Many circuits available in the market to measure temperature-using sensors like
transistor, AD590, LM337 or PT100. In this Project LM35DZ used as a temperature
sensor. Apart from displaying the temperature this circuit provides for temperature
based relay activation or controlling heaters, coolers or any electrical appliances.
The trip point temperature, set for activating the relay, can also be displayed
with a simple flick of a switch. This circuit canbe calibrated to have an accuracy
of +/- 0.5 Celcious with an operating range of 0 Celcious to 150 Celcious.
The circuit operates off a simple power supply using an IC 7805 regulator. A 12Vac
is rectified and filtered by using a bridge rectifier and filter capacitor. On the
+12V rail, a 7805 regulator is used to regulate the output to a stable 5V.
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LM35DZ Includes:-
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LM35DZ as a sensor used. It is a precision centigrade temperature sensor. We include
data sheet of LM35DZ. The output of LM35DZ is 10 mv per digree centrigrade. The
output of sensor is fed to ADC0804. ADC0804 is an 8 bit analog to digital converter
IC. Reference voltage for ADC0804 is set to 1.28V by D1, R22 and P1. The binary
output of ADC0804 id fed to port to of 89C51. Port 0 and port 2 of 89C51 is declared
as input port. Port 1 is a output port. Port 3 is used as a bidirectional port.
The output at set temperature is variable on pin no. 14 of controller. It is used
to drive a Darlington pair transistor form by Q4 and Q5. Display Dis1,Dis2, Dis3
are used to display the current or to set temperature. To display: C a, b, c, d
and pt. Pin of display DIS4 is grounded via register.
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Interface:-
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LCD based user inteface with ease of use use with microcontroller 8051.
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Preferred Technologies:
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8051 Microcontroller Based Programming and Circuitary
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About working of Project:
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The transformer is used in automatic voltage stabilizer is autotransformer is different
tapping, which consist of a single winding with tapping for input & output of power
supply. The secondary winding is 12V for the supply of control circuit and relay
operation. The tapping of the transformer is used for step-up & step-down of the
voltage. When variation of supply voltage occur. This voltage is applied to the
bridge circuit.
The diode used in the circuit is IN4007 6V. The IN4007 is a semiconductor silicon
rectifier diode which from a full wave rectifier circuit which makes flow current
in both side and gives D.C. voltage to the control circuit.
The capacitor has been derived from the word capacity to store electrons. A number
of different types of electric materials. Such as vacuums, plastic, glass, ceramic,
mica, aluminum oxide and tantalum oxide etc. the application of capacitor has also
been growing with continuous improvement in characteristic of capacitor due to for
blocking DC but also used for application such as filtering of electrical singles,
tuning, and capacitor is one of the most used components in electronic circuits.
In any circuit, the tendency of the circuit to oppose any charges in voltage is
define as its capacitance. Most digital logic circuits and processor need a 5V power
supply. To use these parts we need to build a regulated 5v source. Usually you start
with an urgently power supply ranging from 9V to 24V DC (a 12V power supply is included
with the microcontroller.). To make 5V power supply, we use a LM7805 voltage regulator
IC.
The LM7805 is simple to use. You simply connect the positive lead of your unregulated
DC power supply (anything from 5VDC) to the input port connected the negative lead
to the common port and then when you turn on the power, you get a 5V supply from
the output pin. The 5 voltage output is connected to the blue ground line of the
breadboard and a jumper wire is used to connected ground from there to the common
(ground) port of the 7805.
Now the IC 89C51 lower power high performance CMOS 8-Bit microcontroller with 4KB
of flash programmable and erasable read only memory. The device is manufactured
using Atmels’ high density non-violating memory technology. On-chip flash allows
the program memory to be re-programmed in system or by conventional no-volatile
memory programmer. By combining a versatile 8-bit CPU with flash on a monolithic
chip.
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