automatic speed controller f0r fans
TRANSCRIPT
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.
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1 . BLOCK DIAGRAM
1.1 BLOCK DIAGRAM REPRESENTATION
fig
Figure. 1 block diagram of automatic speed controller for fans
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Power supply
Astable Multivibrator
Counter
Fan
Speed
Regulator
Transistor-Relay arrangement
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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
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Transformer Rectifier Filter Regulator
AUTOMATIC SPEED CONTROLLER F0R FANS
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.
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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.
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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
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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
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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
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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.
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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
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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
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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
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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.
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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
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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.
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4.1.1 COMPONENT LAYOUT
Figure. 5 component layout
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4.1.2 PCB LAYOUT
Figure. 6 PCB layout
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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.
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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.
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BIBLIOGRAPHY
1. www.efy.com
2. www.discovercircuits.com
3. www.circuitslab.com
4. www.alldatasheets.com
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APPENDIX
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