Automatic Fan Speed Controller without micro controller OR An intelligent speed governor for fan

An Intelligent Speed Governor For Fan

Mini Project Report 2015

CHAPTER 1 INTRODUCTION This is a device to control the speed of fan and coolers automatically. The device presented here makes the fan run at a full speed for pre determined time. This speed is decreased to medium after some time and to slow then onwards after a period of 8 hours, the fan or cooler is switched off. The circuit consist of IC1 (555 Timer IC) which is used as an astable multi vibrator used to generate clock pulses. These are fed to decade dividers or counters formed by IC2 and IC3 (IC CD4017B). These ICs act as divide by 10 and divide by 9 counters respectively. The values of capacitor C1 and resister R1 and R2 are adjusted so that the final output of IC3 goes high after 8 Hours. So during summer nights the temperature is quality high but as time passes temperature starts dropping. So it is required to reduce the speed of a fan or cooler after particular periods. By using this device these reducing can be done automatically. This also makes the reduced conception of power.

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CHAPTER 2 EXISTING SYSTEM In existing system the speed of the fans was changed manually using selector switch. By changing the position of selector switch the speed of fan increases / decreases. So the existing system has manually controlled speed regulator. This system is very difficult for us to vary the speed of the regulator manually during the sleeping time. So most of the times the speed of the fan will be in the same stage during night times.

Fig.2.1 Existing arrangement for fan speed control

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CHAPTER 3 PROPOSED SYSTEM

The existing system insists physical burden to users. In this proposed system we just made some changes or alternation to the existing system. In this proposed system, the manual operation was changed to automatic and thus it makes the user more userfriendly and helpful.

Fig.3.1 Modified arrangement for speed control

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CHAPTER 4 SYSTEM MODEL The system consists of an astable timer NE555, Decade counters CD4017B, Transistor BC 548, Relay and a Fan. 4.1 BLOCK DIAGRAM

Fig.4.1.Block Diagram 4.2 BLOCK DESCRIPTION 4.2.1 Power Supply A 6 to 9 v DC Power supply is used. It provides constant power supply to timer and other components respectively. 4.2.2 Astable Multivibrator It is used as a pulse generator circuit it’s high and low state are both unstable. It provides clock pulses for the working of the decade counter1. The output of the multivibrator toggles with the low and high continuously, infect generating a train of pulses.

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4.2.3 Decade Counter 1 It accepts the output from the astable multivibrator as clock pulse. And the counter starts counting when there is an output at the astable output. 4.2.4 Decade Counter 2 It accept the output from the decade counter1 and counter start counting till there is an output from the decade counter1 and it act as a divide by 9 counter. 4.2.5 Relay This device simply acts as an electronic switch. When the output from the decade counter 2 reaches the relay terminal it will control the speed of the fan or cooler by switching of relays.

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CHAPTER 5 HARDWARE DESCRIPTION 5.1 CIRCUIT DIAGRAM The figure below shows the circuit diagram of An Intelligent Speed Governor for Fan.

Fig 5.1. Circuit Diagram 5.2 CIRCUIT DIAGRAM DESCRIPTION In the circuit diagram IC1 (555 timer IC) act as an astable multivibrator. It is used to generate clock pulses. The pulses are fed to a decade divider counter, which is formed by IC2 and IC3. These ICs act as divide by 10 counters and divide by 9 counter respectively. The values of capacitors C1, resister R2 and R2 are so adjusted that the final output of IC3 goes high about 8hours. The first two outputs of IC3 (Q0 and Q1) are connected (0 Red) via diode D1 and D2 to the base of the transistor T1. Initially output Q0 is high and there for relay RL1 is energized. It remains energized when Q1 becomes high. The method of connecting the gadget of the fan or cooler is given in the figure 5.1.

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Initially the fan shall get A/C supply directly so it shall be run at high speed. When the output Q2 becomes high and Q1 becomes low, relay RL1 is turned off and relay RL2 is turned on. The fan gets A/C 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 activated thus the fan run at low speed. Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping T5 in saturation and relay RL4 is on. At the end of the cycle, when pin 11(Q9) becomes high T4 get saturated and T5 is cut off. Relay RL4 is switched off, thus switching of the fan or cooler. Using the given circuit 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 to Q4) is high, while at low speed it will run for a much longer time period when any of the four outputs(Q5 to Q8) is high. It is possible to make the fan run at the three speeds for an equal amount of time by connecting three terminal decoded outputs of IC3 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 IC3 to it. 5.3 DETAILED COMPONENTS DESCRIPTION 5.3.1 Power Supply The ac voltage, typically 220V rms, is connected to a transformer, which steps that ac voltage down to the level of the desired dc output. A diode rectifier then provides a full wave rectified voltage that is initially filtered by a simple capacitor filter to produce a dc voltage. A regulator circuit removes the ripples and also remains the same dc value even if the input dc voltage varies, or the load connected to the output dc voltage changes. This voltage regulation is usually obtained using one of the popular voltage regulator ic units. TRANSFORMER

RECTIFIER

FILTER

Fig.5.2. Block Diagram of Power supply

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LOAD

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Fig.5.3. Circuit Diagram of Power Supply Transformer Transformer is a device used to increment or decrement the input voltage given as per the requirement. The transformers are classified into two depending upon their functionality step down transformer and step up transformer. Here a step down transformer is used for stepping down the house hold ac power supply i.e. the 230240V power supply to 6V. Bridge Rectifier When four diodes are connected as shown in fig.5.3, the circuit is called as bridge rectifier. The input to the circuit is applied to the diagonally opposite corners of the network, and the output is taken from the remaining two corners. Let us assume that the transformer is working properly and there is a positive potential, at point A and a negative potential at point B. The positive potential at point A will forward bias D14 and reverse bias D17. The negative potential at point B will forward bias D15 and reverse D16. At this time D17 and D15 are forward biased and will allow current flow to pass through them, D14 and D16 are reverse biased and will block current flow. The path for current flow is from point B through D15, up through RL, through D17, through the secondary of the transformer back to point B. This path is indicated by the solid arrows.

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One half cycles later the polarity across the secondary of the transformer reverse, forward biasing D16 and D14 and reverse biasing D15 and D17. Current flow will now be from point A through D14, up through RL, through D16, through the secondary of T1, and back to point A. This path is indicated by the broken arrows. The current flow through RL is always in the same direction. Since current flows through the load (RL) during both half cycles of the applied voltage, this bridge rectifier is a full-wave rectifier. One advantage of a bridge rectifier over a conventional full-wave rectifier is that with a given transformer the bridge rectifier produces a voltage output that is nearly twice that of the conventional full-wave circuit. This may be shown by assigning values to some of the components shown in fig.6.4 and 6.5. Assume that the same transformer is used in both circuits. The peak voltage developed between points X and Y is 1000 volts in both circuits. In the conventional full-wave circuit is shown in Fig. 6.4, the peak voltage from the center tap to either X and Y is 500 volts. Since only one diode can conduct at any instant, the maximum voltage that can be rectified at any instant is 500 volts. The maximum voltage that appears across the load resistor is nearly but never exceeds 500 volts, as result of the small voltage drop across the diode. In the bridge rectifier shown in Fig.6.5, the maximum voltage that can be rectified is the full secondary voltage, which is 1000 volts. Therefore, the peak output voltage across the load resistor is nearly 1000 volts. With both circuits using the same transformer, the bridge rectifier circuit. IC Voltage Regulators Voltage regulators comprise class of widely used ICs. Regulator IC units contain the circuitry for reference source, comparator amplifier, control device, and overload protection all in a single IC. IC units provide regulation of either a fixed positive voltage, a fixed negative voltage, or an adjustably set voltage. The regulators can be selected for operation with load currents from hundreds of milli amperes to tens of amperes, corresponding to power ratings from milli watts to tens of watts.

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Fig.5.4. +6V Voltage Regulator A fixed three terminal voltage regulator has an unregulated dc input voltage, Vi, applied to one input terminal, a regulated dc output voltage, V0, from a second terminal, with the third terminal connected to ground. 5.3.2 IC CD 4017 Decade Counter The M74HC 4017 is a high speed CMOS decade counter divider fabricated with silicon gate C2 MOS Technology. The M74HC 4017 is a five stage Johnson counter with 10 decoded outputs. Each of the decoded outputs is normally low and sequentially goes high on the low to high transition of the clocked input. Each output stays high for 1 clock period of the low to high after output 10 goes slow, and can be used in conjunction with the clock enable (CKEN) to cascade several stages. The clock enabled input disables counting when in the high stage. A clear (CLR) input is also provide which when taken high sets all the decoded outputs low. All inputs are equipped with protection circuit against static discharge and transient excess voltage.

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IC CD 4017 Pin Connection

Fig.5.6 CD 4017 Pin Connection It has 16 pins and the functionality of each pin is explained as follows:  Pin-1: It is the output 5. It goes high when the counter reads 5 counts.  Pin-2: It is the output 1. It goes high when the counter reads 0 counts.  Pin-3: It is the output 0. It goes high when the counter reads 0 counts.  Pin-4: It is the output 2. It goes high when the counter reads 2 counts.  Pin-5: It is the output 6. It goes high when the counter reads 6 counts.  Pin-6: It is the output 7. It goes high when the counter reads 7 counts.  Pin-7: It is the output 3. It goes high when the counter reads 3 counts.  Pin-8: It is the Ground pin which should be connected to a LOW voltage (0V).  Pin-9: It is the output 8. It goes high when the counter reads 8 counts.  Pin-10:It is the output 4. It goes high when the counter reads 4 counts.  Pin-11:It is the output 9. It goes high when the counter reads 9 counts.

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 Pin-12:This is divided by 10 output which is used to cascade the IC with another counter so as to enable counting greater than the range supported by a single IC 4017.  Pin-13:This pin is the disable pin. In normal mode of operation, this is connected to ground or logic LOW voltage. If this pin is connected to logic HIGH voltage, then the circuit will stop receiving pulses and so it will not advance the count irrespective of number of pulses received from the clock.  Pin-14: This pin is the clock input. This is the pin from where we need to give the input clock pulses to the IC in order to advance the count. The count advances on the rising edge of the clock.  Pin-15: This is the reset pin which should be kept LOW for normal operation. If you need to reset the IC, then you can connect this pin to HIGH voltage.  Pin-16: This is the power supply (Vcc) pin. This should be given a HIGH voltage of 3V to 15V for the IC to function. IC CD 4017 Features    

Wide supply voltage range: 3V to 15V High noise immunity: 0.45V Medium speed operation: 5 MHz Low power: 10Micro W

 Fully static operation 5.3.3 IC NE555 Timer The IC was designed in 1971 by Hans R. Camenzind It has been hypothesized that the 555 got its name from the three 5kΩ resistors used within, Introduced in 1971 by Signetics, The 555 timer is an extremely versatile integrated circuit which can be used to build lots of different circuit. The simplicity of the timer in conjunction with its ability to produce long time delays in a verity of applications, has curved many designers from mechanical timers, op amp, and various discrete circuits into the ever increasing ranks of timer users. The 555 timer IC is an integrated circuit (chip) used in

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a variety of timer, pulse generation and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package. the 555 is still in widespread use, thanks to its ease of use, low price and good stability, and is now made by many companies in the original bipolar and also in low-power CMOS types.

IC NE555 Pin Connection

Fig.5.7 NE555 Pin Connection The connection of the pins for a DIP package is as follows:  Pin 1: Grounded Terminal: All the voltages are measured with respect to the Ground terminal.  Pin 2: Trigger Terminal: The trigger pin is used to feed the trigger input hen the 555 IC is set up as a monostable multivibrator. This pin is an inverting input of a comparator and is responsible for the transition of flip-flop from set to reset. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin.  Pin 3: Output Terminal: Output of the timer is available at this pin. There are two ways in which a load can be connected to the output terminal. One way is to connect between output pin (pin 3) and ground pin (pin 1) or between pin 3

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and supply pin (pin 8). The load connected between output and ground supply pin is called the normally on load and that connected between output and ground pin is called the normally off load.  Pin 4: Reset Terminal: Whenever the timer IC is to be reset or disabled, a negative pulse is applied to pin 4, and thus is named as reset terminal. The output is reset irrespective of the input condition. When this pin is not to be used for reset purpose, it should be connected to + VCC to avoid any possibility of false triggering.  Pin 5: Control Voltage Terminal: The threshold and trigger levels are controlled using this pin. The pulse width of the output waveform is determined by connecting a POT or bringing in an external voltage to this pin. The external voltage applied to this pin can also be used to modulate the output waveform. Thus, the amount of voltage applied in this terminal will decide when the comparator is to be switched, and thus changes the pulse width of the output. When this pin is not used, it should be bypassed to ground through a 0.01 micro Farad to avoid any noise problem.  Pin 6: Threshold Terminal: This is the non-inverting input terminal of comparator 1, which compares the voltage applied to the terminal with a reference voltage of 2/3 VCC. The amplitude of voltage applied to this terminal is responsible for the set state of flip-flop. When the voltage applied in this terminal is greater than 2/3Vcc, the upper comparator switches to +Vsat and the output gets reset.  Pin 7 : Discharge Terminal: This pin is connected internally to the collector of transistor and mostly a capacitor is connected between this terminal and ground. It is called discharge terminal because when transistor saturates, capacitor discharges through the transistor. When the transistor is cut-off, the capacitor charges at a rate determined by the external resistor and capacitor.  Pin 8: Supply Terminal: A supply voltage of + 5 V to + 18 V is applied to this terminal with respect to ground (pin 1). IC NE555 Features  Turn off less than 2 micro second

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 Operate in both astable and mono stable modes  High output current  Adjustable duty cycle  Temperature stability of .005 % per0C

Timer Functional Block Diagram

Fig.5.8 Functional Block Diagram of NE555

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The 555 timer consist of two voltage comparators, a by stable flip flop , a discharge transistor, and a resister divider network. The resistive divider network is used to set the comparator levels. Since all 3 registers are of equal value, the threshold comparator is referenced internally at 2/3 of supply voltage level and trigger comparator is referenced at 1/3 of supply voltage. The outputs of comparators are tied to the bi stable flip flop. When the trigger voltage is mode below 1/3 of the supply, the comparator changes state and sets the flip flop driving the output to the high state. The threshold pin normally monitors the capacitor voltage of the RC timing network. When the capacitor voltage exceeds 2/3 of the supply the threshold comparator resets the flip flop which in turn drives the output to a low state. When the output is in allow state, the discharged transistor is on there by discharging the external timing capacitor. Once the capacitor is discharges, the timer will await another trigger pulse, the timing cycle have been completed. 555 timer integrated timer is used for generating accurate time delays or oscillation. This will provide time delay ranging from micro seconds to hours. Maximum operating frequency is in excess of 500KHz. Outputs is TTL compactly. The 555 timer can b used with supply voltage in range +5V to +18V and can drive load up to 200mA 5.3.4 BC548 Transistor The BC548 is a general purpose NPN bipolar junction transistor. The BC548 is the modern plastic packaged BC108, and can be used in any circuit designed for the BC108 or BC148, The BC546 and BC547 are essentially the same as the BC548 but selected with higher breakdown voltages while the BC549 is low noise version, and the BC550 both high-voltage and low-noise. The BC556 to BC560 are the PNP counterparts of the BC546 to BC550, respectively.

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Fig.5.9. BC548 Transistor


Fig.5.10. BC548 Transistor Symbol

5.3.5 Relay Relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts. The coil current can be on or off so relays have two switch positions and they are double throw (change over) switches. Relays allow one circuit to switch a second circuit which can be completely separate from the first one. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits; the link is magnetic and mechanical.

Fig.5.11. 6V DC Relay The coil of a relay passes a relatively large current, typically 30mA for a 12V relay, but it can be as much as 100mA for relays designed to operate from lower voltages. Most ICs (chips) cannot provide this current and a transistor is usually used to amplify the small IC current to larger value required for the relay coil.

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Relays are usually SPDT or DPDT but they can have many more sets of switch contacts, for example relays with 4 sets of change over contacts are readily available. Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay.

Fig.5.12.Relay Switch The picture shows a working relay with its coil and switch contacts. You can see a lever on the left being attracted by magnetism when the coil is switched on. This lever moves the switch contacts. There is one set of contacts (SPDT) in the foreground and another behind them, making the relay DPDT The relay’s switch connections are usually labeled COM, NC and NO. COM

is

Common,

always

connect to this; it is the moving part of the switch.

5.3.6 Fan

Fig.5.13. Fan

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A ceiling fan is a mechanical fan, usually electrically powered, suspended from the ceiling of a room that uses hub-mounted rotating paddles to circulate air. A ceiling fan rotates much more slowly than an electric desk fan; it cools people effectively by introducing slow movement into the otherwise still, hot air of a room, inducing evaporative cooling. Fans never actually cool air, unlike air-conditioning equipment,

but

use

significantly

less

power

(cooling

air

is thermo

dynamically expensive). Conversely, a ceiling fan can also be used to reduce the stratification of warm air in a room by forcing it down to affect both occupants' sensations and thermostat readings, thereby improving climate control energy efficiency.

CHAPTER 6 IMPLEMENTATION AND DEBUGGING 6.1 HARDWARE DEVELOPMENT The system is designed with the help of digital and discrete components. The components used in the system are Digital ICs, Transistors, Relay circuit, Fan. 6.1.1 PCB Designing

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A Printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a nonconductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly or PCB Assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially produced electronic devices. Alternatives to PCBs include wire wrap and point-to-point construction. PCBs are often less expensive and more reliable than these alternatives, though they require more layout effort and higher initial cost. PCBs are much cheaper and faster for highvolume production since production and soldering of PCBs can be done by automated equipment. Much of the electronics industry’s PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization. Pattering (etching) The vast majority of printed circuit boards are made by bonding a layer of copper over the entire substrate, sometimes on both sides, (creating a “blank PCB”) then removing unwanted copper after applying a temporary mask (e.g., by etching), leaving only the desired copper traces. A few PCBs are made by adding traces to the bare substrate (or a substrate with a very thin layer of copper) usually by a complex process of multiple electroplating steeps. The PCB manufacturing method primarily depends on whether it is for production volume or sample/prototype quantities. Double sided boards or multi layer boards use plated through holes, called vias, to connect traces on either side of the substrate. Chemical etching Chemical etching is done with ferric chloride, ammonium per sulfate, or sometimes hydrochloric acid. For PTH (plated through holes), additional steps of electrolysis deposition are done after the holes are drilled, then copper is electroplated to build up the thickness, the boards are screened, and plated with Tin/Lead. The Tin/Lead becomes the resist leaving the bare copper to be etched away.

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The simplest method, used for small scale production and often by hobbyists is immersion etching, in which the board is submerged in etching solution such as ferric chloride. Compared with methods used for mass production, the etching time is long. Heat and agitation can be applied to the bath to speed the etching rate. In bubble etching, air is passed through the etchant bath to agitate the solution and speed up etching. Splash etching uses a motor driven puddle to splash boards with etchant; the process has become commercially obsolete since it is not as fast as spray etching. In spray etching, the etchant solution is distributed over the boards by nozzles, and recirculated by pumps. Adjustments of the nozzle pattern, flow rate, temperature, and etchant composition gives predictable control of etching rates and high production rates. As more copper is consumed from the boards, the etchant becomes saturated and less effective, different etchants have different capacities for copper, with some as high as 150 grams of copper per liter of solution. In commercial use, etchants can be regenerated to restore their activity, and the dissolved copper recovered and sold. Small scale etching requires attention to disposal of used etchant, which is corrosive and toxic due to its metal content. The etchant removes copper on all surfaces exposed by the resist. “Undercut” occurs when etchant attacks the thin edge of copper under the resist; this can reduce conductor widths and cause open circuits. Careful control of etch time is required to prevent undercut. Where metallic plating is used as a resist, it can “overhang” which can cause short circuits between adjacent traces when closely spaced. Overhang can be removed by wire brushing the board after etching.

Lamination Some PCBs have trace layers inside the CB and ate called multi layer PCBs. These are formed by bonding together separately etched thin boards. Drilling Holes through a PCB are typically drilled with small diameter drill bits made of solid coated tungsten carbide. Coated tungsten carbide is recommended since many board materials are very abrasive and drilling must be high RPM and high feed to be

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cost effective. Drill bits must also remain sharp so as not to mar or tear the traces. Drilling with high speed steel is simply not feasible since the drill bits will dull quickly and thus tear the copper and ruin the boards. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer generated files are also called numerically controlled drill (NCD) files or “Excellon files”. The drill file describes the location and size of each drilled holes. These holes are often filled with annular rings (hollow rivets) to create vias. Vias allow the electrical and thermal connection of conductors on opposite sides of the PCB. When very small vias are required, drilling with mechanical bits is costly because of high rates of wear and breakage. In this case, the vias may be evaporated by lasers. Laser drilled vias typically have an inferior surface finish inside the hole. These holes are called micro vias. It is also possible with controlled depth drilling, laser drilling, or by predrilling the individual sheets of the PCB before lamination, to produce holes that connect only some of the copper layers, rather than passing through the entire board. These holes are called blind vias when they connect an internal copper layer to an outer layer, or buried via when they connect two or more internal copper layers and no outer layers. The walls of the holes, for boards with or more layers, are made conductive then plated with copper to form plated through holes that electrically connect the conducting layers of the PCB. For multilayer boards, those with layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be remove by a chemical desmear process, or by plasma etch. Removing (etching back) the smear also reveals the interior conductors as well. Solder resist Areas that should not be soldered may be covered with a polymer solder resist (solder mask) coating. The solder resist prevents solder from bridging between conductors and creating short circuits. Solder resists also provide some protection from the environment. Solder resist is typically 20-30 micrometers thick.

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Screen printing Line art and text may be printed onto the outer surfaces of a PCB by screen printing. When space permits, the screen print text can indicate component designators, switch setting requirements, test points, and other features helpful in assembling, testing, and servicing the circuit board. Screen print is also known as the silk screen, or, in one sided PCBs, the red print. Lately some digital printing solutions have been developed to substitute the traditional screen printing process. This technology allows printing variable data onto the PCB, including serialization and barcode information for trace ability purpose. Test Unpopulated boards may be subjected to a bare board test where each circuit connection (as defined in a netlist) is verified as correct on the finished board. For high volume production, a bed of nails tester, a fixture or a rigid needle adapter is used to make contact with copper lands or holes on one or both sides of the board to facilitate testing. A computer will instruct the electrical test unit to apply a small voltage to each contact point on the bed-of-nails as required, and verify that such voltage appears at other appropriate contact points. A “short” on a board would be a connection where there should not be one; an “open” is between two points that should be connected but are not. For small or medium volume boards, flying probe and flying-grid testers use moving test heads to make contact with the copper/silver/gold/solder lands or holes to verify the electrical connectivity of the board under test. Another method for testing is industrial CT scanning, which can generate a 3D rendering of the board along with 2D image slices and can details such a soldered paths and connections. Printed circuit assembly After the printed circuit board (PCB) is completed, electronic components must be attached to form a functional printed circuit assembly, or PCA (sometimes called a “printed circuit board assembly” PCBA). In through hole construction, component leads are inserted in holes. In surface mount construction, the components are placed on pads or lands on the outer surfaces of the PCB. In both kinds of construction, component leads are electrically and mechanically fixed to the board with a molten metal solder.

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There are a variety of soldering techniques used to attach components to a PCB. High volume production is usually done with SMT placement machine and bulk wave soldering or reflow ovens, but skilled technicians are able to solder very tiny parts (for instance 0201 packages which are 0.02 in. by 0.01 in.) by hand under a microscope, using tweezers and a fine tip soldering iron for small volume prototypes. Some parts may be extremely difficult to solder by hand, such as BGA packages. Often, through holes and surface mount construction must be combined in a single assembly because some required components are available only in surfacemount packages, while others are available only in through hole packages. Another reason to use both methods is that through hole mounting can provide needed strength for components likely to endure physical stress, while components that are expected to go untouched will take up less space using surface mount techniques. After the board has been populated it may be tested in a variety of ways: 

While the power is off, visual inspection, automated optical inspection. JEDEC guidelines for PCB component placement, soldering, and inspection are commonly used to maintain quality control in this stage of PCB manufacturing.



While the power is off, analog signature analysis, power-off testing.



While the power is on, in circuit test, where physical measurements (i.e. voltage, frequency) can be done.



While the power is on, functional test, just checking if the PCB does what it had been designed to do. To facilitate these tests, PCBs may be designed with extra pads to make

temporary connections. Sometimes these pads must be isolated with resistors. The incircuit test may also exercise boundary scan test features of some components. Incircuit test systems may also be used to program nonvolatile memory components on the board. In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the PCB traces to test that the ICs are mounted correctly. Boundary scan testing requires that all the ICs to be tested use a standard test configuration procedure, the most common one being the Joint Test Action Group

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(JTAG) standard. The JTAG test architecture provides a means to test interconnects between integrated circuits on a board without using physical test probes. JTAG tool vendors provide various types of stimulus and sophisticated algorithms, not only to detect the failing nets, but also to isolate the faults to specific nets, devices, and pins. When boards fail the test, technicians may desolder and replace failed components, a task known as rework. Protection and packaging PCBs intended for extreme environments often have a conformal coating, which is applied by dipping or spraying after the components have been soldered. The coat prevents corrosion and leakage currents or shorting due to condensation. The earliest conformal coats were wax; modern conformal coats are usually dips of dilute solutions of silicon rubber, polyurethane, acrylic, or epoxy. Another technique for applying a conformal coating is for plastic to be sputtered onto the PCB in a vacuum chamber. The chief disadvantage of conformal coatings is that servicing of the board is rendered extremely difficult. Many assembled PCBs are static sensitive, and therefore must be placed in antistatic bags during transport. When handling these boards, the user must be grounded (earthed). Improper handling techniques might transmit an accumulated static charge through the board, damaging or destroying components. Even bare boards are sometimes static sensitive. Traces have become so fie that it’s quite possible to blow an etch off the board (or change its characteristics) with a static charge. This is especially true on nontraditional PCBs such as MCMs and microwave PCBs. 6.1.2 PCB Layout Of The Project

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Fig.6.1. PCB Layout 6.1.3 Soldering of the Components Soldering is the process of joining two or more similar or dissimilar metals by melting another metal having low melting point. Soldering Flux In order to make the surface accept the solder readily the component terminal should be free from oxides and other obstructing films. Soldering flux cleans the oxides from the surface of the metal. The leads should be cleaned chemically or by scrapping using a blade or a knife. Small amount of lead should be coated on the portion of the leads and the bit of the soldering iron. This process is called Tinning Zinc Chloride, Ammonium Chloride and Rosin are the most commonly used fluxes. These are available in petroleum jelly as paste flux. The residue which remains after the soldering may be washed out with more water accompanied by brushing.

Solder

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Solder is an alloy (mixture) of tin and lead, typically 60% tin and 40% lead. It melts at a temperature of about 20o C. Coating a surface with solder is called tinning because of the tin content of solder. Lead is poisonous and you should always wash your hands after using solder. Solder for electronics use contains tiny cores of flux, like the wires inside a mains flex. The flux is corrosive, like an acid, and it cleans the metal surfaces as the solder melts. This is why you melt the solder actually on the joint, not on the iron tip. Without flux most joints would fail because metals quickly oxidize and the solder itself will flow properly onto a dirty, oxidized, metal surface. The best size of solder for electronics circuit boards is 22 SWG (SWG – Standard Wire Gauge). For plugs, component holders and other larger joints you may prefer to use 18SWG solder. Soldering Tools Soldering Iron It is the tool used to melt the solder and apply at the joints in the circuits. It operates in 230V mains supply. The normal power ratings of the soldering iron are 10W, 25W, 35W, 65W and 125W. The iron bit at the top of its gets heated up within a few minutes. 10W and 25W soldering irons are sufficient for light duty works. Soldering Station The soldering station consists of a held hot air blow gun and the base station comprising of air flow and temperature controls to the hot air blow gun. Tip temperature is maintained by a feedback control loops. Soldering guns usually have a trigger switch which controls the AC power. Preparing the Soldering Iron Place the soldering iron in its stand and plug in. The iron will take a few minutes to reach its operating temperature of about 4000C. Dampen the sponge in the stand. The best way to do this is to lift it out the stand and hold it under a cold tap for a moment, then squeeze to remove excess water. It should be damp, not dripping wet. Wait a few minutes for the soldering iron to warm up. Check if it is ready by trying to melt a little solder on the tip. Wipe the tip of the iron on the damp sponge. This will clean the tip. Melt a little solder on the tip of the iron. This is called ‘tinning’ and it

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will help the heat to flow from the iron’s tip to the joint. It only needs to be done when you plug in the iron, and occasionally while soldering if you need to wipe the dip clean on the sponge. Making Soldered Joints Hold the soldering iron like a pen, near the base of the handle. Remember to never touch the hot element or tip. Touch the soldering iron onto the joint to be made. Make sure it touches both the component lead and the track. It should flow smoothly onto the lead and track to form a volcano shape. Make sure you apply the solder to the joint, not the iron. Remove the solder, then the iron, while keeping the joint still. Allow the joint a few seconds to cool before you move the circuit board. Inspect the joint closely. It should look shiny and have a ‘volcano’ shape. If not, you will need to reheat it and feed in a little more solder. This time ensure that both the lead and track are reheated fully before applying solder. Desoldering Using Desoldering Pump It is the removal of the solder from a previously soldered joint. There are two ways to remove the solder. Desolder pump is a commonly used device for this purpose. When the solder melts by the action of the soldering iron, a trigger on the de-solder pump should be activated to create a vacuum. Repeat if necessary to remove as much solder as possible. The pump will need emptying occasionally by unscrewing the nozzle. Desoldering Using Solder Remover Wick Apply both the end of the wick and the tip of your soldering iron to the joint. As the solder melts most of it will flow onto the wick, away from the joint. Remove the wick first, then the soldering iron. Cut off and discard the end of the wick coated with solder. After removing most of the solder from the joint(s) you may be able to remove the wire or component lead straight away (allow a few seconds for it to cool). If the joint will not come apart easily apply your soldering iron to melt the remaining traces.

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6.2 SOFTWARE REQUIREMENT 6.2.1 EDWIN XP EDWinXP or Electronic

Design

for

Windows is

a

commercially

available PCB design integrated CAD/CAE package. An electronic design engineer can use the computerized tools provided in EDWinXP to create an electronic circuit, design the PCB and fabricate PCBs. EDWinXP may be seen as a system of seamlessly integrated, task oriented, modules covering all stages of the design process from capturing the idea of a circuit in the form of a Schematic Diagram to generate a full set of documentation for manufacturing and assembling of PCBs. Additionally the package includes various validation tools ensuring correctness and integrity of designed circuits Complete design information is stored in the integrated project simultaneously accessible by Schematic Diagram Editor, PCB Layout Editor, Fabrication Output Manager and Simulators. This simulator provides EDWinXP users with the facility to analyze and validate the functionality and behaviour of circuits captured in the form of schematic diagrams. The EDSpice simulator is based on SPICE3F5 and XSPICE with

a

number

of

extensions

and

improvements.

The University

of

California developed SPICE3F5 and Georgia Tech Research Institute developed XSPICE. SPICE is well known in the electronic industry as general-purpose circuit simulation program for non linear DC, non-linear Transient and linear ac analysis. XSPICE extends SPICE3’s capabilities to allow simulation of mixed signal (analog/digital) and mixed level circuits. Front and back annotation of all design changes is fully automatic. EDWinXP comes with an extensive part library, which may be updated, customized and enhanced with the help of Library Editor. 6.3 WORKING OF PROJECT The circuit for the automatic speed controller for fans and coolers is shown in the figure. It has been designed to reduce the amount of electric power. In the circuit

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diagram IC1 (555 timer IC) act as an astable multivibrator. It is used to generate clock pulses. The pulses are fed to a decade divider counter, which is formed by IC2 and IC3. These ICs act as divide by 10 counters and divide by 9 counter respectively. The values of capacitors C1, resister R2 and R2 are so adjusted that the final output of IC3 goes high about 8hours. The first two outputs of IC3 (Q0 and Q1) are connected (0 Red) via diode D1 and D2 to the base of the transistor T1. Initially output Q0 is high and there for relay RL1 is energized. It remains energized when Q1 becomes high. The method of connecting the gadget of the fan or cooler is given in the figure. Initially the fan shall get A/C supply directly so it shall be run at high speed. When the output Q2 becomes high and Q1 becomes low, relay RL1 is turned off and relay RL2 is turned on. The fan gets A/C 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 activated thus the fan run at low speed. Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping T5 in saturation and relay RL4 is on. At the end of the cycle, when pin 11(Q9) becomes high T4 get saturated and T5 is cut off. Relay RL4 is switched off, thus switching of the fan or cooler. Using the given circuit 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 to Q4) is high, while at low speed it will run for a much longer time period when any of the four outputs(Q5 to Q8) is high. It is possible to make the fan run at the three speeds for an equal amount of time by connecting three terminal decoded outputs of IC3 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 IC3 to it.

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Fig.6.2 Developed System for Main Board

Fig.6.3 Developed System for An Intelligent Speed Governor for Fan

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CHAPTER 7 CONCLUSION AND FUTURE ENCHANCEMENT An Intelligent Speed Governor for fan is successfully implemented and demonstrated. The automatic speed controller for fans or coolers is used to control the speed automatically. We can also assign different time periods for each speed by designing the circuit to the need. By using this circuit the electric power can be saved to a greater extent and increase lifespan of fans and coolers. In future we can interface with microcontroller and can be modified to temperature controlled.

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REFERENCES [1]

B.Somanathan Nair: Digital Electronics and Logic Design, PHI. 2008

[2]

Gopakumar: Design and Analysis of Electronic Circuits, Phasor Book

[3]

Roy Chowdhary: Linear Integrated Circuits, 2/e, New age International

[4]

Behzad Razavi: Design of Analog CMOS IC, TMH, 2003

[5]

http://www.electronicschematics.com

[6]

http://www.electronics for you.com

[7]

http://www.diodes.com/datasheets/ds 1 n 4001.pdf

[8]

http://www.fairchildsemi.com/bs/NE/NE555.pdf

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APPENDIX

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Automatic Fan Speed Controller without micro controller OR An intelligent speed governor for fan

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