automatic speed controller f0r fans

AUTOMATIC SPEED CONTROLLER F0R FANS

INTRODUCTION

During summer nights, the temperature is initially quite high. As time passes

the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of

one’s body decreases. Thus, initially the fan needs to be run at full speed. As time

passes, one has to get up again and again to adjust the speed of the fan. This interferes

with his/her sleeping period and thus he/she may not get sufficient rest leading to

mental strain.

The circuit presented here helps to overcome the above problem. Here the

fan runs at full speed for a predetermined time. The speed is decreased to medium

after some time, and to slow later on. After certain period the fan is switched off.

This circuit consists of IC1 (555), which is used as an astable – multivibrator to

generate clock pluses. The pulses are fed to decade divider/counter formed by IC2

(4017B) which is a 5-stage counter having 10 decoded output. The values of

capacitors and resistors of the multivibrator circuit are so adjusted that the final output

of IC2 goes high after the predetermined period. First the fan runs at high speed for a

particular period of time. Then the fan speed reduces to a medium .After some time to

a low value and then turns off. The speed control is achieved with the help of

transistor- relay arrangement. The transistor on/off is controlled with the help of the

diodes connected to the timer circuit. Whenever the transistor gets on it is connected

to the relay and the fan runs according to counter output.

Dept. of Electronics & Communication Engg. SJCET, Palai


1 . BLOCK DIAGRAM

1.1 BLOCK DIAGRAM REPRESENTATION

fig

Figure. 1 block diagram of automatic speed controller for fans


Power supply

Astable Multivibrator

Counter

Fan

Speed

Regulator

Transistor-Relay arrangement


1.2 BLOCK DIAGRAM EXPLANATION

POWER SUPPLY UNIT

ac dc o/p

Figure. 2 block diagram of power supply unit

The function of this unit is to provide sufficient power for the proper

functioning of the device. The power supply section provides a dc voltage of 6v.The

transformer is a step down transformer for low output voltage. The filter circuit

converts output of transformer to pulsating dc.The filter component smoothens output

and the regulator provides a regulated dc supply output.

ASTABLE MULTIVIBRATOR

IC NE555 is configured as astable unit. This unit produces a clock pulse. The

clock pulses are given to the counter circuit. The known values of capacitors and

resistors are placed in the shorted pins 6 and 7 of IC NE555 and ground. This circuit

does not require an external trigger to change the state of the output, hence the name

free-running. The time during which the output is either high or low is determined by

two resistors and capacitor, which are externally connected to the 555 timer.

COUNTER SECTION

This section receives the clock pulse from the astable unit. It uses a five stage

decade counter IC CD4017B having 10 decoded outputs. It acts as a ring counter. The


Transformer Rectifier Filter Regulator


counter output is connected to the regulator circuit through the transistor-relay

arrangement.

TRANSISTOR-RELAY ARRANGMENT

The fan speed is controlled by this section. Here this section determines the

speed levels by turning on and off the transistor –relay arrangement.

REGULATOR CIRCUIT

Regulator circuit is an electrical step one. In electrical regulator by using

resistance output voltage is varied simultateneouly the speed is varied. But to reduce

the energy loses in the resistor; electronic regulator is introduced, which uses triac to

vary the output voltage by varying the firing angle, which avoids lose of energy in

resistor.



2. CIRCUIT DESCRIPTION

2.1 POWERSUPPLY

Figure. 3 power supply unit

2.1.1 Description

The simple circuit of power supply is used here. A step down transformer is

used here for low output voltage .It provides the required magnitude of dc voltage.

The 230v is stepped down to 6v by the transformer

The transformer output is given to a rectifier circuit consisting of diodes

connected as a bridge. The bridge circuit rectifies ac input voltage to dc voltage. The

bridge network rectifies both half cycles of ac input voltage thus producing a

pulsating dc voltage.

Since pulsating dc voltage contains both dc as well as ac components, it is

necessary to remove the ac components. The filter circuit minimizes the ripples in the

rectified supply capacitor is used here.



The filtered output is given to regulator circuit. A regulator IC7806 is used

here. They do not require an external reference voltage. The device has three

terminals marked as input terminal, ground terminal, and output terminal.

2.2 CIRCUIT DIAGRAM

Figure. 4 circuit diagram



2.3 CIRCUIT EXPLANATION

Using the circuit we can control the speed of the fan automatically .Here IC1

(555) is used is an astable multivibrator to generate clock pulses. The pulses are fed to

decade dividers/counters formed by IC2. The IC2 act as ring counter. The values of

capacitor C1 and resistors R1 and R2 are so adjusted that the final output of IC2 goes

high after a predetermined time. The first two outputs of IC2 (Q0andQ1) are

connected via diodes D1 and D2 to the base of transistor T1. Initially output Q0 is

high and therefore relay RL1 is energized.

Initially the fan shall get AC supply directly, and so it shall run at top speed.

When output Q2 becomes high and Q1 becomes low, relay RL1 is turned off and

relay RL2 is switched on. The fan gets AC through a resistance and its speed drops to

medium. This continues until output Q4 is high. When Q4 goes low and Q5 goes

high, relay RL2 is switched off and relay RL3 is activated. The fan now runs at low

speed. Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping

T5 in saturation and RL4 on. At the end of the cycle, when pin 11 (Q9) becomes high,

T4 gets saturated and T5 is cut off. RL4 is switched off thus switching off the fan.

Using the circuit described above, the fan shall run at high speed for a

comparatively lesser time when either of Q0 or Q1 output is high. At medium speed,

it will run for a moderate time period when any of three outputs Q2 through Q4 is

high, while at low speed, it will run for a much longer time period when any of the

four outputs Q5 through Q8 is high. If one wishes, one can make the fan run at the

three speeds for an equal amount of time by connecting three decimal decoded

outputs of IC2 to each of the transistors T1 to T3. One can also get more than three



speeds by using an additional relay, transistor, and associated components, and

connecting one or more outputs of IC2 to it.

3. COMPONENETS AND SPECIFICATION

3.1 COMPONENTS LIST

NO ITEM SPECIFICATION QUANTITY

1 IC1 NE555 1

2 IC2 CD4017B 1

3 Resistor 47kΩ 1

4 Resistor 22kΩ 2

5 Resistor 10kΩ 4

6 Diode 1N4001 13

7 Capacitor 220µf 1

8 Capacitor 0.01µf 1

9 Transistor BC548 5

10 Relay 6v,100Ω,Spdt 4

11 Fan Regulator Step 1

12 Transformer Step down (0-12v) 1

13 Capacitor 0.01 µf 1

14 Capacitor 1000 µf 1

15 IC LM7806 1

16 Round bridge rectifier 1A 1

17 Led 1



4. PCB DESIGN AND FABRICATION

4.1 Printed Circuit Board

PCB is a platform where the electronic component can be inter connected

without wiring. PCBs make the electronic circuit manufacturing an easy one. In older

days vast area was required to implement a small circuit to connect the leads of the

components and separate connections were needed. But PCBs connect the two, by

copper coated lines on the PCB. In the single sided PCBs the copper layer is on one

side.

4.2 Board Types

The most popular board types are:

4.2.1 SINGLE-SIDED BOARDS: They mainly used in entertainment electronics

where manufacturing costs have to be kept the minimum.

4.2.2 DOUBLE-SIDED BOARDS: Double sided PCBs can be made with or without

plated through holes. The production of boards with plated through holes is fairly

expensive.

4.3 Manufacturing Process

First, the PCB layout of the required circuit is designed. The PCB layout is

then drawn on the plane copper coated board. These boards are available in two types.



1. Phenolic

2. Glass epoxy

Most computers, PCBs are glass epoxy. To draw the layout we can use black

color paints. Before that the required size of the plane PCB board is determined from

the roughly drawn PCB layout. Using black paint the desired layout is drawn on the

PCB.

4.4. Layout Approach

The first rule is to prepare each and every PCB layout as viewed from the

component side. Another important rule is to start the designing of a layout unless an

absolutely clear circuit diagram is available, if necessary, with a component list.

Among the components the larger ones are placed first and the space between

is filled with similar ones. Components requiring input/output connections come near

the connectors. All components are placed in such a manner that desoldering of other

components is not necessary if they have to be replaced.

In the designing of a PCB layout it is very important to divide the circuit into

functional subunits. Each of these subunits should be realized on a defined portion of

the board. In the designing in the inner connections which are usually done by pencil

lines, actual space requirements in the artwork must be considered. In addition the

layout can be rather roughly sketched and will still be clear enough for artwork

designer.

Board Cleaning

The cleaning of the copper surface prior to resist applications is an essential

step for any types of PCB process using etch or plating resist. Insufficient cleaning is

one of the reasons most often encountered for difficulties in PCB fabrication although

it might not always be immediately recognized as this. But it is quiet often the reasons



of poor-resist adhesion, uneven photo-resist films, pin holes, poor plating adhesion,

etc.

Where cleaning has to be done with simplest means or only for a limited

quantity of PCBs, manual-cleaning process is mainly used. In the process we require

just a sink with running water, pumice powder, scrubbing brushes and suitable tanks.

Screen Printing

This process is particularly suitable for large production schemes. However

the preparations of a screen can also be economically attractive for series of 1000

PCBs. Below, while photo printing is basically the non-accurate method to transfer a

pattern on to a board surface. With the screen-printing process one can produce PCBs

with a conduction width of as low as 0.5 + or – and a registration error of 0.1 mm on

an industrial scale with a high reliability.

In its basic form, the screen-printing process is very simple. A screen fabric

with uniform measures and opening is stretched and fixed on a solid frame of metal or

wood. The circuit pattern is photographically transferred on to the screen, leaving the

meshes in the pattern open, while the meshes in the rest of the area are closed. In the

actual printing process, ink is forced by the moving squeegee through the open

meshes on to the surface of the material to be printed.

Plating

From a practical stand port, PCBs may have to be stocked before being taken for

assembly of components. It is expected that the circuit board retain its solder ability

for long periods of several months so that reliable solder joints can be produced

during assembly. Plating of a metal can be accomplished on a copper pattern by three

methods. They are:

1. Immersion plating

2. Electro less plating



3. Electro plating

Etching

This can be done both by manual and mechanical ways by immersing the

board in to a solution of formic chloride and hydrochloric acid and finally cleaning

the board by soap. In all subtractive PCB processes, etching is one of the most

important steps. The copper pattern is formed by selective removal of all unwanted

copper, which is not protected by an etch resist. This look very simple at first glance

but in practice there are factors like under etching and overhang, which complicate the

matter especially in the production of fine and highly precise PCBs. Etching of PCBs,

as required in modern electronic equipment production, is usually done in spray type

etching machines.

Component Placing

The actual location of the components in the layout is responsible for the

problems to be placed during routing of inter connections .In a highly sensitive circuit

the critical components are placed first and in such a manner as to require minimum

length for the critical conductors. In less critical circuit the components are arranged

exactly in the order of signal flow. This will result in a minimum over all conductor

length. In a circuit where a few components have considerably more connecting

points than the others, these key components have to be placed first and the remaining

ones are grouped around.

The general result to be aimed at is always to get shortest possible inter

connections. The bending of the axial component leads is done in manner to guarantee

and optimum retention of the PCB while a minimum of stress is introduced on the

solder joint. The lead bending radius should be approximately two times the lead

diameter. Horizontally mounted resistors must touch the board surface to avoid lifting

of solder joints along with the copper pattern under pressure on the resistor body.

Vertically mounted resistors should not be flush to the board surface to avoid strain on



the solder joints as well as on the component lead junction due to different thermal

expansion coefficients of lead and board materials, where necessary resilient spaces

have to be provided. Coated or sealed components should have to be mounted in such

a way as to provide a certain length along the leads. Especially with plated through

holes where the solder flows up in the hole, clean leads of at least 1mm above the

board are recommended.

Drilling

Drilling of component mounting holes in to PCBs is by far the most important

mechanical machining operation in PCB production processes. Holes are made by

drilling where ever a superior hole finish for plated-through hole processes is require

and where the tooling costs for a punching tool cannot be justified.

There for drilling is applied by all the professional grade PCB manufactures

and generally in smaller PCB production laboratories.

The importance of drilling holes in to PCB has further gone up with electronic

component miniaturization and it needs smaller hole diameters and higher package

density where hole punching is practically ruled out.

Soldering

Soldering is a process for the joining of metal parts with the aid of a molten

metal (solder), where the molten temperature is suited below that of a material joint,

where by the surface of the parts are wetted, without then becoming molten.

Soldering generally implies that the joining process occurs at temperatures

below 450-degree centigrade’s. Solder wets and alloys with the base metal and gets

drawn, by capillary action, into the gap between them. This process forms a

metallurgical bond between the parts of the joint.

Therefore solder acts by:

Wetting of base metal surfaces forming joint.



Flowing between these surfaces, which result in completely filled space

between them.

Metallurgical bonding to these surfaces when soldered.

Soldering consists of the relative positioning of the surfaces to be joined,

wetting these surfaces with molten solder and allowing the solder to cool down until it

has solidified. During the soldering operations, an auxiliary medium is mostly used to

increase the flow properties of molten solder or to improve the degree of material.

Such a medium is called flux. Following characteristics are required in a flux:

It should provide a liquid cover over a material and exclusive air up to the

soldering temperature.

It should dissolve any oxide on the metal surface on the solder and carries

such unwanted elements away.

It should be readily displaced from the metal by the molten soldering

operation.

Residue should be removable after completion of the solder.

To achieve a soldered joint the solder and the base metal must be heated

above the melting point of the solder used. The metal by which the necessary

heat is applied, among other things depend on:

Nature and type of the joints

Melting point of the solder

Flux

Generally applied soldering methods are iron soldering, torch

soldering, mass soldering, and electrical soldering furnace soldering and

other methods. Components are basically mounted only one side of the board.

In double-sided PCBs, the components side is usually opposite to the major

conductor pattern side, unless otherwise dictated by special design

requirements.

The performance and reliability of solder joints give best results if lead

cutting is carried out before soldering so that the lead ends get protected and

also covered with solder and here with contributing to the actual solder



connections. However, lead cutting after soldering is still common in

particular in smaller industries where hand soldering is used.

With the soldered PCB many contaminance can be found which may

produce difficulties with the functioning of the circuit. The problems usually

arise at a much later than during the final functioning testing of the board in

the factory. Among the contaminants, we can typically find flux, chips of

plastics, metals and other constructional materials, plating sails, oils, greases,

environmental soil and other processing material.

The following performances are expected from the cleaning procedure with

the appropriate cleaning medium:

Dissolution or dissolving of organic liquids and solids, e.g., oils, greases, resin

fluxes.

Removal of plating salt and silicon oils.

Displacing of particulate and other insoluble matters, e.g., chips, dust, lint.

No severe attacks on boards and components to be cleaned, no alteration of ink

or paint notations and last but not the least, compatibility with healthy

environmental working conditions.

4.4.2 Proteus in PCB

First the PCB layout is designed by PROTEUS. The print out is taken

from the computer (of large size) for out clearance. This layer is given to the

photography section to get the layout.

This photographic image is exposed in the following three methods.

1. Polybluem

2. Chrombium

3. Five star

The exposed mesh is placed on the plain copper coated board in correct

alignment by using wooden clamps paint flow through the board and the

layout lines are made on the copper boards.



4.1.1 COMPONENT LAYOUT

Figure. 5 component layout



4.1.2 PCB LAYOUT

Figure. 6 PCB layout



5. RESULT ANALYSIS

5.1 RESULT

The “AUTOMATIC SPEED CONTROLLER FOR FANS” was designed and

implemented successfully. The working conditions and various constrains was

properly studied before carrying out further steps.

The PCB was fabricated as per requirements taking proper care to avoid

shortage between various connections. The output was verified on PCB also. We were

able to design the circuitry and could demonstrate it. An appropriate casing was made

for the device which was designed so as to make it a marketable product.



5.2 CONCLUSION AND FUTURE SCOPE

In our project, AUTOMATIC SPEED CONTROLLER FOR FANS was

designed and setup the project helped us to improve and made us familiarize with a

number of ic’s even though the circuitry is not much complex so it can be used by the

beginners to study about the circuit and its applications.

The circuit has limitation since it is preset it cannot sense the variations in the

environment and regulate the fan speed automatically.

Modifications can be done on the circuitry to make it more advanced. By

adding a temperature sensor we can sense the variation in the temperature and thereby

regulate the speed of the fan.



BIBLIOGRAPHY

1. www.efy.com

2. www.discovercircuits.com

3. www.circuitslab.com

4. www.alldatasheets.com


http://www.alldatasheets.com/


APPENDIX
