Week -2

AIM:

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

Procedure:

Study 1

A solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix. The coil can be arranged to produce a uniform magnetic field in a volume of space when an electric current is passed through it.

A solenoid is a coil of wire designed to create a strong magnetic field inside the coil. By wrapping the same wire many times around a cylinder, the magnetic field due to the wires can become quite strong. The number of turns N refers to the number of loops the solenoid has. More loops will bring about a stronger magnetic field. The formula for the field inside the solenoid is;

B=μo. I.NL

where;

B= Magnetic field (N/Amp.m)

μo= Permeability of free space

I= Current (Amp)

N= Number of turns

L= Length (m)

Procedure:

1. An input signal is given according to given conditions (Amplitude = 1, Period = 4 sec, Pulse Width = 50%, Phase Delay = 2 sec).

2. A Simulink-PS Converter is used to convert the input Simulink signal into a physical signal.

3. A switch is connected to battery and solenoid respectively as shown. If the external physical signal PS is greater than the threshold, then the switch is closed, otherwise, the switch is open.

4. Solenoid converts electrical signals to mechanical signals.

5. The Ideal mechanical translational motion sensor converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity and position.

6. A PS-Simulink Converter is used to convert the physical signal into a Simulink output signal.

7. The Solver Configuration block specifies the solver parameters that your model needs before you can begin the simulation.

8. Finally, Scope and Display are used to obtain the output plot.

SIMULINK MODEL:

INPUT:

OUTPUT:

STUDY 2

A thermistor (or thermal resistor) is defined as a type of resistor whose electrical resistance varies with changes in temperature. Although all resistors’ resistance will fluctuate slightly with temperature, a thermistor is particularly sensitive to temperature changes.

There are two types of thermistors:

- Negative Temperature Coefficient (NTC) Thermistor

- Positive Temperature Coefficient (PTC) Thermistor.

In this study NTC type thermistor is used. This thermistor uses the B-parameter equation, where the resistance at temperature T is given by:

Where,

R0 = nominal resistance at the reference temperature

T0 = reference temperature

B = characteristic temperature constant

T = sensed temperature

The default values of R0, T0, and B in the thermistor block of Simulink are 1000 Ω, 298.15 K, and 3500 K, respectively.

SIMULINK MODEL:

PROCEDURE:

1. A signal builder is given according to given conditions (20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds

Fan conditions: ON if the temperature above 25 °C, OFF otherwise).

2. A Simulink-PS Converter is used to convert the input Simulink signal into a physical signal.

3. 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.

4. Thermistor is a resistor whose electrical resistance varies with changes in temperature.

5. A voltage source of 12V DC is given to the circuit.

6. A reference resistor is used to measure the fluctuations in the model.

Total Resistance in series;

RTotal= RThermistor+ RReference

7. A voltage sensor converts voltage measured between any electrical connections into a physical signal proportional to the voltage.

8. A PS-Simulink Converter is used to convert the physical signal into a Simulink output signal.

9. The threshold value obtained by the output of voltage sensor is used by the switch to display '1' and '0' using the if-else condition.

10. The Solver Configuration block specifies the solver parameters that your model needs before you can begin the simulation.

11. Finally, Scope is used to obtain the output plot.

INPUT:

OUTPUT: