05-05-2012, 12:52 PM
AUTOMATIC TEMPERATURE CONTROLLER
AUTOMATIC TEMPERATURE CONTROLLER.docx (Size: 510.63 KB / Downloads: 52)
INTRODUCTION
Most of the electrical appliances (Like electric water heaters , irons….etc) are getting short-circuited , due to the increase in the temperature limits (beyond the range they are mentioned). The increase in temperature is mainly dependent on the usage of the appliance. As temperature goes on increasing , the current consumption also increases ( this causes waste usage of current .)
In order to main-tains the temperature in any electrical appliances in desired limits ,“AUTOMATIC TEMPERATURE CONTROLLER” circuit is preferable . This circuit automatically controls the temperature . These temperature limits are controlled by the potentiometers and load is connected by the relays. The principle here is when the temperature of the load increases then automatically gets OFF and after some time when temperature limits decreases automatically gets ON.
IC 555 is used as an timer in this circuit and this IC 555 gives the supply to the diode. The zener diode D4 gives the supply to the T3 trnsistor from the timer IC 555. IC78712 is used as an voltage regulator, in this circuit the supply is given to ICs through this IC 7812 . IC 7812 plays a major role in maintaining the temperature limits.
CIRCUIT DESCRIPTION:
• The circuit will be driven by 12V , the supply input voltage given to the circuit (from RPS) is 18V.
• The input voltage 18V is regulated by voltage regulator IC7812 and gives the standard output voltage 12V (which is sufficient for maintenance of the circuit).
• The Relay plays an important role in controlling the temperature of load .
• The IC LM324 helps in maintaining the voltage limits and sensitivity of the resistance is controlled by the potentiometers .
• As thermistors are heat sensitive devices it senses the increase in temperature of the load .
• The timer IC 555 is useful for setting the time of load to work in ON and OF conditions
CHAPTER -3
COMPONENTS DESCRIPTION
3.1 LM324
3.1.1 General Description:
The LM324 series consists of four independent, high gain,internally frequency compensated operational amplifierswhich were designed specifically to operate from a single power supply over a wide range of voltages. Operation from split power supplies is also possible and the low power supply current drain is independent of the magnitude of the power supply voltage.
Application areas include transducer amplifiers, DC gain blocks and all the conventional op amp circuits which now can be more easily implemented in single power supply systems. For example, the LM324 series can be directly operated off of the standard +5V power supply voltage which is used in digital systems and will easily provide the required interface electronics without requiring the additional ±15V power supplies.
3.1.2 Unique Characteristics
• In the linear mode the input common-mode voltage range includes ground and the output voltage can also swing to ground, even though operated from only a single power supply voltage .
• The unity gain cross frequency is temperature Compensated .The input bias current is also temperature.
3.1.3 Features
• Internally frequency compensated for unity gain.
• Large DC voltage gain 100 dB.
• Wide bandwidth (unity gain) 1 0MHz (temperature compensated).
• Wide power supply range:
Single supply 3V to 32V or dual supplies ±1.5V to ±16V.
• Very low supply current drain (700 μA)—essentially independent of supply voltage.
• Low input biasing current 45 nA (temperature compensated).
• Low input offset voltage 2 mV and offset current: 5 nA.
• Input common-mode voltage range includes ground.
• Differential input voltage range equal to the power supply voltage.
• Large output voltage swing 0V to V+ − 1.5Vnsated.