANALYSIS

9.1 ADVANTAGES OF IR SENSOR

o The power consumption is low.

o It gives a digital output.



55

o It has a maximum range of around 40-50 cm indoors and around 15-20

cm outdoors.

o Operating voltage: 3 to 9V

9.2 ADVANTAGES OF STEPPER MOTOR

o Have high holding torque -they have the property of being ―self locking‖

when the rotor is stationary.

o Directly compatible with digital control techniques(interfaced to a digital

Step\Direction controller, a microprocessor, or a computer).

o Exhibit excellent positioning accuracy, and errors are non-accumulating

o Motor construction is simple and rugged.

o There are usually only two bearings, and the motor generally has a long

maintenance-free life.

o It is a cost-effective actuator.

9.3 ADVANTAGE OF COMPARATOR IC LM358

o Two internally compensated op amps

o Eliminates need for dual supplies

o Allows direct sensing near GND and VOUT also goes to

o GND

o Compatible with all forms of logic

o Power drain suitable for battery operation

9.4 DISADVANTAGES

o Easily affected by noise.

o The IR sensor needs to be retuned in new surroundings for its perfect

working.



56

CHAPTER 10

CONCLUSION AND FUTURE SCOPE

A dc motor speed control system is developed by using National

Instrument’s Lab VIEW software and data acquisition. This technique saves

project development time.



57

So by using this system we can reduce rash driving and accidents up to

somewhat and we can save many lives and many valuable properties. We can

reduce the rash driving with in cities, with in the regions of school zones,

villages that are near to the high ways and beside the high ways. To make this

system activate we need speed breakers in more number where we supposed to

avoid rash driving. We can decrease the speed of the vehicle proportionately

by increasing number of speed breakers. So by using this system we are

reducing the upper limit of the speed of vehicle to a lower value for the

required time without altering any other thing.

10.1 FUTURE SCOPE

The project can be implemented by using an ultra sonic sensors. Then

the following advantages can be met:

o less interference between transmitted and received waves

o measures and detects distance to moving object

o not affected by dust, moist and temperature

REFERENCE

[1] R.Rajamani, Vehicles Dynamics and Control. New York:Springee-

Verlag,2006.

[2] M.S.Nise, Control Systems Engineering. Hobokon, N.J:Wiley,

2011, ch.4.



58

[3] S.Tsugawa.’’ Trends and Issues in safe driver assistance sytems,‖IATSS

Res, Vol.30,no2,PP.6-18,2006.

[4] D.J. Le Blane,R.J Kiefer,R.K Deering,M.A.Sheelman,M.D Palmer and

J.Salinger.‖Forward collision warning: preliminary requirement for crash alert

Timing‖.presented at the Soc. Automotive Eng. Con Warr endale

.P.A,.2001,paper 2001-01-0462

BIBLIOGRAPHY

1) Electromagnetic waves and radiating system- JORDAN – KEITH

and G. BALMANI

2) Automobile Engineering- KRIPAL SINGH

3) Thermal Engineering- YADAV



59

APPENDIX

Performance is typical after a three-minute warmup, at 23 °C unless otherwise specified. This

document may not contain the most recent published specifications. To get the most recent edition of

this document, go to ni.com/manuals and enter mydaq into the Search field.

Analog Input

Number of channels................................2 differential or 1 stereo audio input

ADC resolution.......................................16 bits

Maximum sampling rate .........................200 kS/s

Timing accuracy .....................................100 ppm of sample rate

Timing resolution ...................................10 ns Range



60

Analog input .........................................±10 V, ±2 V, DC-coupled

Audio input............................................±2 V, AC-coupled Passband ( – 3 dB)

Analog input .........................................DC to 400 kHz

Audio input...........................................1.5 Hz to 400 Kh Connector type

Analog input ........................................Screw terminals

Audio input...........................................3.5 mm stereo jackInput type (audio input) .......................Line-in or microphone

Microphone excitation (audio input) ......5.25 V through 10 k Absolute accuracy.

Input FIFO size.......................................4,095 samples, shared among channels used

Maximum working voltage for analog inputs (signal + common mode) .............±10.5 V to AGND

Common-mode rejection ratio (CMRR) (DC to 60 Hz)..................70 dBInput impedance Device on AI+ or AI – to AGND ...............>10 G || 100 pF AI+ to AI –

................................>10 G || 100 pF Device off AI+ or AI – to AGND ...............5 k

AI+ to AI – ................................10 k

Anti-aliasing filter...................................None Overvoltage protection AI+ or AI – to

AGND.............................±16 V

Overvoltage protection (audio input left and right)......................None

Analog Output

Number of channels................................2 ground-referenced or 1 stereo audio output

DAC resolution.......................................16 bits

Maximum update rate .............................200 kS/s Range



61

Analog output ..................................±10 V, ±2 V, DC-coupled

Audio output....................................±2 V, AC-coupled maximum output current

(analog output)1 ......................................2 mA

Output impedance

Analog output ................................. 1

Audio output ................................... 120 Minimum load impedance

(audio output) ......................................... 8 Connector typeAnalog output ................................. Screw terminalsAudio output ................................... 3.5 mm stereo jackAC-coupling high-pass frequency

(audio output with 32 load)................ 48 Hz

Slew rate................................................. 4 V/sTiming accuracy..................................... 100 ppm of sample rateTiming resolution................................... 10 nsOverdrive protection .............................. ±16 V to AGNDMaximum power-on voltage1 ................ ±110 mV

Output FIFO size.................................... 8,191 samples, shared among channels used

Texas Instruments Components in NI myDAQIntegrated circuits supplied by Texas Instruments form the power and analog I/O subsystems of NI

myDAQ. Figure 2 depicts the arrangement and function of the NI myDAQ subsystems. Table 5 lists all

of the Texas Instruments components used in NI myDAQ. Visit www.ti.com to see the specificationsdocuments for each of the components in the design.



Texas Instruments Components in NI myDAQ

NI myDAQ Hardware Block Diagram

Power SuppliesThere are three power supplies available for use on NI myDAQ. +15 V and – 15 V can be used

to power analog components such as operational amplifiers and linear regulators. +5 V can be used topower digital components such as logic devices The total power available for the power supplies

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