Simulink model of doorbell and implementation of thermistor

Aim of the experiment:

1. To make a Simulink model of doorbell using solenoid block.
2. To use a thermistor to sense the temperature of a heater and turn on or turn off the fan as per below conditions.

[Given Temperature conditions : 20 degrees from 0 to 10 seconds , 27 degrees from 10 to 30 seconds , 23 degree Celsius from 30 to 50 seconds]

[Given fan conditions : ON if the temperature above 25 degree Celsius , OFF otherwise]

Explanation:

STUDY-1 [DOORBELL]

The function of a doorbell button is to complete an electrical circuit that allows electricity to flow through the doorbells internal electromagnet. A magnetic field generated by the electromagnet is then used to create a sound.

WORKING PRINCIPLE OF DOORBELL BY USING SOLENOID

When the switch is pressed current flows through the circuit. The electromagnet is powered and generates a magnetic field that attracts the iron strip towards it striking the bell. When the striking arm strikes the bell, the contact is broken and the current stops flowing through the circuit. This causes the electromagnet to lose its magnetic field. The connected spring returns the striker to its original position. The contact is restored and the current flows through the circuit (Provided the main switch is pressed).

Simulink Model Of Doorbell :

Model Explanation :

A pulse generator is given as input with the following specifications. The condition was that the bell is rung for two seconds and then released. Same was implemented by given period as four seconds and pulse width as 50 % . Phase delay was given as two seconds , so the simulation starts from the switch. The signal from the pulse generator was converted using a Simulink – PS Converter and is given as input to the switch. A solenoid and battery is connected to it. The switch is also connected to the same circuit. Initial position was set to 5mm in translational sensor. Mechanical and electrical references were also connected. The output from the ideal translational motion sensor is converted using a PS-Simulink converter and is given to the scope for the results.

INPUT SIGNAL:

OUTPUT SIGNAL:

RESULTS: The simulation was run for 30 seconds and the output obtained is shown above . It can be observed that , at each 2 seconds interval the bell is ringing.

STUDY-2[THERMISTOR]

A Thermistor is a type of resistor whose electrical resistance varies with changes in temperature.

WORKING PRINCIPLE OF THERMISTOR

A signal generator is given according to the given conditions :

(20 degree celsius from 0 to 10 seconds, 27 degree Celsius from 10 to 30 seconds , 23 degree Celsius from 30 to 50 seconds )

Fan conditions (ON if the temperature is above 25 degree Celsius and OFF otherwise)

Simulink Model Of Thermistor:

Model Explanation:

A simulink–PS converter is used to convert the input Simulink signal into a physical signal. A controlled temperature source is an ideal energy source in a thermal network that can maintain a controlled temperature difference regardless of the heat flow rate. A voltage source of 12 volt DC is given to the circuit. In addition a reference resistor is used to measure the fluctuations. A voltage sensor converts voltage measured between any electrical connections into a physical signal after that a PS-Simulink converter is used to convert the physical signal to a Simulink signal. The value obtained by the voltage sensor is used by the switch to display 1 and 0 using If Else condition. A solver configuration block is used to specify the solver parameters for the model.

INPUT SIGNAL:

(Generated Input Signal)

 OUPUT SIGNAL:

(Angular Velocity)

 

RESULTS: The above model is run for temperature sensing and operating the fan according to the given conditions. For the first and last 20 seconds the fan is OFF as the temperature is less than 25 degree Celsius and for 20 to 30 seconds , the fan is ON as the temperature is greater than 25 degrees Celsius.

CONCLUSION:

Hence , The given problem was simulated according to given conditions :

1-The physical movement of the plunger was observed while simulating the doorbell model.

2-The fan temperature was sensed by the thermistor in the heater model. For the first and last 20 seconds the fan is OFF and for the next 20-30 seconds the fan is ON because the temperature is greater than 25 degree celsius .