Week -2

AIM:

1. Make a Simulink model of Doorbell using solenoid block
2. To use a thermistor to sense the temperature of a heater & turn on or turn off the fan as per the condition.

STUDY 1:

The doorbell uses solenoid such that when switch is closed the circuit gets completed and electricity is passed into the solenoid which create a electromagnetic field. The plunger moves due to this electromagnetic field and hits the bell to produce sound.

SIMULINK MODEL:

EXPLANATION:

1. An input signal are Amplitude = 1, Period = 4sec Pulse Width = 50%, Phase delay = 0.
2. Battery is connected to the solenoid via switch. when the pulse generator creates an input signal its closes the switch and allow the current to flow into the solenoid.
3. The plunger part of solenoid is connected to the motion sensor to get the appropriate output of position of the plunger. A mechanical transalation reference is provided for the circuit.
4. The scope is connected to view the output from the motion sensor.

RESULT:

When the pluse generator amplitude is 1 , there is a movement is the plunger and when the amplitude returns to 0 the plunger moves to the original position. Due to low damping value it undergoes several oscillation before coming to the original position.

STUDY 2:

A thermistor is a resistance thermometer, or a resistor whose resistance is dependent on temperature. In PTC thermistor when temperature increases, the resistance increases, and when temperature decreases, resistance decreases. This type of thermistor is generally used as a fuse and in NTC thermistor when temperature increases, the resistance decreases, and when temperature decreases, resistance increases.

SIMULINK MODEL:

EXPLANATION:

1. A signal builder block is used to achieve the given temperature source (20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds)

2. Controlled Tempearature Source is an ideal energy source in a thermal network that can maintain a controlled temperature difference regardless of heat flow.

3. A NTC thermistor is used to sense the tempearature change .A reference resistor is used in series to measure the voltage drop change as temperature change.

4. Voltage sensor is used to measure the voltage drop and generate an output signal given to the logic circuit to turn on/off the fan.

SAMPLE TEMPERATURE CONDITIONS :

RESULTS:

The thermistor sense the temperature change if temperature increases the reference resistance increases causes increase in voltage drop across reference resistor.

When the temperature increases above 25 degree celcius (298k) switch is closed and fan starts opearting untill the tempearature decreases below 298k.