TACHOMETER USING FREQUENCY TO VOLTAGE CONVERTER

7/25/2019 TACHOMETER USING FREQUENCY TO VOLTAGE CONVERTER

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TACHOMETER USING FREQUENCY TO VOLTAGE CONVERTER

Rajadhani Institute of Engineering and Technology 1

CHAPTER 1

INTRODUCTION

Tachometers or revolution counters on cars, aircraft, and other vehicles show the rate ofrotation of the engine's crankshaft, and typically have markings indicating a safe range of

rotation speeds. This can assist the driver in selecting appropriate throttle and gear settings for

the driving conditions. Prolonged use at high speeds may cause inadequate lubrication,

overheating (exceeding capability of the cooling system), exceeding speed capability of sub-parts

of the engine (for example spring retracted valves) thus causing excessive wear or permanent

damage or failure of engines. This is more applicable to manual transmissions than to

automatics. On analogue tachometers, speeds above maximum safe operating speed are typically

indicated by an area of the gauge marked in red, giving rise to the expression of "redlining" an

engine revving the engine up to the maximum safe limit. The red zone is superfluous on most

modern[specify]

cars, since their engines typically have a revolution limiter which electronically

limits engine speed to prevent damage. Diesel engines with traditional mechanical injector

systems have an integral governor which prevents over-speeding the engine, so the tachometers

in vehicles and machinery fitted with such engines sometimes lack a redline.

In vehicles such as tractors and trucks, the tachometer often has other markings, usually a

green arc showing the speed range in which the engine produces maximum torque, which is of

prime interest to operators of such vehicles. Tractors fitted with a power take off (PTO) system

have tachometers showing the engine speed needed to rotate the PTO at the standardized speed

required by most PTO-driven implements. In many countries, tractors are required to have

a speedometer for use on a road. To save fitting a second dial, the vehicle's tachometer is often

marked with a second scale in units of speed. This scale is only accurate in a certain gear, but

since many tractors only have one gear that is practical for use on-road, this is sufficient.

Tractors with multiple 'road gears' often have tachometers with more than one speed scale.

Aircraft tachometers have a green arc showing the engine's designed cruising speed range.

In older vehicles, the tachometer is driven by the RMS voltage waves from the low tension (LT)

side of the ignition coil,[2]

while on others (and nearly all diesel engines, which have no ignition

system) engine speed is determined by the frequency from the alternator tachometer output. This


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is from a special connection called an "AC tap" which is a connection to one of the stator's coil

output, before the rectifier. Tachometers driven by a rotating cable from a drive unit fitted to the

engine (usually on the camshaft) exist - usually on simple diesel-engined machinery with basic

or no electrical systems. On recent EMSfound on modern vehicles, the signal for the tachometer

is usually generated from an ECU which derives the information from either the crankshaft or

camshaft speed sensor.

In this project, we are developing a simple tachometer using a frequency to voltage

converter using BC337 and LM555. Here the LM555 is used as monostable multivibrator. The

entire circuit work like an amplitude modulation circuit in communication systems. ie; the

amplitude of carrier wave (here it is pulses produced by monostable multivibrator ) is modulated

as the variations in input frequency.

Now we are connecting the input terminal to the spark plug cable and terminal common

point should be connected to the vehicles ground.

Gasoline or petrol engines are also known as spark-ignition (S.I.) engines. Petrol engines

take in a flammable mixture of air and petrol which is ignited by a timed spark when the charge

is compressed. The first four stroke spark-ignition (S.I.) engine was built in 1876 by Nicolaus

August Otto, a self-taught German engineer at the Gas-motoreufabrik Deutz factory near

Cologne, for many years the largest manufacturer of internal-combustion engines in the world. It

was one of Otto's associates - Gottlieb Daimler - who later developed an engine to run on petrol

which was described in patent number 4315 of 1885. He also pioneered its application to the

motor vehicle

Four stroke Spark-ignition (S.I) engines require four piston strokes to complete one

cycle: an air-and-fuel intake stroke moving outward from the cylinder head, an inward

movement towards the cylinder head compressing the charge, an outward power stroke, and an

inward exhaust stroke.

Induction stroke(Fig. 1.11) The inlet valve is opened and the exhaust valve is closed. The piston

descends, moving away from the cylinder head (Fig. 1.11). The speed of the piston moving along

the cylinder creates a pressure reduction or depression which reaches a maximum of about 0.3

bar below atmospheric pressure at one-third from the beginning of the stroke. The depression


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actually generated will depend on the speed and load experienced by the engine, but a typical

average value might be 0.12 bar below atmospheric pressure. This depression induces (sucks in)

a fresh charge of air and atomized petrol in proportions ranging from 10 to 17 parts of air to one

part of petrol by weight.

Fig 1.1Induction stroke

An engine which induces fresh charge by means of a depression in the cylinder is said to be

'normally aspirated' or 'naturally aspirated'.

Compression stroke (Fig. 1.12) Both the inlet and the exhaust valves are closed. The piston

begins to ascend towards the cylinder head (Fig. 1.12). The induced air-and-petrol charge is

progressively compressed to something of the order of one-eighth to one-tenth of the cylinder's

original volume at the piston's innermost position. This compression squeezes the air and

atomized-petrol molecules closer together and not only increases the charge pressure in the


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cylinder but also raises the temperature. Typical maximum cylinder compression pressures will

range between 8 and 14 bar with the throttle open and the engine running under load.

Fig 1.2 Compression stroke

Power stroke (Fig. 1.13) Both the inlet and the exhaust valves are closed and, just before the

piston approaches the top of its stroke during compression, a spark-plug ignites the dense

combustible charge (Fig. 1.13). By the time the piston reaches the innermost point of its stroke,

the charge mixture begins to burn, generates heat, and rapidly raises the pressure in the cylinder

until the gas forces exceed the resisting load. The burning gases then expand and so change the

piston's direction of motion and push it to its outermost position. The cylinder pressure then

drops from a peak value of about 60 bar under full load down to maybe 4 bar near the outermost

movement of the piston.


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Fig 1.3 Power stroke

Exhaust stroke(Fig. 1.14) At the end of the power stroke the inlet valve remains closed but the

exhaust valve is opened. The piston changes its direction of motion and now moves from the

outermost to the innermost position (Fig. 1.14). Most of the burnt gases will be expelled by the

existing pressure energy of the gas, but the returning piston will push the last of the spent gases

out of the cylinder through the exhaust-valve port and to the atmosphere. During the exhaust

stroke, the gas pressure in the cylinder will fall from the exhaust-valve opening pressure (which

may vary from 2 to 5 bar, depending on the engine speed and the throttle-opening position) to

atmospheric pressure or even less as the piston nears the innermost position towards the cylinder

head


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.

Fig 1.4 Exhaust stroke


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CHAPTER 2

HARDWARE DESCRIPTION

2.1 BLOCK DIAGRAM

Fig 2.1 Block diagram

The input of the circuit is connected to the spark plug and ground to the ground of

vehicle. Input from sparkplug enters to the RC High Pass Filter. Then it proceeds to switching

circuit. The switching circuit consists of a diode a npn transistor and a capacitor. Diode will

eliminate the lower part of the signal. There is a parallel path to ground through a npn transistor

and capacitor. The transistor is acting as switch. At high pulse the transistor will conducts from

Vcc to ground. At low voltage transistor do not conducts, so the capacitor C2 charges. At next

pulse Vcc grounds through transistor and capacitor discharges to trigger pin of 555 timer. 555

timer is in monostable mode. The output of monostable passes through a RC integrator and the

integrator varies the output voltage with respect to time delay.


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Rajadhani Institute of Engineering an

2.2 CIRCUIT DIAGRAM

Fig 2.2 Circuit Diagram for

2.3 COMPONENT DETAI

2.3.1 RESISTOR

The flow of charge throu

respects to mechanical friction.

electric circuit resistance is deli

three categories, only two of

resistor. The third category is

vitreous paint finish of the com

letter omega () looks as an u

make them work properly and

different types of resistors avail

given in K and M. Resistor

high as 10 M . The figure 2.31

TACHOMETER USING FREQUENCY TO VO

Technology

Tachometer using Frequency to voltage conver

S

gh any material encounters an opposing force si

his opposing force is called resistance of the

erately introduced in the form of resistor. Res

hich are color coded which are metal films

wire wound type, where values are generall

onent. Unit of resistance is ohms and is repr

turned horseshoe. Most electronic circuit req

it is obliviously important to find out som

able. 1 is quite small for electronics so resi

used in electronics can have resistances as lo

shows resistors.

LTAGE CONVERTER

8

er

milar to in many

aterial. In some

istor used fall in

and carbon film

printed on the

sented in Greek

ires resistors to

thing about the

tances are often

w as 0.1 or as


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2.3.2 CAPACITOR

In a way, a capacitor is

way, capacitor and batteries bot

produce electrons on one termi

capacitor has two terminals. Ins

metal plates separated by dielect

does not conduct electricity and

capacitor to battery, the plate on

accepts electrons that the batter

positive terminal of the battery l

The figure 2.32 shows capaciors.

Fig 2.3


Technology

a little like a battery. Although they work co

h store electrical energy. Inside the battery, c

al and absorb electrons at the other terminal.

de the capacitor, the capacitor, the terminals

ric. The dielectric can be air, paper, plastic or a

keeps the plates from touching each other. W

the capacitor that attaches to the negative termi

y is producing. The plate on the capacitor tha

ses electrons to battery. Three capacitors are u

: Resistors

LTAGE CONVERTER

9

pletely different

emical reactions

ike a battery, a

onnected to two

nything else that

en you connects

al of the battery

t attaches to the

ed in the circuit.


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10

2.3.3 555 TIMER IC

The 555 timer IC is a

generation, and oscillator applic

an oscillator, and as a flip-flop

package.

Depending on the man

2 diodes and 15 resistors on a sil

8). Variants available include th

two 558 & 559s (both a 16-pin

connected internally, and TR is

Fig


Technology

integrated circuit (chip) used in a variety

ations. The 555 can be used to provide

element. Derivatives provide up to four timin

ufacturer, the standard 555 package includ

icon chip installed in an 8-pin mini dual-in-lin

556 (a 14-pin DIP combining two 555s on o

DIP combining four slightly modified 555s

alling edge sensitive instead of level sensitive).

2.4 : Capacitors

LTAGE CONVERTER

of timer, pulse

time delays, as

circuits in one

s 25 transistors,

e package (DIP-

e chip), and the

ith DIS & THR


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11

Fig 2.


Technology

5 Internal block diagram 555

Fig 2.6Pinout diagram

LTAGE CONVERTER


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Rajadhani Institute of Engineering and Technology

12

The connection of the pins for a DIP package is as follows:

Table 2.1 Connection of the pins for a 555 DIP package

Pin Name Purpose

1 GND Ground reference voltage, low level (0 V)

2 TRIG

The OUT pin goes high and a timing interval starts when this input falls below

1/2 of CTRL voltage (which is typically 1/3 VCC, CTRL being 2/3 VCCby default

if CTRL is left open).

3 OUT This output is driven to approximately 1.7 V below +VCC, or to GND.

4 RESET

A timing interval may be reset by driving this input to GND, but the timing does

not begin again until RESET rises above approximately 0.7 volts. Overrides

TRIG which overrides THR.

5 CTRL Provides "control" access to the internal voltage divider (by default, 2/3 VCC).

6 THRThe timing (OUT high) interval ends when the voltage at THR ("threshold") isgreater than that at CTRL (2/3 VCCif CTRL is open).

7 DISOpen collector output which may discharge a capacitor between intervals. In

phase with output.

8 VCCPositive supply voltage, which is usually between 3 and 15 V depending on the

variation.

Pin 5 is also sometimes called the CONTROL VOLTAGE pin. By applying a voltage to

the CONTROL VOLTAGE input one can alter the timing characteristics of the device. In most

applications, the CONTROL VOLTAGE input is not used. It is usual to connect a 10 nF

capacitor between pin 5 and 0 V to prevent interference. The CONTROL VOLTAGE input can

be used to build an astable multivibrator with a frequency-modulated output.


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13

The IC 555 has three operating modes:

1. Bistable mode or Schmitt trigger the 555 can operate as a flip-flop, if the DIS pin is not

connected and no capacitor is used. Uses include bounce-free latched switches.2. Monostable mode in this mode, the 555 functions as a "one-shot" pulse generator.

Applications include timers, missing pulse detection, bounce-free switches, touch

switches, frequency divider, capacitance measurement, pulse-width modulation (PWM)

and so on.

3.

Astable (free-running) mode the 555 can operate as an electronic oscillator. Uses

include LED and lamp flashers, pulse generation, logic clocks, tone generation, security

alarms, pulse position modulation and so on. The 555 can be used as a simple ADC,

converting an analog value to a pulse length (e.g., selecting a thermistor as timing

resistor allows the use of the 555 in a temperature sensor and the period of the output

pulse is determined by the temperature). The use of a microprocessor-based circuit can

then convert the pulse period to temperature, linearize it and even provide calibration

means.

SPECIFICATIONS

Table 2.3 SPECIFICATIONS OF NE555

Supply voltage (VCC) 4.5 to 15 V

Supply current (VCC= +5 V) 3 to 6 mA

Supply current (VCC= +15 V) 10 to 15 mA


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14

Output current (maximum) 200 mA

Maximum Power dissipation 600 mW

Power consumption (minimum operating) 30 mW@5V, 225 mW@15V

Operating temperature 0 to 75 C

2.3.4 BC337 TRANSISTOR

The BC337 is a NPN General purpose transister.

FEATURES

High current (max. 500 mA)

Low voltage (max. 45 V).

APPLICATIONS

General purpose switching and amplification,

e.g. driver and output stages of audio amplifiers.

DESCRIPTION

NPN transistor in a TO-92; SOT54 plastic package.

PNP complement: BC327.


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15

Fig 2.7BC337

Fig 2.8NPN TRANSISTOR

2.3.5 ZENER DIODE 1N4148

The 1N4148 is a standard silicon switching diode. It is one of the most popular and long-

lived switching diodes because of its dependable specifications and low cost.. The 1N4148 is

useful in switching applications up to about 100 MHz with a reverse-recovery time of no more

than 4 ns. The 1N4148 comes in a DO-35 glass package for through-hole mounting. This is

useful for breadboarding of circuits. A surface mount device, 1N4148WS, is available in a

plastic SOD package.

SPECIFICATIONS

VRRM= 75-100 V maximum repetitive reverse voltage

IO= 75-200 mA average rectified forward current


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IF= 200-300 mA maximum direct forward current

VF= 1.0 V at 10 mA.[7]

IFSM= 1.0 A (pulse width = 1 s), 4.0 A (pulse width = 1 s) non-repetitive peak forward

surge current

PD= 500 mW power dissipation

TRR< 4 ns reverse-recovery time

Fig 2.9 ZENER DIODE 1N4148

2.3.6 ANALOG VOLTMETER

Avoltmeter

is an instrument used for measuring electrical potential difference betweentwo points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to

the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an

analog to digital converter.

A moving coil galvanometer can be used as a voltmeter by inserting

a resistor in series with the instrument. The galvanometer has a coil of fine wire suspended in a

strong magnetic field. When an electric current is applied, the interaction of the magnetic field of

the coil and of the stationary magnet creates a torque, tending to make the coil rotate. The torqueis proportional to the current through the coil. The coil rotates, compressing a spring that opposes

the rotation. The deflection of the coil is thus proportional to the current, which in turn is

proportional to the applied voltage, which is indicated by a pointer on a scale.


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17

Fig 2.10 Analog Voltmeter

One of the design objectives of the instrument is to disturb the circuit as little as possible

and so the instrument should draw a minimum of current to operate. This is achieved by using a

sensitive galvanometer in series with a high resistance.

The sensitivity of such a meter can be expressed as "ohms per volt", the number of ohms

resistance in the meter circuit divided by the full scale measured value. For example, a meterwith a sensitivity of 1000 ohms per volt would draw 1 milliampere at full scale voltage; if the

full scale was 200 volts, the resistance at the instrument's terminals would be 200,000 ohms and

at full scale the meter would draw 1 milliampere from the circuit under test. For multi-range

instruments, the input resistance varies as the instrument is switched to different ranges.

Moving-coil instruments with a permanent-magnet field respond only to direct current.

Measurement of AC voltage requires a rectifier in the circuit so that the coil deflects in only one

direction. Moving-coil instruments are also made with the zero position in the middle of the scaleinstead of at one end; these are useful if the voltage reverses its polarity.

Voltmeters operating on the electrostatic principle use the mutual repulsion between two charged

plates to deflect a pointer attached to a spring. Meters of this type draw negligible current but are

sensitive to voltages over about 100 volts and work with either alternating or direct current.


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CHAPTER 3

PCB FABRICATION

3.1 PCB DESIGNING

A printed circuit board, or PCB, is used to mechanically support and electrically

connect electronic components using conductive path ways, tracks or traces etched from copper

sheets laminated onto a non-conductive substrate. It is also referred to a sprinted writing board

(PWD) or etched writing board. A PCB populated with electronic components is a printed circuit

assembly (PCA) also known as a printed circuit board assembly (PCBA) PCBs are inexpensive,

and can be highly reliable. They require much more layout effort and higher initial cost than

either wire-wrapped or point-to-point constructed circuits, but are much cheaper and faster for

high-volume production. Much of the electronics industrys PCB design assembly, quality

control needs are set by standards that are published by the IPC organization.

3.2 PCB MANUFACTURING

1. Pattern /Etching:

The majority of printed circuit boards are manufactured by applying a layer of

copper over the entire surface of the circuit board substrate either on one side or both sides. This

creates what is referred to as a blank printed circuit board, meaning the copper is everywhere on

the surface. From here the unwanted areas are removed, this is called a subtractive method, the

most common subtractive method is known as a photoengraving.

2. Photoengraving:

The photoengraving process uses a mask or photo mask combined with chemical

etching to subtract the copper areas from the circuit board substrate. The photo mask is created

with a photo plotter which takes the design from a CAD PCB software program. Lower

resolution photo masks are sometimes crated with the use of a laser printer using a transparency.


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3. Lamination:

Many printed circuit boards are made up of multiple layers; these are referred to

as multi-layer printed circuit boards. They consist of several thin etched boards or trace layers

and are bonded together through the process of lamination.

4.Testing:

Unpopulated circuit boards are subjected to bare board test where each circuit

connection (as defined in a net list) is verified as correct on the finished circuit board. In high

volume circuit board production, a bed of nails tester or fixture is used to make contact with the

copper lands or holes on one or both sides of the board to facilitate testing. Computers are used

to control the electrical testing unit to send a small current through each contact point on the bed

of nails and verify that such current can be detected on the appropriate contact points.

1. Drilling:

Each layer of the printed circuit board requires the ability of one layer to connect

to another; this is achieved through drilling small holes called VIAS. These drilled holes

require precision placement and most commonly done with the use of an automated drilling

machine. These machines are driven by computer programs and files called numerically

controlled drill (NCD) files also referred to as excellent files. These files determine the position

and size of each file in the design.

3.3 SOLDERING PRECAUTIONS

The tip of soldering iron was kept clean with the help of a file from time to time.

The solder wire was of smaller thickness.

Extra solder was not used in order to avoid a cause of short circuit in the conductive

path.

The overheating of components was avoided to prevent component damage as a result

of excessive heat on the components due to the heat from the soldering iron.

The leads of the components were kept clean before soldering, with the use of sand

paper.


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Fig 3.1 Soldering kit


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CHAPTER 4

ADVANTAGES AND APPLICATIONS

Frequency-to-voltage converters are used in a variety of industries and applications. Forexample

1.

Vehicle-monitoring applications use frequency-to-voltage converters to evaluate the

response times of clutches

2. Air-conditioning compressors and anti-lock braking systems.

3. Driveline analysis and to monitor and control engine speeds.

4.

Flowmeter monitoring

5. Machine analysis and control

6. Response time evaluation.


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CHAPTER 5

RESULTS

Here we can consider the graph for our the frequency to voltage converter from the

following table

At

Vcc = 12V

Vin = 20V

Table 5.11 FREQUENCY TO VOLAGE


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Fig5.1 Frequency to Voltage graph

The graph shows a linear variation for a wide range and is in our required range of operation.

RPM at a certain frequency = (frequency in Hertz 60 ) 2

(this is for a four stroke engine)


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CHAPTER 6

CONCLUSION

The framework of the proposed system is developed for a tachometer suitable for

automobiles using a frequency to voltage converter. A tachometer is an instrument measuring the

rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays

the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are

increasingly common.

From our observation it is clear that the variation of output voltage with frequency is

linear. The calculation of the RPM of the vehicle from the frequency is so very easy, because the

RPM directly proportional to the linearly varying voltage.


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REFERENCES

[I] H. Berlin; 555 Timer Applications Sourcebook Experiments; BPB Publications

[II] Forrest Mims III; Timer, Op Amp, and Optoelectronic Circuits and Projects; Master

Publishing.

[III] Forrest Mims III; Radio Shack; Engineer's Mini-Notebook 555 Timer IC Circuits [4]IC

Timer Cookbook; 2nd Ed; Walter G Jung; Sams Publishing

[IV]Jonathan Oxer and Hugh Blemings (2009). Practical Arduino: Cool Projects for Open

Source Hardware.

[V] Michael Gasperi, Philippe E. Hurbain, and Philippe Hurbain (2009). Extreme NXT:

Extending the Lego Mindstorms NXT to the Next Level (2nd ed.).

[VI] The Semiconctor Data Library (Fourth ed.). Motorola Semiconductor Products, Inc. 1973.

TACHOMETER USING FREQUENCY TO VOLTAGE CONVERTER

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