Week -2

                                         WEEK-2 CHALLENGE 

1. Make a Simulink model of Doorbell using solenoid block with the following details:

How does the doorbell work?

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 that 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.

Solenoid Working Principle

 The solenoid simply works on the principle of “electromagnetism”. When the current flow through the coil magnetic field is generated in it, if you place a metal core inside the coil the magnetic lines of flux is concentrated on the core, which increases the induction of the coil as compared to the air core.

The above image shows the diagram of electronic doorbell when the switch is closed the circuit becomes active and Solenoid activates the plunger it will hit the bell and produces sounds

The following Simulink blocks are required for DOORBELL

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.

The Simulink-PS Converter block converts the input Simulink signal into a physical signal. Use this block to connect Simulink sources or other Simulink blocks to the inputs of a Physical Network diagram.

Solenoid block required to produce the electromagnetic to attract the hammer.

Battery it is used as power source

SPST Switch is used to control the flow of electric current from the battery

The 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 velocity or position. You can specify the initial position (offset) as a block parameter.

The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connected to ground must be connected to an Electrical Reference block. A model with electrical elements must contain at least one Electrical Reference block.

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 (ground) must be connected to a Mechanical Translational Reference block.

SCOPE is used to view results

Each physical network represented by a connected Simscape block diagram requires solver settings information for simulation. The Solver Configuration block specifies the solver parameters that your model needs before you can begin simulation.

The following Simulink blocks are required for DOORBELL

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.

The Simulink-PS Converter block converts the input Simulink signal into a physical signal. Use this block to connect Simulink sources or other Simulink blocks to the inputs of a Physical Network diagram.

Solenoid block required to produce the electromagnetic to attract the hammer.

Battery it is used as power source

SPST Switch is used to control the flow of electric current from the battery

The 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 velocity or position. You can specify the initial position (offset) as a block parameter.

The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connected to ground must be connected to an Electrical Reference block. A model with electrical elements must contain at least one Electrical Reference block.

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 (ground) must be connected to a Mechanical Translational Reference block.

SCOPE is used to view results

Each physical network represented by a connected Simscape block diagram requires solver settings information for simulation. The Solver Configuration block specifies the solver parameters that your model needs before you can begin simulation.

The following Simulink blocks are required for DOORBELL

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.

The Simulink-PS Converter block converts the input Simulink signal into a physical signal. Use this block to connect Simulink sources or other Simulink blocks to the inputs of a Physical Network diagram.

Solenoid block required to produce the electromagnetic to attract the hammer.

Battery it is used as power source

SPST Switch is used to control the flow of electric current from the battery

The 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 velocity or position. You can specify the initial position (offset) as a block parameter.

The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connected to ground must be connected to an Electrical Reference block. A model with electrical elements must contain at least one Electrical Reference block.

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 (ground) must be connected to a Mechanical Translational Reference block.

SCOPE is used to view results

Each physical network represented by a connected Simscape block diagram requires solver settings information for simulation. The Solver Configuration block specifies the solver parameters that your model needs before you can begin simulation.

     BLOCK DIAGRAM OF SIMULINK DOORBELL:

PROCEDURE:-

Pulse generator block with Amplitude = 4, time for 4 seconds, pulse width 50% and phase delay = 2 secs it is given to Switch through Simulink-PS converter this converter converts normal signal to physical signal input for duration of 4 sec in which 2sec is in ON Position and 2 sec in OFF position  

When Electricity reaches solenoid from battery source it operates for 2 seconds as we provided the input signal

Here for the battery source or electrical circuits in Simulink we should connect a electrical reference block

The operation of solenoid can be seen in ideal translational motion sensor here the physical output is converted into normal signal output with the help of PS-Simulink converter

For the mechanical system, a solver configuration has to be connected and for the mechanical circuit a mechanical translational circuit has to be connected

When we run simulation for 10 seconds

INPUT SIGNAL

OUTPUT SIGNAL

VELOCITY:

CONCLUSION:

From above observation we can see that oscillation are produced at 2, 4, 6 & 8 seconds and rung for every 2 seconds 

2. Use a thermistor to sense the temperature of a heater & 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

What is a 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.

Thermistors act 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 sensor of choice for many different applications.

How Does a Thermistor Work

The working principle of a thermistor is that its resistance is dependent on its temperature. We can measure the resistance of a thermistor using an ohmmeter.

If we know the exact relationship between how changes in the temperature will affect the resistance of the thermistor – then by measuring the thermistor’s resistance we can derive its temperature.

How much the resistance changes depends on the type of material used in the thermistor. The relationship between a thermistor’s temperature and resistance is non-linear. A typical thermistor graph is shown below:

If we had a thermistor with the above temperature graph, we could simply line up the resistance measured by the ohmmeter with the temperature indicated on the graph.

By drawing a horizontal line across from the resistance on the y-axis, and drawing a vertical line down from where this horizontal line intersects with the graph, we can hence derive the temperature of the thermistor.

Thermistor Types

There are two types of thermistors:

• Negative Temperature Coefficient (NTC) Thermistor
• Positive Temperature Coefficient (PTC) Thermistor

NTC Thermistor

In an NTC thermistor, when the temperature increases, resistance decreases. And when temperature decreases, resistance increases. Hence in an NTC thermistor temperature and resistance are inversely proportional. These are the most common type of themistor.

PTC Thermistor

A PTC thermistor has the reverse relationship between temperature and resistance. When temperature increases, the resistance increases.

And when temperature decreases, resistance decreases. Hence in a PTC thermistor temperature and resistance are inversely proportional.

Although PTC thermistors are not as common as NTC thermistors, they are frequently used as a form of circuit protection. Similar to the function of fuses, PTC thermistors can act as current-limiting device.

When current passes through a device it will cause a small amount of resistive heating. If the current is large enough to generate more heat than the device can lose to its surroundings then the device heats up.

In a PTC thermistor, this heating up will also cause its resistance will increase. This creates a self-reinforcing effect that drives the resistance upwards, therefore limiting the current. In this way, it acts as a current limiting device – protecting the circuit.

FOLLOWING SIMULINK BLOCKS REQUIRED TO BUILD A THERMISTOR MODEL TO SENSE THE TEMPERATURE OF A HEATER TURN ON & OFF THE FAN AS PER BELOW CONDITIONS:

SIGNAL BUILDER

CONTROLLED TEMPERATURE SOURCE

THERMISTER

RESISTOR : 10 OHMS

CURRET SOURCE: 10 AMPS

CURRENT SENSOR

ELECRTRICAL REFERENCE

SOLVER CONFIGURATION

CONSTANT BLOCKS

SWITCH: 9.909 THRESHOLD

CONTROLLED VOLTAGE SOURCE

DC MOTOR

IDEAL ROTATOINAL MOTION SENSOR

DISPLAY

SCOPE

SIMULINK MODEL OF FAN CONTROLLED THERMISTOR

PROCEDURE:

SIGNAL BUILDER block is used to generate input signal i.e. the parameter 20°C (293K) from 0 to10 seconds, 27°C (300K) from 10 to 30 seconds and 23°C (296K) from 30 to 50 seconds.

The signal from signal builder block is given to thermistor through Simulink to PS converter

Here when the temperature changes in thermister the value of resistance also changes due to this the value of current also changes in thermister. the current 10 Amps is supplied from the current source to both thermister and resistor

Through current sensor the threshold voltage is calculated in order to ON FAN at 25°C switch requires threshold is 9.909 the switch input is 0 or 1 is converted into physical signal through Simulink to PS converter the switch output is given to controlled voltage source DC motor which acts as FAN

Through this threshold value the switch is used to control the fan/dc motor by using ideal rotational motion sensor the angular velocity and displacement values are also caluclated

INPUT

OUTPUT

CONCLUSION:

During the temperature 293 (20°C) kelvin and 296 (23°C) kelvin the fan rotates at a speed of 1454 RPM as shown in output plot and at 300 kelvin (27°C) the FAN speed is reduced to 0 RPM