“THERMISTOR” (TEMPERATURE SENSING ALARM)

“THERMISTOR” (TEMPERATURE SENSING ALARM)

INTRODUCTION: This circuit is a temperature sensing alarm circuit. It activates an alarm whenever temperature rises above certain limits. Temperature control is very much essential in industries and some other places where temperature must be kept below certain levels so this circuit comes to the rescue in such sort of conditions.

CIRCUIT DIAGRAM:

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COMPONENTS:

Battery 6 Volts
Variable resistor 10 k
Resistor 120Ω,47K,54K,47K,1K
IC A quad Nand gat IC 4011
Transistors BC 547NPN
Capacitor 100µF
buzzer

WORKING: The element that plays a particular role in this circuit is Thermistor which senses the temperature of the environment. As the name implies THERMAL+RESISTOR (i-e: temperature of Thermistor varies as the temperature of the atmosphere varies) .The resistance of thermistor and the temperature of the atmosphere is inversely related (i-e: with increase in temperature outside the resistance of thermistor will decrease and vice versa) this makes it useful as a temperature sensor. The combinational circuit comprises of Nand gates which work as an oscillator circuit. Usually every combinational circuit posses some time delay between its input and output which has to avoided but in this case we make it useful as an oscillator. The circuit gets on and off repeatedly working as a square wave oscillator. Thus, this oscillator will activate the buzzer. The capacitors are installed in the circuit for filtration purpose hence ensuring stability and proper functioning.

APPLICATIONS: This circuit can be installed in all areas where temperature regulation is necessary such as: industries, cottages, garages, barns ware houses etc.

One Response to ““THERMISTOR” (TEMPERATURE SENSING ALARM)”

  1. January 31, 2016 at 5:48 am

    we get output exactly

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