Week -2

Solution1: The simulink model for the doorbell usin a solenoid has been attached below. The switch used in the model is being contolled by a physical signal using a pulse generator so that it remains ON for a period of 2 seconds periodically over the entire time range of 12 seconds. As the switch becomes ON the circuit of solenoid gets completed and hence it is energised.Due to this an attractive force pulls the plunger towards point C.As long as the circuit is closed, the plunger remains in to and fro motion due to the mechanical damping .As the energy in the coil reaches its peak value then the solenoid starts discharging and the direction of force gets reversed.This process continues in the ON duraton of 2 seconds. The ON and OFF instants of the switch are:-

ON- t=(2,6,10s)

OFF- t=(0,4,8,12s)

The graphs showing displacement and velocity of plunger along with the simulink model are attached below.

Solution2:- Thermistor is a negative temperature coefficient device which means that its resistance decreases as the input value exceeds a threshold temperature limit, following which it allows the flow of current through it.In this scenario the threshold temperature is given as 25 deg.celsius or (298.15K). Further the output of the thermistor is causing the current to flow in the circuit which in turn allows the voltage sensor to generate a physical signal to control the switch operation. The controlled operation is based on the logic that the switch remains ON only for the duration t=10s to 30s, when the temperature is more than 25degree celsius. Next, when the switch in turned ON the DC motor gets the supply from the contolled voltage source and hence the cooling fan starts for the ON duration t=10s to 30s.

The following files have been attached to justify the above results.

1.Temperature scale of heater.

2. Graph showing switch operation & voltage sensor output.

3. parameters of fan (velocity and position variation).

4. Simulink model.