Week -2

AIM: -

Make a Simulink model of doorbell using solenoid block and use a thermistor to sense the temperature of a heater & turn on or turn off the fan.

OBJECTIVE: -

Make a Simulink model of Doorbell using solenoid block with the following details; Create a situation where the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.

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 .

OBJECTIVE

• Doorbell: -

The most widely used form is the interrupter bell, which is a mechanical bell that produces a continuous sound when current is applied. The bell (B), which is often in the shape of a cup or half-sphere, is struck by a spring-loaded arm (A) with a metal ball at the end called a clapper, actuated by a solenoid (E). In its rest position the clapper is held away from the bell a short distance by its springy arm. When the switch (K) is closed, an electric current pass from the battery (U) through the winding of the solenoid. It creates a magnetic field thatattracts the iron arm of the clapper, pulling it over to give the bell a tap. This opens a pair of electric contact (T) attached to the clapper arm, interrupting the current to the solenoid. The magnetic field of the electromagnet collapses, and the clapper springs away from the bell. This closes the contacts again, allowing the current to flow to the solenoid again, so the magnet pulls the clapper over to strike the bell again. This cycle repeats rapidly, many times per second, resulting in a continuous ringing. The tone of the sound generated depends on the shape and size of the bell resonator. Where several bells are installed together, they may be given distinctive rings by using different size or shapes of bell, even though the strike mechanisms are identical. Another type, the single-stroke bell, has no interrupting contacts. The hammer strikes the gong once each time the circuit is closed.

• Solenoid: -

A solenoid is a device comprised of a coil of wire, housing and a moveable plunger (armature). When an electrical current is introduced, a magnetic field forms around the coil which draws the plunger in. More simply, a solenoid converts electrical energy into mechanical work. The coil is made of many turns of tightly wound copper wire. When an electrical current flows through this wire, a strong magnetic field/flux is created.

SIMULINK MODEL FOR DOOR BELL:-

Blocks used:

• Pulse generator: For generating a time interval to control the switch.
• 
• Simulink-PS converter: To convert Simulink system to physical system
• Battery: Is used for power supply
• SPST Switch: To control the flow of current through battery.
• Scope: To view the plots of Time interval, velocity and position of metal hammer.
• PS-Simulink converter: To convert physical system to Simulink system
• Electrical reference: To Grounding/Earthing the all electrical blocks
• Mechanical Translational reference: To grounding the all mechanical blocks
• Solver configuration: Defines solver settings to use for simulation.
• Solenoid block: To generate the electromagnetic to attracts the hammer.
• Ideal Translational motion sensor: device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity and position.
• Display block: To display the velocity and position values.

Procedure:

• In the pulse generator signals are generated for every 2 seconds to control the switch to ring the bell.
• According the signals the switch operates. When the switch is closed the electric power will flow through the solenoid and it creates EMF. This EMF creates the motion of hammer to hit the bell. By the ideal translational motion sensor, the velocity and position of the hammer will be known and recorded when PS-Simulink converter is added.

CONCLUSION: -

We can conclude from the above output results that we have successfully simulated doorbell mechanism operated by solenoid with given conditions as we can saw in above graph.

OBJECTIVE

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. 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. There are two types of thermistors:

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

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. This is the most common type of thermistor.

PTC thermistor the reverse relationship between temperature and resistance. When temperature increases, the resistance increases. And when temperature decreases, resistance decreases. Hence in a PTC thermistor.

SIMULINK MODEL FOR THERMISTOR:-

BLOCKS USED:

Signal Builder:-

The Signal Builder block allows you to create interchangeable groups of piecewise linear signal sources and use them in a model. You can quickly switch the signal groups into and out of a model to facilitate testing. In the Signal Builder window, create signals and define the output waveforms.

Simulink-PS Converter: -

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 Simscape physical network.

Controlled Temperature Source: -

The Controlled Temperature Source block represents an ideal source of thermal energy that is powerful enough to maintain specified temperature difference across the source regardless of the heat flow consumed by the system.

Thermal Reference: -

The Thermal Reference block represents a thermal reference point, that is, a point with an absolute zero temperature, with respect to which all the temperatures in the system are determined.

Thermistor: -

The Thermistor block represents an NTC thermistor which senses the temperature with respect to time.

Battery: -

The Battery block implements a generic dynamic model that represents the most popular types of rechargeable batteries.

Voltage Sensor: -

The Voltage Sensor block represents an ideal voltage sensor, that is, a device that converts voltage measured between two points of an electrical circuit into a physical signal proportional to the voltage.

Electrical Reference: -

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

Solver Configuration: -

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 PS-Simulink Convertor: -

The PS-Simulink Converter block converts a physical signal into a Simulink output signal. Use this block to connect outputs of a Simscape physical network to Simulink scopes or other Simulink blocks.

Switch: -

The Switch block passes through the first input or the third input signal based on the value of the second input. The first and third inputs are data input. The second input is control input. Specify the condition under which the block passes the first innut by using the Criteria for passing first and Threshold parameters.

Constant: -

The Constant block generates a real or complex constant value signal. Use this block to provide a constant signal input.

Display: -

The Display block shows the value of the output data. You can specify the frequency of the display. For numeric output data, you can also specify the format of display.

Scope: -

Display signals generated during simulation.in simple word display graph with respect to time.

In signal builder we created an input signal for system. As per given condition as follow

0 - 10 sec - temperature is 293.15 k (20°C)

10 - 30 sec - temperature is 300.15 k (27°C)

30 - 50 sec – temperature is 296.15 k (23°C)

Conclusion: -

We can conclude that from the above output results of our Simulink model for solenoid operated heaters give correct output and satisfy with all input conditions.

THANK YOU

SKILL LYNC