Week -2

1) Answer:

SOLENOID:

A solenoid is a type of electromagnet, the purpose of which is to generate a control 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. The term solenoid was coined in 1823 by Ander-Marie Ampere to designate a helical coil. In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid value, an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic value, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch for example, an automobile starter solenoid or linear solenoid. Solenoid bolts, a type of electromechanical locking mechanism also exist. In electromagnetic technology, a solenoid is an actuator assembly with a sliding ferromagnetic plunger inside the coil. Without power, the plunger extends for part of its length outside the coil; applying power pulls the plunger into the coil. Electromagnetic with fixed core are not considered solenoid.

OBJECTIVES :-

FOR DOOR BELL :

Create a situation where the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.

SIMULINK MODEL:

DOOR BELL:

EXPLANATION:

From the above governing circuit of a door bell, we know that we need a switch, solenoid, battery and a plunger.

So, in order to get all these components into a Simulink model we have to taken block that perform same action what the above devices performs

Now first a ‘Solenoid Block’ is taken to respect a solenoid in the model, then to represent the battery we have to taken Battery Block from the library browser.

Then this ‘Solenoid Block’ and ‘Battery Block’ are connected to each other via positive and negative terminals.

A ‘Switch Block’ is placed in between ‘Solenoid Block’ and ‘Battery Block’ and it is connected with both the blocks.

Now for the switch to operate we need to provide a physical signal through ‘PS’ port in the ‘Switch Bock’. The provide physical signal should be greater than the threshold of the switch, for switch being closed, or else it will open.

Now this whole battery, switch and solenoid path is connected to an ‘Electrical Reference Block’ which represents earthing of the circuit. This ‘Electrical Reference Block’ should be connected with negative port of the ‘Battery Block’.

Then in the ‘Solenoid Block’, ‘R’ and ‘C’ are to variable which represent plunger and fixed point respectively.

Now this ‘R’ is connected to a ‘R’ of ‘Ideal Translation Motion Sensor Block’, witch senses the positive of the plunger in the ‘Solenoid Block’ and gives the output.

Now the ‘Ideal Translation Motion Sensor Block’ the output given as ‘V’ and ‘P’ which represents the velocity and position of plunger. Since we are only interested in knowing changing position of the plunger, so we need only result from ‘P’ output.

Now ‘C’ in the ‘Ideal Translation Motion Sensor Block’ is a mechanical translation conserving port, which means that mechanical process starts from ‘R’ and ends at ‘C’ and again it starts at ‘R’ and the cycle goes on.

So ‘C’ in the ‘Ideal Translation Motion Sensor Block’ is connected to a ‘Mechanical Translation Reference’ which respect a fixed point where is the rigidly clamped in real time.

Similarly ‘C’ of ‘Solenoid Block’ is also connected to the same ‘Mechanical Translation Reference’ as fixed point for the solenoid.

Since we position to the plunger as output from ‘Ideal Translation Motion Sensor Block’ we have connected port ‘P’ to a ‘PS- Simulink converter’ where the physical value from port ‘P’ are converted into Simulink value for port ‘P’ as converted into Simulink value, and then this ‘PS-Simulink converter’ is connected to ‘Scope Block’ which will generated a graph for change in position for plunger from port ‘P’ for ‘Ideal Translation Motion Sensor Block’.

Now to provide physical signal for operating the switch, we have use a ‘Pulse Generator Block’, which generates a continuous square pulse.

GRAPHS:

Figure 1

Figure 2:

2) Answer :

Thermistor:

A thermistor is a type of resistor whose resistance is depending on temperature, more so then in standard resistors. The world is combination of thermal resistor. Thermistors are widely used as inrush current limiters, temperature sensors negative temperature coefficient or NTC type typically, self regulating heating element positive temperature coefficient or PTC type typically.

Thermistors are of two opposite fundamental types:

With NTC thermistors, resistance decreases as temperature rises. An NTC is commonly used as a temperature sensor, or in series with a circuit as an inrush current limiter.

With PTC thermistors, resistance increases as temperature raises. PTC thermistors are commonly installed in series with a circuit. And us to protect against overcurrent conditions, as resettable fuses.

Thermistor are generally produced using powdered metal oxide. With vastly improved formulas and techniques over the past 20 years, NTC thermistor can now achieve accuracies over wide temperature ranges.

Thermistor differ from resistance temperature detectors in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response in also different RTDs are useful over larger temperature ranges, while thermistor typically achieve a greater precision within a limited temperature range.

Blocks used in model:

• Signal builder
• Controlled Temperature Source
• Thermistor
• Resistor
• Voltage Sensor
• Battery
• Switch
• Scope
• Simulink – PS Converter
• PS – Simulink Converter
• Solver Configuration
• Electrical Reference

Given inputs:

At Point1 – Time 0 sec –

Temperature – 293k,

At Point2 – Time 10 sec –

Temperature – 293k,

At Point3 – Time 10 sec –

Temperature – 300k,

At Point4 – Time 30 sec –

Temperature – 300k,

At Point5 – Time 30 sec –

Temperature – 296k,

At Point6 – Time 50 sec –

Temperature – 296k,

Simulink Model :

OUTPUT:

CONCLUSION:

1. Thus, both the objectives were achieved successfully.

2. Similar approach can be used for simulating other physical devices using simulink.