1 Introduction 2. Theory

CONTENTS 1 INTRODUCTION 2. THEORY 2.1 ELECTRIC MOTOR 2.1.1 DC MOTOR 2.1.2 NEED OF SPEED CONTROL 2.1.3 FACTORS CONTROLLING MOTOR SPEED

3. SPEED CONTROL OF SHUNT MOTORS 3.1 VARIATION OF FLUX OR FLUX CONTROL METHOD 3.2 ARMATURE OR RHEOSTATIC CONTROL METHOD 3.3 VOLTAGE CONTROL METHOD 3.3.1 MULTIPLE VOLTAGE CONTROL 3.3.2 WARD-LEONARD SYSTEM

3.4 MERITS AND DEMERITS OF RHEOSTATIC CONTROL METHOD 3.5 ADVANTAGES OF FIELD CONTROL METHOD 3.6 ELECTRONIC SPEED CONTROL METHODS FOR DC MOTORS

4. PULSE-WIDTH MODULATION 4.1 PRINCIPLE 4.2 CI RCUI T DESC RI PTI O N 4. 3 PO WER SUPPLY 4. 4 CO NSTR UCTI O N 4.5 APPLI C ATI O NS 4.6 ADVANTAGE OF PULSE WIDTH MODULATION 4.7 DISADVANTAGES OF PULSE WIDTH MODULATION

5 CONCLUSIONS

1|Page

LIST OF FIGURES

Figure No.

Description 1

flux or fields control method

2

Armature or Rheostatic Control Method

3

Ward-Leonard system

4

circuit diagram of the PMW

5

power supply

Page No

2|Page

Table No.

Description

1

RES 22K OHM 1/4W 5% CARBON FILM - CFR-25JB-22K – Resistors

2

RES 10K OHM 1/4W 5% CARBON FILM

3

RES 100k OHM 1/4W 5% CARBON FILM

4

RES 3k3 OHM 1/4W 5% CARBON FILM

5

RES 1k OHM 1/4W 5% CARBON FILM

6

RES 1M OHM 1/4W 5% CARBON FILM

7

1000 micro F/25V CAPACITOR

8

HEF40106BP IC SCHMITT TRIGGER HEX 14DIP

9

BC557 TRANS PNP Transistors (BJT)

10

2N3055 TRANS NPN Transistors (BJT) – Single

11

1N4007 Diodes, Rectifiers

12

1N4148 Diodes, Rectifiers

Page No

LIST OF TABLES

3|Page

DATA SHEET COMPONENT

DESCRIPTION

1N4148

Switching Diode

2N3055

Silicon NPN Power Transistor

BC557

PNP general purpose transistors

HEF40106B

Hex inverting Schmitt trigger

PAGE NO.

4|Page

1. INTRODUCTION: •

Almost all the machine in industries operated using electrical motors. Among them most of

motors are DC motors. As compare to the other motors DC motor is far more advantageous in terms of compactness, speed control facility, high starting torque. Among all the advantages the DC series motor is mostly used for its high starting torque & variable speed. DC series motor is specially used for traction, electric locomotive, trolley systems, cranes hoists and conveyor. All these works require frequent speed control for preparation of job.DC shunt motor is for constant speed operations. Therefore they are used for driving constant speed shafts, centrifugal pumps, blower & pumps etc. •

Traditional methods of speed control are basically controlling the voltage to the armature or to

the speed through rheostatic methods, controlling flux to the field through rheostatic method. •

But they are faulty and, not accurate & low efficient. Therefore they are discarded and adopted

electronic method of controlling the speed. They have more advantages like high reliability, quick response and also higher efficiency and no moving parts. But in PWM duty cycle control techniques enable greater efficiency and versatility of the brushless DC motor to provide flexible control and novel cyclic operation, as well as better protection schemes for the motor and control circuits. The high efficiency, higher power densities and reliability make brushless DC (BLDC) motors an ideal choice for battery-operated motor applications because the combination of power electronics and innovative control techniques provide a high performance, efficient, compact and low cost solution. A PWM (Pulse Width Modulation) wave can be used to control the speed of the motor. Here the average voltage given or the average current flowing through the motor will change depending on the ON and OFF time of the pulses controlling the speed of the motor i.e.. The duty cycle of the wave controls its speed.

5|Page

2.THEORY : 2.1 ELECTRIC MOTOR :

An electric motor uses electrical energy to produce mechanical energy, usually through the interaction of magnetic fields and current-carrying conductors. Electric motors may be classified by the source of electric power, by their internal construction, and by their application. The classic division of electric motors has been that of Alternating Current (AC) types vs Direct Current (DC) types. 2.1.1 DC MOTOR:

A DC motor is an electric motor that runs on direct current (DC) electricity. By far the most common DC motor types are the brushed and brushless types, which use internal and external commutation respectively to create an oscillating AC current from the DC source—so they are not purely DC machines in a strict sense. 2.1.2 NEED OF SPEED CONTROL:

The purpose of a motor speed controller is to take a signal representing the demanded speed, and to drive a motor at that speed. The controller may or may not actually measure the speed of the motor. If it does, it is called a Feedback Speed Controller or Closed Loop Speed Controller, if not it is called an Open Loop Speed Controller. Feedback speed control is better, but more complicated, and may not be required for a simple robot design. The speed of a DC motor is directly proportional to the supply voltage, so if we reduce the supply voltage from 12 Volts to 6 Volts, the motor will run at half the speed. How can this be achieved when the battery is fixed at 12 Volts. The speed controller works by varying the average voltage sent to the motor. It could do this by simply adjusting the voltage sent to the motor, but this is quite inefficient to do. A better way is to switch the motor's supply on and off very quickly. If the switching is fast enough, the motor doesn't notice it, it only notices the average effect. 2.1.3 Factors Controlling Motor Speed

It has been shown earlier that the speed of a motor is given by the relation

where , Ra = armature circuit resistance. It is obvious that the speed can be controlled by varying (i) flux/pole, Φ (Flux Control) (ii) resistance Ra of armature circuit (Rheostatic Control) and (iii) applied voltage V (Voltage Control). These methods as applied to shunt, compound and series motors will be discussed below.

6|Page

3. Speed Control of Shunt Motors 3.1 Variation of Flux or Flux Control Method It is seen from above that N ∝ 1/Φ . By decreasing the flux, the speed can be increased and vice versa. Hence, the name flux or fields control method. The flux of a d.c. motor can be changed by ch,mging Ish with the help of a shunt field rheostat. Since Ish is relatively V small, shunt field rheostat has to carry only a small current, which means I2R loss is small, so that rheostat is small in size. This method is, therefore, very efficient. In non-interpolar machines, the speed can be increased by this method in the ratio 2 : 1. Any further weakening of flux Φ adversely affects the commutation and hence puts a limit to the maximum speed obtainable with this method. In machines fitted with interpoles, a ratio of maximum to minimum speeds of 6 : 1 is fairly common.

FIG. 1

3.2 Armature or Rheostatic Control Method This method is used when speeds below the no-load speed are required. As the supply voltage is normally constant, the voltage across the armature is varied by inserting a variable rheostat or resistance (called controller resistance) in series with the armature circuit as shown in Fig. 25-3 (a). As controller resistance is increased, p.d. across the armature is decreased, thereby decreasing the armature speed. For a load of constant torque I speed is approximately- proportional to the p.d. across the armature. From the speed/armature current characteristic [Fig. 25-3 (b)], it is seen that greater the resistance in the armature circuit, greater is the fall in speed. Let Ia1 = armature current in the first case

7|Page

Ia2 = armature current in the second case (If Ia1 = Ia2, then the load is of constant torque) N1, N2 = corresponding speeds; V = supply voltage Then N1 ∝ V - Ia1Ra ∝ Eb1

Let some controller resistance of value R be added to the armature circuit resistance so that its value becomes (R+Ra) = Rt

FIG 2

The load current for which the speed would be zero is found by putting N = 0 in the above relation.

8|Page

This is the maximum current and is known as stalling current. As will be shown in Art. 25.4, this method is very wasteful, expensive and unsuitable for rapidly changing loads because for a given value of Rt, speed will change with load. A more stable operation can be obtained by using a divertor across the armature in addition to armature control resistance (Fig. 25.5) Now, the changes in armature current (due to changes in the load Fig. 25-5 torque) will not be so effective in changing the p.d. across the armature (and hence the armature speed).

FIG 3

3.3 Voltage Control Method 3.3.1 Multiple Voltage Control In this method, the shunt field of the motor is connected permanently to a fixed exciting voltage, but the armature is supplied with different voltages by connecting it across one of the several different voltages by means of suitable switchgear. The armature speed will be approximately proportional to these different voltages. The intermediate speeds can be obtained by adjusting the shunt field regulator. This method is not much used however. 3.3.2 Ward-Leonard System This system is used where an unusually wide (upto 10 : 1) and very sensitive speed control is required as for colliery winders, electric excavators, elevators and the main drives in steel mills and blooming and paper mills. The arrangement" is illustrated in Fig. 25-8. M1 is the main motor whose speed control is required. The field of this motor is permanently connected across the d.c. supply lines. By applying a variable voltage, across its armature, any desired speed can be obtained. 9|Page

This variable voltage is supplied by a motor-generator set which consists of either a d.c. or an a.c. motor M2 directly coupled to generator G. The motor M2 runs at an approximately constant speed. The output voltage of G is directly fed to the main motor M1 The voltage of the generator can be varied from zero up to its maximum value by means of its field regulator. By reversing the direction of the field current of G by means of the reversing switch RS, generated voltage can be reversed and hence the direction of rotation of M1, It should be remembered that motor generator set always runs in the same direction. Despite the fact that capital outlay involved in this system is high because (i) a large output machine must be used for the motor generator set and (ii) that two extra machines are employed, still it is used extensively for elevators, hoist control and for main drive in steel mills where motors of ratings 750 kW to 3750 kW are required. The reason for this is that the almost unlimited speed control in either direction of rotation can be achieved entirely by field control of the generator and the resultant economies in steel production outweigh the extra expenditure on the motor generator set.

FIG 4

A modification of the Ward-Leonard system is known as Ward-Leonard-lIgner system which uses a smaller motor-generator set with the addition of a flywheel whose function is to reduce fluctuations in the power demand from the supply circuit. When main motor M1 becomes suddenly overloaded the driving motor M2 of the motor generator set slows down, thus allowing the inertia of the flywheel to supply a. part of the overload. 10 | P a g e

However, when the load is suddenly thrown off the main motor M1, then M2 speeds up thereby again storing energy in the flywheel. When the Ilgner system is driven by means of an a.c. motor (whether induction or synchronous) another refinement in the form of a 'slip regulator' can be usefully employed thus giving an additional control. The chief disadvantage of this system is its low overall efficiency especially at light loads. But as said earlier, it has the outstanding merit of giving wide speed control from maximum in one direction through zero to the maximum in the opposite direction and of giving a smooth acceleration. 3.4 Merits and Demerits of Rheostatic Control Method 1. Speed changes with every change in load, because speed variations depend not only on controlling resistance but on load current also. This double dependence makes it impossible to keep the speed sensibly constant on rapidly changing loads. 2. A large amount of power is wasted in the controller resistance. Loss of power is directly proportional to the reduction in speed. Hence, efficiency is decreased. 3. Maximum power developed is diminished in the same ratio as speed. 4. It needs expensive arrangement for dissipation of heat produced in the controller resistance. 5. It gives speeds below the normal, not above it because armature voltage can be decreased (not increased) by the controller resistance. This method is, therefore, employed when low speeds are required for a short period only and that too occasionally as in printing machines and for cranes and hoists where motor is continually started and stopped. 3.5 Advantages of Field Control Method This method is economical, more efficient and convenient though it can give speeds above (not below) the normal speed. The only limitation of this method is that commutation becomes unsatisfactory, because the effect of armature reaction is greater on a weaker field. 3.6 Electronic Speed Control Methods for DC Motors  Of late, solid-state circuits using semi-conductor diodes and thyristors have become very popular for controlling the speed of a.c. and d.c. motors and are progressively replacing the traditional electric power control circuits based on thyratrons, ignitrons, mercury are rectifiers, magnetic amplifiers and

11 | P a g e

motor-generator sets etc. As compared to the electric and electromechanical systems of speed control, the electronic methods have higher accuracy, greater reliability, quick response and also higher efficiency, as there are no I2R losses and moving parts. Moreover, full 4-quadrant, speed control is possible to meet precise high speed standards.  All electronic circuits control the motor speed by adjusting either (i) the voltage applied to the motor armature or (ii) the field current or (iii) both.  DC motors can be run from the de supply if available or from ac supply after it has been converted into de supply with the help of rectifiers which can be either half-wave or full-wave and either controlled (by varying the conduction angle of the thyristors used) or uncontrolled.  AO motors can be run on the ac supply or form de supply after it has been converted into ac supply with the help of inverters (opposite of rectifiers).  As stated above, the average output voltage of a thyristor-controlled rectifier call be changed by changing its conduction angle and hence the armature voltage of the dc motor can be adjusted to control its speed. When run on a de supply, the armature de voltage can be changed with the help of a thyristor chopper circuit which can be made to interrupt de supply at different rates to give different average values of the de voltage. If de supply is not available it can be obtained from the available ac supply with the help of uncontrolled rectifiers (using only diodes and not thyristors). The de voltage so obtained can be then chopped with the help of a thyristor chopper circuit. A brief description of rectifiers, inverters and de choppers would now be given before discussing the motor speed control circuits. Conventional solutions for these applications use brushed DC motors (Figure 1). The speed control is achieved by reducing the voltage applied across the motor. Typical methods used are rheostat control or linear electronic control. While both methods provide a simple solution to the speed control of the DC motor, they suffer from several disadvantages that include: •

Low efficiency at low speeds and hence low charge cycle time for the battery

•

In linear electronic control circuit, the losses in the switch do not depend on the switch

characteristics. The switch must be large enough to dissipate the heat generated. This method is costly for high-power motor control applications. •

Speed can be controlled only below base speed 12 | P a g e

•

Speed control is possible in one direction only. Reversal of speed requires extra relays to switch

polarity of the voltage across the motor. •

Battery voltage variations can not be compensated

To overcome from the above problem a new technique is used which is known as pulse with modulation.

4. Pulse-width modulation:  Pulse-width modulation (PWM) is a very efficient way of providing intermediate amounts of electrical power between fully on and fully off. A simple power switch with a typical power source provides full power only, when switched on. PWM is a comparatively-recent technique, made practical by modern electronic power switches.  some variable-speed electric motors have had decent efficiency, but they were somewhat more complex than constant-speed motors, and sometimes required external electrical apparatus, such as a bank (group) of variable power resistorsThe term duty cycle describes the proportion of on time to the regular interval or period of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.PWM works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.PWM of a signal or power source involves the modulation of its duty cycle, to either convey information over a communications channel or control the amount of power sent to a load. 4.1 PRINCIPLE :The principle of controlling the DC power is simple by controlling the voltage or by current. But here the voltage and current is not controlled and also current is not controlled. But here the conduction time to the load is controlled. The main principle is control of power by varying by the varying the duty cycle .Simple we can take an example of the switch so that we can understand the principle. When a switch SW is closed for a time t1, the input voltage appears across the load. If the switch is off for t2 time the voltage across the load is zero.  The average voltage at output is given by V0 = 1/T

∫ vodt = t1/T Vs = ft1 Vs = kVs

 And the average load current , Ia = Va/R = KVs/R, where T is the chopping period, 13 | P a g e

k = t1/T is the duty cycle of chopper, and f is the chopping frequency.  The rms value of output voltage is found from V0 = ( i/T

∫

V02 dt ) ½ = k Vs

Assuming the loss less system,  the input power to the system is the same as the output power and is given by

Pi = 1/T

∫

v0idt

= 1/T

∫

v02/R

dt

=

kVs2/R

The duty cycle can be varied from 0 to 1 by varying t1, T1 or f. Therefore, the output voltage V0 can be varied from 0 to Vs by controlling k, and the power flow can be controlled. The frequency f is kept constant and the on-time t1 is varied. The width of the pulse is varied and this type of control is called pulse width modulation (PWM) control. 4.1 C I R C U I T D I A G R A M : -

Fig.5

14 | P a g e

4 .2 C I RC UI T DESC R I P TIO N :  This type of speed controller/governor is intended primarily for small 12v motors that draw a current of not more than 15A. Many governors limit the current through the motor, which also reduces the torque. Since it is controlled by pulse width modulation (PWM), the present governor preserves most of the torque.  The design is based on astable multivibrator IC1a, whose output is low for a period determined by R1 and high for a period set by R2 and P1. When C1 is discharged, the level at the input of IC1a is below the lower threshold, so that the output of this stage is high. The capacitor is then charged rapidly via D1 and R1, and reaches the upper threshold in about 1.5ms. the output of IC1a then goes low, whereupon C1 is discharged via D2, R2, and P1. The discharge time could be set between 0.2ms and 25ms. This means that the duty factor of the output signal may be varied between 5% and 90%.  The signal is inverted again and then applied to the input of transistor BC557 through 4k7. Which is basically acts as a buffer. It provides requisite drive signal to the power transistor. The transistor drives the motor. The diode connected across the motor is for freewheeling purpose. the resistance of P1 is at a minimum, the rotary speed of the motor is at a maximum. 4. 3 PO WER SUPPLY The microcontroller needed to be operate in DC power supply. The circuit & motor needs +12v supply. The transformer is a center tap 12-0-12V 500mA. It is then rectified using full wave rectifier. A 1000µ Fcapacitor is used for filtration purpose. The three terminal voltage regulators 7812 provides regulated DC outputs for the operation of the circuit. A good grounding is necessary for the proper functioning of the circuit.

15 | P a g e

FI G6

5. C O M P O N E N T T A B L E : SL 1

2

COMPONENT RESISTOR

CAPACITOR

3

SEMICONDUCTOR

4

TRANSFORMER

5

DC MOTOR 6

S C H M I T T T R I G G E R I NV E R T E R S

SPECIFICATION 22K

1

10K

1

4K7

1

100

1

3K3

1

1K

1

1M LIN 1000µ F/25V

1 1

100n 40106

1 1

BC557

1

2N3055

1

1N4007

2

1N4148

3

12-0-12/500Ma

1

12 VOLT

1

40106

QUANTITY

1

16 | P a g e

5.1 COMPNENT DESCRIPTION: RES 22K OHM 1/4W 5% CARBON FILM - CFR-25JB-22K – Resistors :

Technical/Catalog Information Vendor

CFR-25JB-22K Yageo

Category

Resistors

Resistance In Ohms

22.0K

Power (Watts)

0.25W, 1/4W

Tolerance

±5%

Lead Style

Through Hole

Case

Axial

Packaging

Bulk

Composition

Carbon Film

Temperature Coefficient

350ppm/°C

Lead Free Status

Lead Free

RoHS Status

RoHS Compliant

17 | P a g e

Other Names

CFR 25JB 22K CFR25JB22K 22KQBK ND 22KQBKND 22KQBK

18 | P a g e



 RES 10K OHM 1/4W 5% CARBON FILM :

Datasheets

CFR Carbon Film Resistor Series

Product Photos

CFR-25JB-10K

Product Training Modules Leaded Resistors Catalog Drawings

Carbon Film Resistor Derating Curve

Standard Package

200

Category

Resistors

Family

Through Hole Resistors

Series

CFR

Resistance In Ohms

10.0K

Composition

Carbon Film

Power (Watts)

0.25W, 1/4W

Temperature Coefficient

350ppm/°C

Case

Axial

Lead Style

Through Hole

Tolerance

±5%

Packaging

Bulk

Other Names

10K CR-1/4W-B 5% 10KQ 10KQBK CFR-25JB 10K

19 | P a g e

 RES 100k OHM 1/4W 5% CARBON FILM :

Digi-Key Part Number Manufacturer Part Number Description

MCF-25JR-100K-ND MCF-25JR-100K RES CARB FILM 100K OHM 1/4W 5%

Series Manufacturer Resistance In Ohms Composition Power (Watts) Temperature Coefficient

MCF Yageo 100K Carbon Film 0.25W, 1/4W 0/-600ppm/°C

Case

5.90mm L x 2.20mm Dia

Lead Style

Surface Mount (SMD - SMT)

Tolerance

±5%

Packaging

Tape & Reel (TR)

20 | P a g e

 RES 3k3 OHM 1/4W 5% CARBON FILM : Digi-Key Part Number

MCF-25JR-3K3-ND

Manufacturer Part Number

MCF-25JR-3K3

Description

RES CARB FILM 3.3K OHM 1/4W 5%

Series

MCF

Manufacturer

Yageo

Resistance In Ohms

3.30K

Composition

Carbon Film

Power (Watts)

0.25W, 1/4W

Temperature Coefficient

0/-350ppm/°C

Case

5.90mm L x 2.20mm Dia

Lead Style

Surface Mount (SMD - SMT)

Tolerance

±5%

Packaging

Tape & Reel (TR)

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 RES 1k OHM 1/4W 5% CARBON FILM :

Digi-Key Part Number

MCF-25JR-1K-ND

Manufacturer Part Number

MCF-25JR-1K

Description

RES CARB FILM 1K OHM 1/4W 5%

Series

MCF

Manufacturer

Yageo

Resistance In Ohms

1.00K

Composition

Carbon Film

Power (Watts)

0.25W, 1/4W

Temperature Coefficient

0/-350ppm/°C

Case

5.90mm L x 2.20mm Dia

Lead Style

Surface Mount (SMD - SMT)

Tolerance

±5%

Packaging

Tape & Reel (TR)

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 RES 1M OHM 1/4W 5% CARBON FILM :

Digi-Key Part Number

1.0MQBK-ND

Manufacturer Part Number

CFR-25JB-1M0

Description

RES 1.0M OHM 1/4W 5% CARBON FILM

Series

CFR

Manufacturer

Yageo

Resistance In Ohms

1.00M

Composition

Carbon Film

Power (Watts)

0.25W, 1/4W

Temperature Coefficient

-1500ppm/°C

Case

Axial

Lead Style

Through Hole

Tolerance

±5%

Packaging

Bulk

23 | P a g e

 1000 micro F/25V CAPACITOR : Digi-Key Part Number

P1225-ND

Manufacturer Part Number

ECE-A1EFS102

Description

1000UF/25V HFS CAPACITOR

Series

HFS

Manufacturer

Panasonic - ECG

Capacitance

1000µF

Voltage Rating

25V

Tolerance

±20%

Mounting Type

Through Hole

Package / Case

Radial

Size / Dimension Lead Spacing

0.630" Dia x 0.984" H (16.00mm x 25.00mm) 0.295" (7.50mm)

Maximum Temperatur

-40°C ~ 85°C

Features

General Purpose

Packaging

Bulk

24 | P a g e

 HEF40106BP IC SCHMITT TRIGGER HEX 14DIP : Digi-Key Part Number Manufacturer Manufacturer Part Number Description Lead Free Status / RoHS Status Category Family Series Logic Type Number of Inputs Number of Circuits Current - Output High, Low Voltage – Supply Operating Temperature Mounting Type

568-1681-5-ND NXP Semiconductors HEF40106BP,652 IC SCHMITT TRIGGER HEX 14DIP Lead free / RoHS Compliant Integrated Circuits (ICs) Logic Family - Gates and Inverters 4000B Inverter with Schmitt Trigger 1 6 - Hex 2.4mA, 2.4mA 4.5 V ~ 15.5 V -40°C ~ 125°C Through Hole

Package / Case

14-DIP (300 mil)

Packaging

Tube

Other Names

568-1681-5 HEF40106BPN

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 BC557 TRANS PNP Transistors (BJT) : Digi-Key Part Number Manufacturer Manufacturer Part Number Description Lead Free Status / RoHS Status Category Family Voltage - Collector Emitter Breakdown (Max) Vce Saturation (Max) @ Ib, Ic Current - Collector (Ic) (Max) Current - Collector Cutoff (Max) DC Current Gain (hFE) (Min) @ Ic, Vce Power - Max Frequency - Transition Transistor Type Mounting Type

BC557-ND Fairchild Semiconductor BC557 TRANS PNP 45V 100MA TO-92 Lead free / RoHS Compliant Discrete Semiconductor Products Transistors (BJT) - Single 45V 300mV @ 500µA, 10mA 100mA

Package / Case

TO-92-3 (Standard Body), TO-226

Packaging

Bulk

110 @ 2mA, 5V 500mW 150MHz PNP Through Hole

 2N3055 TRANS NPN Transistors (BJT) – Single : Digi-Key Part Number Manufacturer

2N3055GOS-ND ON Semiconductor

26 | P a g e

Manufacturer Part Number Description Lead Free Status / RoHS Status Category Family Voltage - Collector Emitter Breakdown (Max) Vce Saturation (Max) @ Ib, Ic Current - Collector (Ic) (Max) Current - Collector Cutoff (Max) DC Current Gain (hFE) (Min) @ Ic, Vce Power - Max Transistor Type Mounting Type Package / Case

2N3055G TRANS NPN 15A 60V TO3 Lead free / RoHS Compliant Discrete Semiconductor Products Transistors (BJT) - Single 60V 1.1V @ 400mA, 4A 15A 700µA 20 @ 4A, 4V 115W NPN Chassis Mount TO-204, TO-3

Packaging

Tray

 1N4007 Diodes, Rectifiers :

Digi-Key Part Number

1N4007FSCT-ND

Manufacturer

Fairchild Semiconductor

Manufacturer Part Number

1N4007

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Description

DIODE GPP 1A 1000V DO41

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

Product Training Modules

High Voltage Switches for Power Processing

Category

Discrete Semiconductor Products

Family

Diodes, Rectifiers - Single

Voltage - DC Reverse (Vr) (Max)

1000V (1kV)

Voltage - Forward (Vf) (Max) @ If

1.1V @ 1A

Current - Average Rectified (Io)

1A

Current - Reverse Leakage @ Vr

5µA @ 1000V

Diode Type

Standard

Speed

Standard Recovery >500ns, > 200mA (Io)

Capacitance @ Vr, F

15pF @ 4V, 1MHz

Mounting Type

Through Hole, Axial

Package / Case

DO-41, Axial

Packaging

Cut Tape (CT)

 1N4148 DIODES, RECTIFIERS :

The 1N4148 is a standard small signal silicon diode used in signal processing. Its name follows the JEDEC nomenclature. The 1N4148 is generally available in a DO-35 glass package and is very useful at high frequencies with a reverse recovery time of no more than 4ns. This permits rectification and detection of radio frequency signals very

28 | P a g e

effectively, as long as their amplitude is above the forward conduction threshold of silicon (around 0.7V) or the diode is biased. Digi-Key Part Number

1N4148FS-ND

Manufacturer

Fairchild Semiconductor

Manufacturer Part Number

1N4148

Description

DIODE SGL JUNC 100V 4.0NS DO-35

Lead Free Status / RoHS Status

Lead free / RoHS Compliant

Product Training Modules

High Voltage Switches for Power Processing

Product Change Notification

Marking Format Change 15/Aug/2008

Category

Discrete Semiconductor Products

Family

Diodes, Rectifiers - Single

Voltage - DC Reverse (Vr) (Max)

100V

Voltage - Forward (Vf) (Max) @ If

1V @ 10mA

Current - Average Rectified (Io)

200mA

Current - Reverse Leakage @ Vr

5µA @ 75V

Diode Type

Standard

Speed

Small Signal =< 200mA (Io), Any Speed

Reverse Recovery Time (trr)

4ns

Capacitance @ Vr, F

4pF @ 0V, 1MHz

Mounting Type

Through Hole, Axial

Package / Case

DO-35, DO-204AH, Axial

Packaging

Bulk

TRAN SFO RM ER –12- 0- 12/ 500M a : 12-0-12 means that the voltage or the potential difference (p.d.) between each of the end terminals of the secondary winding and the mid-point of the secondary winding of the transformer is 12V. And, between the two ends of the secondary winding, you will get 12 + 12 = 24V. 500mA means the current delivery capability of the secondary winding of the transformer. Normally it is said in VA. In your case it would be 25 x 0.5 =

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12VA. The ratings are arrived at based on the requirements of the loads that are to be connected to the transformer. The limiting criteria is the winding wire thickness and the insulation of the winding. SPECIFICATION: •

Dimensions 56 x 47 x 43 mm

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Power Input 220-240 ac @50HZ

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Type 500mA Secondary

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Outputs 0-12/0-12 Vac

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Power 12VA

4 . 4 CONSTRUCTION :The circuit board is divided into several parts like power supply, motor controller sections. So there are three PCBs used for the application. Before mounting the components on PCB, PCB is to be thoroughly checked using eyeglass, as there are no cracks on the board. All the components are to be 30 | P a g e

mounted on the PCB by soldering it. Therefore during soldering the soldering technique is to be followed so that any soldering should not be dry solder one. IC’s to be mounted on the IC bases for better servicing facility. The high power device (2N3055 TRANSISTOR) is mounted on a plate for cooling purpose. The output of transistor is fed to the small DC motor armature. We can use more power TRANSISTOR we can control big motors. Ac cord is to be connected to the transformer to supply 220 v A.C. Transformer used here is 12-0-12, center tapped one. 4.5 APPLI CATI O NS : Now a day’s various applications are done using motors. Most of them are DC motor for their greater advantages like compact, variable speed, instant speed rise, high starting torque etc. Among DC motors there is greater use of DC series motor for its greater starting torque & variable speed. It uses the PWM technique for it. It is used for smooth acceleration control, high efficiency, and fast dynamic response. DC motors require smooth control for certain type of applications. So the speed to the load is essentially controlled to obtain a variable load output so that jobs can be prepared. This type of speed control is necessary in traction DC motor trolley cars, marine hoists, forklift truck, and mine haulers. Also the present project can control up to 1 percent of full speed, therefore high accuracy jobs acne be done using the project. So we can recognize some areas of application of this type of power control:  Traction application  Conveyor Belt carrying loads  Various motors requiring smooth speed control  DC motors of all range can be controlled, which are used for the production of materials  Electric locomotives  DC motor using precise job preparations.

4.6 ADVANTAGE OF PULSE WIDTH MODULATION :

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•

PWM duty cycle control techniques enable greater efficiency and versatility of the brushless DC

motor to provide flexible control and novel cyclic operation, as well as better protection schemes for the motor and control circuits. The high efficiency, higher power densities and reliability make brushless DC (BLDC) motors an ideal choice for battery-operated motor applications because the combination of power electronics and innovative control techniques provide a high performance, efficient, compact and low cost solution. •

PWM switching control methods improve speed control and reduce the power losses in the

system, which increase the mean time between charge cycles of the battery. The reduced losses also help reduce the weight of the system as smaller thermal management components are needed. These two factors are critical for portable equipment. •

PWM control methods also enable novel control methods and leverage the latest silicon

advancements to reduce losses in the system. With appropriate circuit and control methods, speeds above base speed can be achieved. Moreover, rugged power switches and feature-rich gate drive ICs improve the ruggedness and reliability of the system •

The advantage of pulse width modulation is that the pulses reach the full supply voltage and will

produce more torque in a motor by being able to overcome the internal motor resistances more easily. Finally, in a PWM circuit, common small potentiometers may be used to control a wide variety of loads whereas large and expensive high power variable resistors are needed for resistive controllers.

4.7 DISADVANTAGES OF PULSE WIDTH MODULATION :  The main Disadvantages of PWM circuits are the added complexity and the possibility of

generating radio frequency interference (RFI). RFI may be minimized by locating the controller near the load, using short leads, and in some cases, using additional filtering on the power supply leads.  it can give speed below the full speed, not above.  It cannot be used for fast controlling of speed.

5 . CO NCLUSI O N : 32 | P a g e

The present project is practical one and high feasibility according to economic point of view, reliability & accuracy. It is programmable one therefore it can control various motors ranging small one to several HP motors. It cannot be used for fast controlling of speed, where quick speed changing is necessary. These problems can be eradicated by more research.

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