PRESENTATION ON WATER TEMPERATURE CONTROLLER by saad

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PRESENTATION ON WATER TEMPERATURE CONTROLLER:

PRESENTATION ON WATER TEMPERATURE CONTROLLER BY - SAAD KHAN ROLL. NO.- 13

INTRODUCTION OF WATER TEMPERATURE CONTROLLER:

INTRODUCTION OF WATER TEMPERATURE CONTROLLER This circuit controls as well as indicates it on the LED bar graph. Initially when temp. of water is 0 degree, none of the LED glows. But as the temperature starts increasing above 30 degree, LED’s from LED1 to LED8 starts glowing one after the others. When the temperature is around 30 degree, only one LED is glowing and as the temp. reaches around 97 degree all the LED’s will be glowing.

CIRCUIT DIAGRAM OF WATER TEMPERATUE CONTROLLER:

CIRCUIT DIAGRAM OF WATER TEMPERATUE CONTROLLER

CONSTRUCTION :

CONSTRUCTION To detect the temp. of water, PT100 is the commonly used RTD. It is connected to one arm of the Wheatstone bridge and has a resistance of 100 ohms at surrounding temp. 0 deg. Ideally at 0 deg., the bridge has to be in unbalanced condition and for all the other temp, it will remain the same. The unbalanced voltage of the bridge is converted into suitable range of 0v to 5v by the Instrumentation amplifier group IC1 to IC3. Output of Instrumentation amplifier is coupled to voltage comparators for driving the display LED’s.

EXPLANATION:

EXPLANATION Initially immerse the RTD in ice cold water and adjust preset VR1 such that the bridge becomes balance and IC3 becomes 0V. Next, immerse the RTD in boiling water and adjust VR2 such that the IC3 becomes 6V. Repeat this for four to five times. To control the temperature of water, on/off type controller is used. Lower threshold point is set at 80deg., while upper threshold point is set at 97deg. An electric heater coil is used for heating the water. The supply is switched on the heater heats the water up to 80deg., o/p of IC5 goes high. This turns on relay driver transistor T1 to energize relay RL1. In this state relay RL2 is in off condition. When the temperature of water crosses 97deg. o/p of IC5 goes high. This make transistor T2 on which in turn energizes relay RL2.

Slide 6:

Relay RL2 in energized state cuts of power supply to the heater coil. Relay RL2, once energized remain so due to the latching arrangement provided by its second pair of contacts. Simultaneously the buzzer also sounds , due to forward biasing of T3. Since the supply is cut- off the temp. of water starts decreasing. Gradually the buzzer goes off, as the output of IC5 goes low. When the temp. goes below 80deg., o/p of IC5 goes low to turn off T1 and RL1. As a result, the power supply provided to RL2 is cut off and RL2 de- energizes. This will again turn on the main supply to the heater coil. Once again, the temp. of water starts increasing and the cycle repeats to maintain water temp. within the limit 80deg to 97deg.

APPLICATIONS:

APPLICATIONS This controller can be used to control the temperature of water in water heaters, heaters, boilers etc.

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