Doorbell and Heater model using SIMULINK
AIM: To simulate a doorbell and heater model using Simulink.
OBJECTIVE:
1. To observe the physical movement of the plunger by creating a situation where the switch is closed for 2 seconds and then released.
2. To use a thermistor to sense the temperature of a heater and turn on or turn off the fan as per below conditions:
Temperature source: 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
SOLUTION:
Part #1:
THEORY:
Doorbell: The electric doorbell is a simple circuit that triggers a sound on the completion of the circuit by pressing the button.
When the switch is pressed, the circuit loop is complete which causes the current to flow through the circuit. The arm which strikes the gong is connected to spring at one end and an iron ball at the other end. This is called a hammer or a striker. The arm is attached to an iron strip which is attracted to the electromagnet when the circuit is complete and the current flowing through it.
Solenoid: 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 = frac{mu_o . I .N} L`
where;
`B` = Magnetic field (N/Amp.m)
`mu_o` = Permeability of free space
`I` = Current (Amp)
`N` = Number of turns
`L` = Length (m)
Procedure/Steps:
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.
A Simulink model for the plunger movement according to given conditions is shown below.
Input #1:
Output #1:
A plot for m = 0.1 kg is displayed below.
A plot for m = 0.01 kg is displayed below. We can observe less fluctuation as compared to the previous plot.
Part #2:
THEORY:
Thermistor: 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
Procedure/Steps:
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;
`R_{Total} = R_{Thermis t o r} + R_{Reference}`
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.
A Simulink model for temperature sensing and operating the fan according to given conditions are shown below.
Input #2:
A plot is displayed below for: 20 °C (293 K) from 0 to 10 seconds, 27 °C (300 K) from 10 to 30 seconds, 23 °C (296 K) from 30 to 50 seconds.
A plot for the voltage sensor is displayed below.
Output #2: For the first and last 20 sec, the fan is OFF as temperature is less than 25 °C and for 20-30 sec, the fan is ON as temperature is greater than 25 °C.
CONCLUSION: Hence, the given problem was simulated according to the given conditions:
- The physical movement of the plunger was observed in the Doorbell model.
- Fan temperature was sensed by the thermistor in the Heater model.
REFERENCES:
1. Door Bell
2. Solenoid
3. Thermistor