Week -2
AIM:
To determine a Simulink model of a doorbell using a solenoid block and make another Simulink model a thermistor will be used to sense the temperature of a heater & turn it on (or) off the fan.
OBJECTIVE:
1.Make a Simulink model of Doorbell using a solenoid bock with the given details:
In the above arrangement, when the switch is closed the electomagnet receives electrical powerr form the battery and pulls the metal arm to hit the bell producing sound. Create a situation where the switcch is closed for 2 seconds and then relased. Observe the physical movement of the plunger. Assume remaining parameters.
2.Use a thermistor to sense the temperature of a heater and turn ON and OFF the fan as per the below conditions:
Temperrature 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.
PART-1:
THEORY:
DOORBELL:
A door bell is a signaling device typically placed near a door to a buildings 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 electro magnet.
Electromagnets are coils of a wire wrapped around a small piece of magnetic metal. When electricity passes through the wire, it creates a magantic field areound the wire.
When you press a doorbell button you complete an electrical circuit that allows household electiricity to flow through the doorbells internal electomagnet is then used to power a mechanism that creates the doorbell sound.
Doorbells are low-voltage devices. This means they require relatively little energy to operate. An important part of a doorbell mechanism is the transformer. The transformer converts regular 120-volts household current to the lower voltage.
Usually from 6 to 16 volts is required by the door bell.
SOLENOID:
A solenoid is a 3-Dimensional structure of wire. When this wire is wrapped around a metalic block in a coil and electricity is passed through it. So it has some special magnetic properties. Electromagnetic induction makes it an electromagnetic that can be switched ON (or) OFF.
The side in which the current appears to be passing to be passing clockwise in the South pole and the side in which the current seems to be passing anti-clockwise is the North pole.The solenoid works just like a bar magnet and therfore has many uses.
The principle is used to create valves among other things. Where the solenoid operates an electirc switch it is a realy. The given below figure are example of doorbell with solenoid.
SIMULINK MODEL:
The figure below is the representation of a Doorbell operated on solenoid. In this model some blocks are used to make the working model of the doorbell.
1.Pulse Generator:
The Pulse Generator block generates square wave pulses at regular intervals. The block waveform parameters, Amplitude, Pulse Width, Period and phase delay and the shape of the output waveform.
2.Simulink-PS Converter:
This converts the unitless Simulink input signal to a Physical Signal.
3.Scope:
Display signals generated during simulation.
4.Switch:
Switch controls by an external physical signal.
5.Battery:
The battery block represents a simple battery model.
6.Solenoid:
Model electrical characterstics and generated a simple battery model.
7.Ideal Translational Motion Sensor:
This Ideal Translational Motion Sensor block represents a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velcoity (or) position.
We can specify the intial position as a block parameter. The sensor is ideal since it does not account for inertia, friction, delays, energy consumption.
8.Mechanical Translational Reference:
The Mechanical Translational Reference block represents a reference point or frame for all mechanical translational ports. All translational ports that are rigidly clamped to the frame must to be connected to a Mechanical Translational Reference block.
9.Electircal Reference:
The Electircal Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connceted to the ground must be conncected to an Electircal Reference block. A model with electrical elements must contains at least on Electircal Reference block.
10.Solver Configuration:
The Solver Configuration block specifies the solver parameters that our model needs before we can begin the simulation.
11.PS-Simulink Converter:
It convert physical signal into Simulink output signal.
MODEL EXPLANATION:
1.The pulse generator is used to give the signal input where, Amplitude=1, Period=4second, Pulse width=50% and the phase delay=2seconds.
2.After that, the input signal is converted into physical form with the help of Simulink-PS Converter and further send to the switch of the electrical circuit.
3.The electrical circuit consists of a solenoid, battery and a switch. One end of the solenoid is connected to the battery and its other end is connected to 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 translational reference.
5.The P-port of the sensor makes a connection with the PS-Simulink Converter to provide the output in signal form.
6.Further the converter is connected with scope to display our output signal.
7.A solver configuration is connected to an electrical circuit to solve all parameters before the begining of the simulation.
OUTPUTS:
1.PULSE GENERATOR:
2.Signal Input in doorbell:
3.OUTPUT OF DOORBELL MODEL:
Here we can see that the switch is closed for 2 seconds and after that switch is open. Amplitiude=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.
PART-2:
THEORY:
THERMISTOR:
A thermistor is defined as a type of resistor whose electrical resistance varies with temperature changes. Although all resistors will fluctuate slightly with temperature a thermistor is particularly sensitive to temperature changes.
It acts as a passive component in a circuit. They are an accurate cheap and robust way to measure temperature. While thermistors do not work well in extremely hot or cold temperatures they are the sensors of choice for many different applications. Types of thermistors are,
Simulink model :
The mentioned above figure represents of thermistor connection which senses the temperature of a heater and passes the signal to switch where a thersold limit is already set. If the temperature is above or equal to the thresold limit, then it gives 1as output which is SWITCH ON.
If the temperature is below the thersold limit then it will give 0as output which is SWITCH OFF. The input signal is generated with help of the Signal Builder block. This signal is created according to the conditions given in this challanges. The conditions are,
Temperrature 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 degrree Celcius because the signal converter does not take °C value as input. We also set the signal unit as Kelvin in Simulink-PS Converter.
The Signal-1 is:
From 0-10 sec - Temperature is 293.15K
From10-30sec - Temperature is 300.15K
From30-50sec - Temperature is 296.15K
1.Input Signal creates on signal builder block:
2.Switch(Thresold limit is assigned here):
MODEL EXPLANATION:
1.The signal is created in Signal Builder and it passes to Simulink-PS Converter to convert the input signal into the physical signal.
2.This signal is connected to a block Controlled Temperature Source. This block ic sonnected to the Thermistor and a Thermal Reference block.
3.The thermistor is a part of an electric circuit where a battery, voltage sensor, resistor is connected parallel to the voltage sensor. An electical reference are connected to make a complete circuit.
4.A solver configurations is connected to that electrical circuit to solve all parameters before the begining of the simulation.
5.The voltage sensors senses the temperature in the form of the voltage and send the data to its port V.
6.From the port we get output and and send it to two different PS-Simulink Converter.
7.From converter-1 The signal is sent to the threshold switch. In that the threshold limit is set to 1.1055e-02. If the temperatures is above (or) equal to the threshold limit then it gives 1 as output which is Switch ON.
8.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.
9.The switch is connected to scope where as we can see our output plot.
10.From Converter-2 it converts the physical signal into a Simulink signal and sends the voltage data from the voltage sensor to display.
11.This display gives the threshold value of voltage. This value is set in the switch.
OUTPUT:
The value of the signal is "0" from 0 to 10 sec because in this time the temperature was 20°C which is below 25°C means Switch OFF the fan. After that, the signal values gives 1 as output form 10-30sec because in this time the temperature was 27°C which is above 25°C means Switch ON the fan.
The values of the signal assign goes to "0" from 30-50 sec because in this time temperature was 23°C which is below 25°C means Switch OFF the fan.
RESULT:
Thus the Simulink model of a doorbell using a solenoid block and make another Simulink model a thermistor will be used to sense the temperature of a heater & turn it on (or) off the fan is completed sucessfully.
REFERENCES:
1.https://home.howstuffworks.com/home-improvement/repair/doorbell3.htm
2.https://circuitdigest.com/article/what-is-solenoid-its-working-principle-and-types
3.https://www.mathworks.com/help/physmod/sps/ref/thermistor.html