Week -2

Ans-1

Simulink model of doorbell using solenoid block-

Solenoid- When conductor is turned into helical shpe in such a way that magnetic field of every turn is to be in same direction, then a strong magnetic field is stablished by a device called solenoid. It may be air cored or may be iron cored.

Doorbell- It is a ringing machine, produced sound when someone push the switch. It is used for knocking purpose. it's working is based on magnetic attraction effect. When switch is closed a strong magnetic field setup by solenoid, which attracts the magnetic material pulled on the plunger-head. Then plunger hits on the bell device and create a sound. In this duration circuit contact is opened and due to effect of spring plunger comes on original position.

Here Simulink model is shown below-

Block used-

Pulse generator- It generate the pulse signal according to parameters setting. Here, amplitude is 1, having period of 4sec with 50% of pulse width taking as 1sec phase delay is provided.

Simulink- PS converter- It converts the simulink signal into physical system signal.

Switch- As desired time is given that switch is closed for 2sec put a threshold value here to fullfil the condition.

Battery- A battery is also connected to fed required input power to solenoid, with negative port is grounded.

Solenoid- This block uses for two purpose as to setup magnetic field and to generate machanical stroke (X1,X2)=[0,5]mm with 7.5N force.

Translational motion sensor- It sense the motion between two nodes and produces output physical signal as position and velocity.

PS- Simulink converter- The physical signal of position is converted in simulink signal to observe in scope and display using this block.

Scope and Display- It is output block useful for observation of reading.

Solver configuration- This block defines the solver parameter needs for simulation.

Result-

As the graph shows 1sec delay is given and then switch is closed for 2sec (desired) plunger strikes and after 2sec switch opend and plunger comes into initial position. It repeates two times because simulation runs for 8sec.

Conclusion-

The doorbell simulation model using solenoid block is simulated and obsedved the output data as desired.

Ans-2

Thermistor to sense the temperature of a heater & turn on or turn off the fan-

Thermister- As name suggest, the working of thermistor is based on relation between temperature and resistance. Actually it measures resistance but it depends on change in temperature. The relation between resistance and temperature changes material to material. It uses in measure the oil and coolent temperature in car and also uses in household applications.

Blocks used-

Signal builder- This block is used to generate the signal as desired, here desired temperature signal is shown-

For 0 - 10sec Produce 20°C i.e. = 293K

For 10 - 30sec Produce 27°C i.e. = 300K

For 30 - 50sec Produce 23°C i.e. = 296K

Simulink- PS converter- It converts the simulink signal to physical signal, here first order input filtering is selected.

Controlled temperature source- It is a thermal energy source which gives the output as the difference temperature between port S to port A. Port A is thermally grounded.

Thermistor- This block represent a negative temperature coefficient (NTC) type thermistor.

Voltage sensor- This block senses the voltage and converts proportionly to physical signal.

PS- Simulink converter- Using this block physical signal is converted into simulink signal for further measurement.

Switch- It is a two port switch passes input 1 if U2> Threshold

Pass input 3 if U2<= Threshold

Here we set the threshold value is 0.01189 as it is the physical signal value at 25°C temperature.

Result-

The output graph is shown below-

0 indicates OFF the fan

1 indicates ON the fan

At 25°C i.e. 298K the simulink output value comes 0.01189 which set as threshold value for switch that means above 25°C output comes 1 i.e. switch ON the fan and below or equal to 25°C output comes to 0 i.e switch OFF the fan.

Conclusion-

For sensing the heater temperature thermistor is used and succesfully obtained to desired condition to turn ON/OFF the fan.