Our sincerest appreciation must be extended …………………… We also want to thank

faculties of the College. They have been very kind and helpful to us. We want to thank all

teaching and non teaching staff to support us. Especially we are thankful to‐

………………………….for providing this golden opportunity to work on this project, inspiration

during the course of this project and to complete the project within Stipulated time duration

and four walls of …………………….We would like to express our sincere gratitude to our

Guides……………………….for their help during the course of the project right from selection of the

project, their constant encouragement, expert academic and practical guidance.

The PC processor generates very high temperature during its operation which is dissipated by the large heat sink placed above the processor. If the heat sink assembly is not tight with the processor or the cooling fan is not working, PC enters into the Thermal shutdown mode and will not boot up. If the PC is not entering into thermal shutdown, the high temperature can destroy the processor. This simple circuit can be placed inside the PC to monitor the temperature near the processor. It gives warning beeps when the temperature near the heat sink increases abnormally. This helps to shutdown the PC immediately before it enters into Thermal shutdown.Assemble the circuit on a general purpose PCB as compact as possible and enclose in a small box like junk mobile case. Use miniature 5v battery to make the gadget compact or small. the unit will give warning indication if pc overheated.

INDEX

NO. SUBJECT PAGE NO.

1. OVERVIEW OF PC TEMPERATURE ALARM………….…

2. CIRCUIT DIAGRAM AND DESCRIPTION OF CIRCUIT

DIAGRAM……..……………….…

3. WORKING OF PC TEMPERATURE ALARM……………...

4. COMPONENT LIST.…………………….….

5. PIN DIAGRAM OF IC…….………………....

6. DETAIL OF OTHER COMPONENTS…..…

7. APPLICATIONS …………………..……..….

8. LIMITATIONS …………………………….....

10. FUTURE WORK………………………….….

11. CONCLUSION ………..……………….……..

12. REFERENCE...…………………………..…...

The circuit uses a Piezo element (one used in Buzzer) as the heat sensor. The piezo crystals reorient when subjected to heat or mechanical stress and generates about one volt through the Direct piezoelectric property. IC1 is designed as a voltage sensor with both the inputs tied through the capacitor C1.The non inverting input is connected to the ground through R1

to keep the output low in the standby state. The inputs of IC1 are very sensitive and even a minute change in voltage level will change the output state.

In the standby mode, both the inputs of IC1 are balanced so that output remains low. When the Piezo element accepts heat, it generates a minute voltage which will upset the input balance and output swings high. This triggers LED and Buzzer. Capacitor C2 gives a short lag before the buzzer beeps to avoid false triggering. Warning beep continues till the piezo element cools.

CIRCUIT DIAGRAM OF PC TEMPERATURE

PIN CONFIGURATION OF IC LM35

Fig. 1 shows the circuit of the PCtemperature alarm and Fig. 2 showsthe pin configuration of sensor LM35.IC LM35 (IC1) is an easy-to-use temperature sensor. It is basically a three-terminal device (two supply leads plus the output) that operates over a wide supply range of 4 to 20V. It consumes only 56 μA at 5V and generates insignificant heat. IC2 is an operational amplifier used here as a voltage comparator. VR1 provides a reference voltage that can be set anywhere from 0V to approximately 1V, which matches the output voltage range of IC1. This reference voltage is input. Consequently, the output of IC2 is low if the output of IC1 is below the reference voltage, or high if the output of applied to the inverting input of IC2 and the output of IC1 is coupled to the non-inverting IC1 exceeds the reference voltage. The low-frequency oscillator IC3 is a standard 555 astable multivibrator circuit. It is gated via the reset input at pin 4, which holds output pin 3 low when IC3 is gated ‘off’ (when the output of IC2 is low). This prevents IC4 from oscillating. IC4 is another 555 astable multivibrator circuit, gated via its reset input. It has an operating frequency of approximately 2.5 kHz. When IC3 is activated, its output provides a square wave of 1 Hz. This is used to trigger IC4, which gives an audio output of 2.5 kHz in bursts. It is connected to loudspeaker LS1 to generate alarm.

The alarm circuit can be fitted into any spare expansion slot of the PC, but be careful to fit it the right way round. Before setting VR1 to a suitable threshold temperature, decide what

that temperature should be. The technical specification in your computer’s manual might be of help here. If we assume that the room temperature will not normally exceed 25oC, the temperature of the interior of the computer would be up to 35oC. Unless you have good reason to use a different threshold temperature, VR1should be set for a wiper potential of 350 mV. Trial-and-error method can be used in the absence of test equipment to enable VR1, but it would be a bit time-consuming. There is a computer’s outer casing must be at least partially removed to provide access to VR1. Once VR1 has been adjusted, the outer casing must be put back into place so that the interior of the computer can warm up in the normal way. You must therefore allow time for the temperature inside the computer to rise back to its normal operating level each time VR1 is readjusted. _

RESISTORS1.R1______10K2.R2______4.7K3.R3______2.2M4.R4______33K5.R5______330K6.R6______15K7.R7______47K

VARIABLE RESISTOR1.VR1____10K PRESET

CAPACITORS1.C1______10µ

2.C2______4.7µ3.C3______1µ4.C4______0.01µ5.C5______0.0047µ6.C6______0.01µ7.C7______220µ

IC’S1.IC1___IC LM352.IC2___IC CA31303.IC3___IC 5554.IC4___IC 555

SPEAKER1.LS1_____8Ω

POWER SUPPLY1.15 V POWER SUPPLY

HOW IC WORK?

ROLE OF IC CA 3130This IC is a 15 MHz BiMOS Operational amplifier with MOSFET inputs and Bipolar output. The inputs contain MOSFET transistors to provide very high input impedance and very low input current as low as 10pA. It has high speed of performance and suitable for low input current applications.

CA3130A and CA3130 are op amps that combine the advantage of both CMOS and bipolar transistors. Gate-protected P-Channel MOSFET (PMOS) transistors are used in the input circuit to provide very-high-input impedance, very-low-input current, and exceptional speed performance. The use of PMOS transistors in the input stage results in common-mode input-voltage capability down to0.5V below the negative-supply terminal, an important attribute in single-supply applications.A CMOS transistor-pair, capable of swinging the output voltage to within 10mV of either supply-voltage terminal (at very high values of load impedance), is employed as the output circuit.The CA3130 Series circuits operate at supply voltages ranging from 5V to 16V, (2.5V to 8V). They can be phase compensated with a single external capacitor, and have terminals for adjustment of offset voltage for applicationsrequiring offset-null capability. Terminal provisions are also made to permit strobing of the output stage. The CA3130A offers superior input characteristics over those of the CA3130.

Features• MOSFET Input Stage Provides:- Very High ZI = 1.5 T- Very Low current . . . . . . =5pA at 15V Operation• Ideal for Single-Supply Applications• Common-Mode Input-Voltage Range Includes Negative Supply Rail; Input Terminals can be Swung 0.5VBelow Negative Supply Rail • CMOS Output Stage Permits Signal Swing to Either (or both) Supply Rails

Applications• Ground-Referenced Single Supply Amplifiers• Fast Sample-Hold Amplifiers• Long-Duration Timers/ Mono stables• High-Input-Impedance Comparators (Ideal Interface with Digital CMOS)• High-Input-Impedance Wideband Amplifiers• Voltage Followers (e.g. Follower for Single-Supply D/A Converter )• Voltage Regulators (Permits Control of Output Voltage Down to 0V)• Peak Detectors• Single-Supply Full-Wave Precision Rectifiers• Photo-Diode Sensor Amplifiers

The NE555 IC is a highly stable controller capable of producing accurate timing pulses. With a monostable operation, the time delay is controlled by one external resistor and one capacitor. With an astable operation, the frequency and duty cycle are accurately controlled by two external resistors and one capacitor.

DETAILS OF PIN

1. Ground, is the input pin of the source of the negative DC voltage 2. trigger, negative input from the lower comparators (comparator B) that maintain

oscillation capacitor voltage in the lowest 1 / 3 Vcc and set RS flip-flop 3. output, the output pin of the IC 555. 4. reset, the pin that serves to reset the latch inside the IC to be influential to reset the

IC work. This pin is connected to a PNP-type transistor gate, so the transistor will be active if given a logic low. Normally this pin is connected directly to Vcc to prevent reset

5. control voltage, this pin serves to regulate the stability of the reference voltage negative input (comparator A). This pin can be left hanging, but to ensure the stability of the reference comparator A, usually associated with a capacitor of about 10nF to berorde pin ground

6. threshold, this pin is connected to the positive input (comparator A) which will reset the RS flip-flop when the voltage on the capacitor from exceeding 2 / 3 Vc

7. discharge, this pin is connected to an open collector transistor Q1 is connected to ground emitternya. Switching transistor serves to clamp the corresponding node to ground on the timing of certain

8. vcc, pin it to receive a DC voltage supply. Usually will work optimally if given a 5-15V. the current supply can be seen in the datasheet, which is about 10-15mA.

Features • High Current Drive Capability (200mA) • Adjustable Duty Cycle • Temperature Stability of 0.005%/C • Timing FromSec to Hours • Turn off Time Less Than 2Sec

Applications • Precision Timing • Pulse Generation • Time Delay Generation • Sequential Timing

LM35 Sensor Specification

The LM35 series are precision integrated-circuit LM35 temperature sensors, whose output

voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 sensor

thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is

not required to subtract a large constant voltage from its output to obtain convenient

Centigrade scaling. The LM35 sensor does not require any external calibration or trimming

to provide typical accuracies of ±¼°C at room temperature and ±¾°C over a full -55 to

+150°C temperature range. Low cost is assured by trimming and calibration at the wafer

level. The LM35's low output impedance, linear output, and precise inherent calibration

make interfacing to readout or control circuitry especially easy. It can be used with single

power supplies, or with plus and minus supplies. As it draws only 60 µA from its supply, it

has very low self-heating, less than 0.1°C in still air. The LM35 is rated to operate over a -

55° to +150°C temperature range, while the LM35C sensor is rated for a -40° to +110°C

range (-10° with improved accuracy). The LM35 series is available packaged in hermetic

TO-46 transistor packages, while the LM35C, LM35CA, and LM35D are also available in

the plastic TO-92 transistor package. The LM35D sensor is also available in an 8-lead

surface mount small outline package and a plastic TO-220 package.

LM35 Sensor Circuit Schematic

LM35 Sensor Pinouts and Packaging

LM35 Sensor Background and Applications

Most commonly-used electrical temperature sensors are difficult to apply. For example,

thermocouples have low output levels and require cold junction compensation. Thermistors

are nonlinear. In addition, the outputs of these sensors are not linearly proportional to any

temperature scale. Early monolithic sensors, such as the LM3911, LM134 and LM135,

overcame many of these difficulties, but their outputs are related to the Kelvin temperature

scale rather than the more popular Celsius and Fahrenheit scales. Fortunately, in 1983 two

I.C.’s, the LM34 Precision Fahrenheit Temperature Sensor and the LM35 Precision Celsius

Temperature Sensor, were introduced. This application note will discuss the LM34, but with

the proper scaling factors can easily be adapted to the LM35.

The LM35/LM34 has an output of 10 mV/°F with a typical nonlinearity of only ±0.35°F over a

−50 to +300°F temperature range, and is accurate to within ±0.4°F typically at room

temperature (77°F). The LM34’s low output impedance and linear output characteristic

make interfacing with readout or control circuitry easy. An inherent strength of the LM34

sensor over other currently available temperature sensors is that it is not as susceptible to

large errors in its output from low level leakage currents. For instance, many monolithic

temperature sensors have an output of only 1 μA/°K. This leads to a 1°K error for only 1 μ-

Ampere of leakage current. On the other hand, the LM34 sensor may be operated as a

current mode device providing 20 μA/°F of output current. The same 1 μA of leakage

current will cause an error in the LM34’s output of only 0.05°F (or 0.03°K after scaling).

Low cost and high accuracy are maintained by performing trimming and calibration

procedures at the wafer level. The device may be operated with either single or dual

supplies. With less than 70 μA of current drain, the LM34 sensor has very little self-heating

(less than 0.2°F in still air), and comes in a TO-46 metal can package, a SO-8 small outline

package and a TO-92 plastic package.

The LM35/LM34 is a versatile device which may be used for a wide variety of applications,

including oven controllers and remote temperature sensing. The device is easy to use

(there are only three terminals) and will be within 0.02°F of a surface to which it is either

glued or cemented. The TO-46 package allows the user to solder the sensor to a metal

surface, but in doing so, the GND pin will be at the same potential as that metal. For

applications where a steady reading is desired despite small changes in temperature, the

user can solder the TO-46 package to a thermal mass. Conversely, the thermal time

constant may be decreased to speed up response time by soldering the sensor to a small

heat fin

Three resistorsType Passive

Electronic symbol

(Europe)

(US)

A resistor is a two-terminalelectronic component that produces a voltage across its terminals that is proportional to the electric current through it in accordance with Ohm's law:

V = IR

Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel/chrome).The primary characteristics of a resistor are the resistance, the tolerance, maximum working voltage and the power rating. Other characteristics include temperature coefficient, noise, and inductance. Less well-known is critical resistance, the value below which power dissipation limits the maximum permitted current flow, and above which the limit is applied voltage. Critical resistance depends upon the materials constituting the resistor as well as its physical dimensions; it's determined by design.Resistors can be integrated into hybrid and printed circuits, as well as integrated circuits. Size, and position of leads (or terminals) are relevant to equipment designers; resistors must be physically large enough not to overheat when dissipating their power.

.

Capacitor

Modern capacitors, by a cm rule.

Type Passive

Invented Ewald Georg von Kleist (October 1745)

Electronic symbol

A capacitor or condenser is a passiveelectronic component consisting of a pair of conductors separated by a dielectric. When a voltagepotential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force between the plates. The effect is greatest between wide, flat, parallel, narrowly separated conductors.

An ideal capacitor is characterized by a single constant value, capacitance, which is measured in farads. This is the ratio of the electric charge on each conductor to the potential difference between them. In practice, the dielectric between the plates passes a small amount of leakage current. The conductors and leads introduce an equivalent series resistance and the dielectric has an electric field strength limit resulting in a breakdown voltage.

Capacitors are widely used in electronic circuits to block the flow of direct current while allowing alternating current to pass, to filter out interference, to smooth the output of power supplies, and for many other purposes. They are used in resonant circuits in radio frequency equipment to select particular frequencies from a signal with many frequencies.

(1)Ceramic capacitor

In electronics ceramic capacitor is a capacitor constructed of alternating layers of metal and ceramic, with the ceramic material acting as the dielectric. The temperature coefficient depends on whether the dielectric is Class 1 or Class 2. A ceramic capacitor (especially the class 2) often has high dissipation factor, high frequency coefficient of dissipation.

ceramic capacitors

A ceramic capacitor is a two-terminal, non-polar device. The classical ceramic capacitor is the "disc capacitor". This device pre-dates the transistor and was used extensively in vacuum-tube equipment (e.g., radio receivers) from about 1930 through the 1950s, and in

discrete transistor equipment from the 1950s through the 1980s. As of 2007, ceramic disc capacitors are in widespread use in electronic equipment, providing high capacity & small size at low price compared to other low value capacitor types.

Ceramic capacitors come in various shapes and styles, including:

disc, resin coated, with through-hole leads multilayer rectangular block, surface mount bare leadless disc, sits in a slot in the PCB and is soldered in place, used for UHF

applications tube shape, not popular now

(2)Electrolytic capacitor

Axial lead (top) and radial lead (bottom) electrolytic capacitors

An electrolytic capacitor is a type of capacitor that uses an ionic conducting liquid as one of its plates with a larger capacitance per unit volume than other types. They are valuable in relatively high-current and low-frequency electrical circuits. This is especially the case in power-supply filters, where they store charge needed to moderate output voltage and current fluctuations in rectifier output. They are also widely used as coupling capacitors in circuits where AC should be conducted but DC should not.

Electrolytic capacitors can have a very high capacitance, allowing filters made with them to have very low corner frequencies.

Light-emitting diode

Type Passive, optoelectronic

Working principle Electroluminescence

Invented Nick Holonyak Jr. (1962)

Electronic symbol

Pin configuration Anode and Cathode

A light-emitting diode (LED) is an electronic light source. LEDs are used as indicator lamps in many kinds of electronics and increasingly for lighting. LEDs work by the effect of electroluminescence, discovered by accident in 1907. The LED was introduced as a practical electronic component in 1962. All early devices emitted low-intensity red light, but modern LEDs are available across the visible, ultraviolet and infra red wavelengths, with very high brightness.

LEDs are based on the semiconductor diode. When the diode is forward biased (switched on), electrons are able to recombine with holes and energy is released in the form of light. This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. The LED is usually small in area (less than 1 mm2) with integrated optical components to shape its radiation pattern and assist in reflection.[3]

LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.

Applications of LEDs are diverse. They are used as low-energy indicators but also for replacements for traditional light sources in general lighting, automotive lighting and traffic signals. The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in communications technology.

Various types LEDs

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