Challenge

Simulink model of doorbell

GGannoji Srikanth Chary2 Sept 2020

Aim:

To make a Simulink model of doorbell using solenoid block.
To create a Simulink model of thermistor to sense the temperature of a heater.

Software used:

MATLAB R2020a_SIMULINK

Theory:

In the electric bell when the switch is closed the electromagnet receives the electric power from battery and pulls the metal hammer to hit the bell producing sound.

Created a model of Doorbell for switch is closed for 2 sec and release.

Blocks used:

Pulse generator: For generating a time interval to control the switch
Simulink-PS converter: To convert Simulink system to physical system
Battery: Is used for power supply
SPST Switch: To control the flow of current through battery.
Scope: To view the plots of Time interval, velocity and position of metal hammer.
PS-Simulink converter: To convert physical system to Simulink system
Electrical reference: To Grounding/Earthing the all electrical blocks
Mechanical Translational reference: To grounding the all mechanical blocks
Solver configuration: Defines solver settings to use for simulation.
Solenoid block: To generate the electromagnetic to attracts the hammer.
Ideal Translational motion sensor: device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity and position.
Display block: To display the velocity and position values.

Procedure:

In the pulse generator signals are generated for every 2 seconds to control the switch to ring the bell.
According the signals the switch operates. When the switch is closed the electric power will flow through the solenoid and it creates EMF.
This EMF creates the motion of hammer to hit the bell. By the ideal translational motion sensor, the velocity and position of the hammer will be known and recorded when PS-Simulink converter is added.

Output:

Time vs Amplitude plot

2. Time vs velocity plot

3. Time vs position plot

Bell is rung for every 2 sec in the span of 10 sec.

Thermistor:

Thermistors are temperature-dependent resistors, changing resistance with changes in temperature. They are very sensitive and react to very small changes in temperature. They are best used when a specific temperature needs to be maintained, and when monitoring temperatures within 50⁰C of ambient.

Thermistors, as a part of a temperature control system are the best way to measure and control heating and cooling of a Peltier device. Their ability to adjust in minute increments allow the greatest overall system stability. Thermistors can be embedded in a surface-mounted on the device needing temperature monitoring. Depending on type, they can measure fluids or solids. They are made up of metallic oxides.

Input Temperatures:

T= 20⁰C from 0 to 10 sec

T= 27⁰C from 10 to 30 sec

T= 23⁰C from 30 to 50 sec

Fan condition is:

ON if T > 25⁰C

else OFF

Blocks used:

Thermistor: This block represents an NTC thermistor using the B-parameter equation. The resistance at temperature T is given by R(T) = R0*exp(B*(1/T-1/T0)) where R0 is the Nominal resistance at the reference temperature T0, and B is the Characteristic temperature constant. The temperature T of the thermistor is governed by the equation m*c*dT/dt = Q where Q is the net heat flow into port A, m is the mass and c is the lumped specific heat capacity. The thermal mass m*c is calculated from the Thermal time constant t_c and the Dissipation factor K_d using the equation m*c = K_d*t_c.
Resister: The voltage-current (V-I) relationship for a linear resistor is V=I*R, where R is the constant resistance in ohms.
Signal builder: To build the input Temperature signals
Scope: Used for plotting
Simulink-PS converter: Converts the Simulink input signal to a Physical Signal.
Controlled Temperature source: This block represents an ideal energy source in a thermal network that can maintain a controlled temperature difference regardless of the heat flow rate. The temperature difference is set by the physical signal port S. A positive temperature difference causes the temperature at port B to be greater than the temperature at port A.
Temperature sensor: To sense the temperature. This block measures temperature in a thermal network. There is no heat flow through the sensor. The physical signal port T reports the temperature difference across the sensor. The measurement is positive when the temperature at port A is greater than the temperature at port B.
Thermal reference: To grounding the thermal network
Electrical reference: To grounding the electrical network
Mechanical rotational reference: To ground the mechanical rotational parts
Slover configuration: Defines solver settings to use for simulation.
Battery: Power source
Voltage sensor: To sense the threshold voltage.
Switch: condition switch to control based on threshold value.
Controlled voltage source: To regulate the voltage.
DC motor: Used as a rotating device
Ideal rotational motion sensor: To sense the angular velocity and angular displacement of a DC motor.

Flow process:

We need to define the inputs required in signal builder to provide the signal to thermistor through controlled temperature source. Simulink-PS converter is used to convert the signals to physical system.
Through voltage sensor the threshold voltage is calculated. Through this threshold value the switch operates to control the fan/DC motor. By using the ideal rotational motion sensor, the angular velocity and displacement values were calculated and recorded by using PS-Simulink converter in display and scope.

Output: