Apparatus:
NOT gate, thermistor (e.f. GM472 or VA 3404) variable resistor, power supply (6V), buzzer
Theory:
The thermistor is a device whose resistance changes by temperature. The resistance of a thermistor mases with increasing temperature. If we replace the LDR by a thermistor in the potential der circuit and apply it to NOT gate. We then have a temperature operated switch. When the mistor is under normal temperature, it has high enough to make the input of NOT gate at logic The output 0 and the alarm is not sounded. In case of fire, the higher temperature will cause the stance of the thermistor to decrease. The voltage V across thermistor decrease. When V is low gh to make the input of gate logic 0, the NOT gate will switch on and the alarm will end.
Procedure:
- Make connection according to circuit diagram.
- Adjust the voltage across the thermistor, so the point A is at logic 1(5V).
- Heat the thermistor until the resistance of thermistor decreases and voltage across thermistor decrease to make the point A at logic 0 and buzzer begins to sound.
Precaution:
- The connection should be neat and clean.
- 2 Adjust the voltage across thermistor carefully.
- Make use of bread board.
Viva Voce
Q1: What is a function of NOT gate?
Ans: It changes high voltage to low voltage and vice versa.
Q2: Can an inverter has more than and inputs?
Ans: No, it has only one input and one output.
Q3: What is the output when two NOT gate.
Ans: They have some output as input.
Q4: Can you make NOT gate using NAND gate
Ans: Yes, we can do it be combining input terminal of NAND gate.