Week -2

Aim: This challenge aims to make a Simulink model of a doorbell using a solenoid block and make
another Simulink model where a
thermistor will be used to sense the temperature of a heater & turn it on or turn it off the fan.

Objective:
1. Make a Simulink model of Doorbell using a so/eno7z/block with the following details:
in the above arrangement, when the switch is closed the electromagnet receives electrical power
from the battery and pulls the metal arm to hit the bell producing sound. Create a situation where
the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.
Assume remaining parameters.

2. Use a thermistor to sense the temperature of a heater & turn on or turn off the fan as per the
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 of Objective-1:
Theory:
oorbell
A doorbell is a signaling device typically placed near a door to a building's entrance. When a
visitor presses a button the bell rings inside the building, alerting the occupant to the presence
of the visitor. The heart of a doorbell is an electromagnet. Electromagnets are coils of wire
wrapped around a small piece of magnetic metal. When electricity passes through the wire, it
creates
a magnetic field around the wire. When you press a doorbell button, you complete an electrical
circuit thot allows
household electricity to flow through the doorbell's internal electromagnet. The magnetic field
generated by the electromagnet is then used to power a mechanism that creates the doorbell sound.
Doorbells ore low—voltage devices. This means they require relatively little energy to operate. An
important port of a
doorbell mechanism is the transformer. The transformer converts regular 120—volt household current
to the lower voltage (usually somewhere between 6—16 volts) required by the doorbell.
olenoid
A solenoid is a 3—dimensional structure of wire. When this wire is wrapped around a metallic block
in a coil and electricity is passed through it, it has some special magnetic properties.
Electromagnetic induction makes it on electromagnet that can be switched on or off. The side in
which the current appears to be passing clockwise is the South Pole, and the side in which the
current seems to be passing anticlockwise is the Northern Pole. The solenoid works just like a bar
magnet and therefore has many uses. This principle is used to create valves, among other things.
Where the solenoid operates an electric switch, it is a relay.

A simple diagram of doorbell

Simulink model of objective-1

The figure above is the representation of "A doorbell operated on solenoid". In this model, some
blocks are used to make the working model of the doorbell. These blocks are:

t.Pulse Generator: The Pulse Generator block generates square wave pulses at regular intervals. The
block waveform parameters, Amplitude, Pulse Width, Period, and Phase delay, determine the shape of
the output waveform.
2. Simulink-PS converter: Converts the unitless Simulink input signal to a Physical Signal.
3. Scope: Display signals generated during simulation.
4. SWitch: Switch controlled by an external physical signal.
5. Battery: The Battery block represents a simple battery model.
6. Solenold: Model electrical characteristics and generated force of solenoid.

7. Ideal Tronslotionol Motion Sensor: The Ideal Translational Motion Sensor block represents a
device that converts an across variable measured between two mechanical translationol nodes into a
control signal proportional to velocity or position. You con specify the initial position (offset)
as a block parameter. The sensor is ideal since it does not account for inertia, friction, delays,
energy consumption, and so on.
8. Mechanical Tronslotionol Reference: The Mechanical Translotional Reference block represents a
reference point, or frome, for all mechanical translational ports. All translational ports that are
rigidly clamped to the frame (ground) must be connected to a Mechanical Translotionol Reference
block.
9. Electrical Reference: The Electrical Reference block represents an electrical ground. Electrical
conserving ports of all the blocks that are directly connected to the ground must be connected to
on Electrical Reference block. A model with electrical elements must contain at least one
Electrical Reference block.
JO. Solver Configuration:The Solver Configuration block specifies the solver parameters that your
model needs before you can begin the simulation.
J7. PS-Simulink Converter: Convert physical signal into Simulink output signal.

Model Explanation:
1. The pulse generator is used to give the signal input where, Amplitude=1, Period=4 sec, Pulse
width= 50%, and Phase delay= 2 sec. (See Fig 4.)
2. After that, the input signal is converted into physical form with the use of "Simulink-PS
Converter" and further send to the switch of the electrical circuit.
3. The electrical circuit consists of a solenoid, a battery, and a switch. One end of the solenoid
is connected to the battery and its other end is connected to the switch. An electrical reference
is provided in the electrical circuit.
4. The mechanical part of the solenoid is connected to an ideal translation motion sensor and
mechanical translotionol reference.
5. The P-port of the sensor makes a connection with the "PS-Simulink Converter" to provide the
output in signal form. Further, the converter is connected with scope to display our output signal.
6. A solver configuration is connected to an electrical circuit to solve all parameters before the
beginning of the simulation.

Signal input in doorbell show below file.

Output:
Here we can see that the switch is closed for 2 seconds and after that switch is open. Amplitude= 0
means the switch is closed. It can also be seen that the plunger strikes after every 2 seconds.
The motion of the plunger was simulated and recorded and plotted in scope.

Output of doorbell model show below file.

Solution of Objective-2:
Theory:
A thermistor (or thermal resistor) is defined as a type of resistor whose electrical resistance
varies with temperature changes. Although all resistors' resistance will fluctuate slightly with
temperature, a thermistor is porticularly sensitive to temperature changes.
Thermistors oct as a passive component in a circuit. They ore an accurate, cheap, and robust way to
measure temperature. While thermistors do not work well in extremely hot or cold temperatures, they
are the sensor of choice for many different applications.

Simulink Model of Objective-2:

This figure shows the representation of thermistor connection which senses the temperature of a
heater and passes the signal to a switch where a threshold limit is already set. If the temperature
is above or equal to the threshold limit, then it gives "J" as output which is "Switch On". If the
temperature is below the threshold limit, then it will give "0" as output which means "Switch Off".
The input signal is generated with the help of a "Signal Builder" block (See Fig 9). This signal is
created according to the conditions given in this challenge. The conditions are as following:

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.
Here the temperature is converted in Kelvin from degree Celcius because the signal converter does
not take °C value as input. I also hove to set the signal unit as "Kelvin" in Simulink—PS
Converter.
The formula for conversion: 1 °C= 273.15 K

Size Signal I is:
From 0-10 sec- Temperature is 293.15 K From 10—30 sec— Temperature is 300.15 K From 30-50 sec-
Temperature is 296.15 K

Input signal creates on Signal Builder block show in below file.

Switch (Threshold limit is set here) show file.

Model Explanation:
1. At first, the signal is created in "Signal Builder" and further passes to "Simulink-PS
Converter" to convert the input signal into the physical signal.
2. This physical signal is connected to a block "Controlled Temperature Source". This block is
connected to the thermistor and a "Thermal reference" block.
3. The thermistor is a part of an electric circuit where a battery, a voltage sensor, a resistor
connected parallel to the voltage
sensor, an electrical reference are connected to make a complete circuit. A solver configuration is
connected to that electrical circuit to solve all parameters before the beginning of the
simulation.
5. From this port, we get our output and send it to two different "PS-Simulink Converter".
6. From converter-1, the signal is sent to the threshold switch. In the switch, the threshold limit
is set to 0.01189. If the temperature is above or equal to the threshold limit, then it gives
"1" as output which is "Switch On". If the temperature is below the threshold limit, then it will
give "0" as output which means "Switch Off". The input signal is generated with the help of
a "Signal Builder" block (See Fig 9}.
7. The switch is connected to the scope where we con see our output plot.
8. From converter-2, it converts the physical signal into a Simulink signal and sends the voltage
data from the Voltage Sensor to display. This display gives us the threshold value of voltage. This
value is set in the switch.

output:
It can be seen that the value of the signal is "0" from 0-10 sec because in this time the
temperature w means "Switch off the fan". After that, the signal value gives "1" as output from
10-30 sec because in this 27°C which is above 25°C means "Switch on the fan". The value of the
signal is again goes to "0" from 3 the temperature was 23°C which is below 25°C means "Switch off
the fan".
Now it is clear that our model is correct and fulfills all the input conditions.