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 CIRCUIT DESCRIPTION

4.3 POWER SUPPLY

4.4 CONSTRUCTION

4.5 APPLICATIONS

4.6 ADVANTAGE OF PULSE WIDTH MODULATION

4.7 DISADVANTAGES OF PULSE WIDTH MODULATION

5 CONCLUSIONS

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Figure No. Description Page No

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

LIST OF FIGURES

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Table No. Description Page No

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

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

LIST OF TABLES 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

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DATA SHEET

COMPONENT DESCRIPTION PAGE NO.

1N4148 Switching Diode

2N3055 Silicon NPN Power Transistor

BC557 PNP general purpose transistors

HEF40106B Hex inverting Schmitt trigger

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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.

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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 Control l ing 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, (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.

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

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

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

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

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

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

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

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

3. Speed Control of Shunt Motors

3.1 Variation of Flux or Flux Control Method

It is seen from above that N 1/. 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 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

Ia2 = armature current in the second case

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(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.

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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.

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.

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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.

However, when the load is suddenly thrown off the main motor M1, then M2 speeds up thereby again storing

energy in the flywheel.

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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

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

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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

• 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

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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,

k = t1/T is the duty cycle of chopper, and f is the chopping frequency.

The rms value of output voltage is found from

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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 CIRCUIT DIAGRAM : -

F ig .5

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4.2 CIRCUIT DESCRIPTION : -

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 POWER 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 1000Fcapacitor

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.

FI

G 6

15 | P a g e

5. COMPONENT TABLE:-

SL COMPONENT SPECIFICATION QUANTITY

1 RESISTOR 22K

10K

4K7

100

3K3

1K

1M LIN

1

1

1

1

1

1

1

2 CAPACITOR 1000F/25V

100n

1

1

3 SEMICONDUCTOR 40106

BC557

2N3055

1N4007

1N4148

1

1

1

2

3

4 TRANSFORMER 12-0-12/500Ma 1

5 DC MOTOR 12 VOLT 1

6 SCHMITT TRIGGER INVERTERS 40106 1

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5.1 COMPNENT DESCRIPTION:

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

Technical/Catalog Information CFR-25JB-22KVendor 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

Other Names CFR 25JB 22KCFR25JB22K22KQBK ND22KQBKND22KQBK

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javascript:location.href='http://www.digikey.com/scripts/Redirect/Redirect.dll?R=9&V=13'

javascript:location.href='http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=13&M=CFR-25JB-22K'

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 ResistorDerating Curve

Standard Package 200

Category Resistors

Family Through Hole Resistors

Series CFR




Temperature Coefficient 350ppm/°C

Case Axial


Tolerance ±5%

Packaging Bulk

Other Names 10K CR-1/4W-B 5%10KQ10KQBKCFR-25JB 10K

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

Digi-Key Part Number MCF-25JR-100K-ND

Manufacturer Part Number MCF-25JR-100K

Description RES CARB FILM 100K OHM 1/4W 5%

Series MCF

Manufacturer Yageo

Resistance In Ohms 100K



Temperature Coefficient 0/-600ppm/°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 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







Tolerance ±5%


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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







Tolerance ±5%


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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



Temperature Coefficient -1500ppm/°C

Case Axial


Tolerance ±5%

Packaging Bulk

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

Lead Spacing 0.295" (7.50mm)

Maximum Temperatur -40°C ~ 85°C

Features General Purpose

Packaging Bulk

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HEF40106BP IC SCHMITT TRIGGER HEX 14DIP :

Digi-Key Part Number 568-1681-5-ND

Manufacturer NXP Semiconductors

Manufacturer Part Number HEF40106BP,652

Description IC SCHMITT TRIGGER HEX 14DIP

Lead Free Status / RoHS Status Lead free / RoHS Compliant

Category Integrated Circuits (ICs)

Family Logic Family - Gates and Inverters

Series 4000B

Logic Type Inverter with Schmitt Trigger

Number of Inputs 1

Number of Circuits 6 - Hex

Current - Output High, Low 2.4mA, 2.4mA

Voltage – Supply 4.5 V ~ 15.5 V

Operating Temperature -40°C ~ 125°C


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 BC557-ND

Manufacturer Fairchild Semiconductor

Manufacturer Part Number BC557

Description TRANS PNP 45V 100MA TO-92


Category Discrete Semiconductor Products

Family Transistors (BJT) - Single

Voltage - Collector Emitter Breakdown (Max) 45V

Vce Saturation (Max) @ Ib, Ic 300mV @ 500µA, 10mA

Current - Collector (Ic) (Max) 100mA

Current - Collector Cutoff (Max)

DC Current Gain (hFE) (Min) @ Ic, Vce 110 @ 2mA, 5V

Power - Max 500mW

Frequency - Transition 150MHz

Transistor Type PNP


Package / Case TO-92-3 (Standard Body), TO-226

Packaging Bulk

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2N3055 TRANS NPN Transistors (BJT) – Single :

Digi-Key Part Number 2N3055GOS-ND

Manufacturer ON Semiconductor

Manufacturer Part Number 2N3055G

Description TRANS NPN 15A 60V TO3



Family Transistors (BJT) - Single

Voltage - Collector Emitter Breakdown (Max) 60V

Vce Saturation (Max) @ Ib, Ic 1.1V @ 400mA, 4A

Current - Collector (Ic) (Max) 15A

Current - Collector Cutoff (Max) 700µA

DC Current Gain (hFE) (Min) @ Ic, Vce 20 @ 4A, 4V

Power - Max 115W

Transistor Type NPN

Mounting Type Chassis Mount

Package / Case TO-204, TO-3

Packaging Tray

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1N4007 Diodes, Rectifiers :

Digi-Key Part Number 1N4007FSCT-ND


Manufacturer Part Number 1N4007

Description DIODE GPP 1A 1000V DO41


Product Training Modules High Voltage Switches for Power Processing


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)

27 | P a g e

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 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 Part Number 1N4148

Description DIODE SGL JUNC 100V 4.0NS DO-35


Product Training Modules High Voltage Switches for Power Processing

Product Change Notification Marking Format Change 15/Aug/2008


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

TRANSFORMER –12-0-12/500Ma :

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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 =

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

Power Input 220-240 ac @50HZ

Type 500mA Secondary

Outputs 0-12/0-12 Vac

Power 12VA

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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

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 APPLICATIONS :

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.

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4.6 ADVANTAGE OF PULSE WIDTH MODULATION :

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.

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5.CONCLUSION :

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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Documents

1 Introduction 2. Theory