Week -2

Aim:

1)Make a Simulink model of Doorbell using solenoid block. 

2)Use a thermistor to sense the temperature of a heater & turn on or turn off the fan.

Solenoid:

A solenoid  is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field. The coil can 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 André-Marie Ampère

The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis; for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape (not unlike an arc spring).

Solenoids provide magnetic focusing of electrons in vacuums, notably in television camera tubes such as vidicons and image orthicons. Electrons take helical paths within the magnetic field. These solenoids, focus coils, surround nearly the whole length of the tube.

In engineering, the term "solenoid" refers not only to the electromagnet but to a complete apparatus providing an actuator that converts electrical energy to mechanical energy.

Thermistor:

A thermistor is a resistance thermometer, or a resistor whose resistance is dependent on temperature. The term is a combination of “thermal” and “resistor”. It is made of metallic oxides, pressed into a bead, disk, or cylindrical shape and then encapsulated with an impermeable material such as epoxy or glass.

There are two types of thermistors: Negative Temperature Coefficient (NTC) and Positive Temperature Coefficient (PTC). With an NTC thermistor, when the temperature increases, resistance decreases. Conversely, when temperature decreases, resistance increases. This type of thermistor is used the most.

A PTC thermistor works a little differently. When temperature increases, the resistance increases, and when temperature decreases, resistance decreases. This type of thermistor is generally used as a fuse.

Typically, a thermistor achieves high precision within a limited temperature range of about 50ºC around the target temperature. This range is dependent on the base resistance.

The thermistor symbols are:

 Thermistor Symbol — US and Japan

The arrow by the T signifies that the resistance is variable based on temperature. The direction of the arrow or bar is not significant.

Thermistors are easy to use, inexpensive, sturdy, and respond predictably to changes in temperature. While they do not work well with excessively hot or cold temperatures, they are the sensor of choice for applications that measure temperature at a desired base point. They are ideal when very precise temperatures are required.

Some of the most common uses of thermistors are in digital thermometers, in cars to measure oil and coolant temperatures, and in household appliances such as ovens and refrigerators, but they are also found in almost any application that requires heating or cooling protection circuits for safe operation. For more sophisticated applications, such as laser stabilization detectors, optical blocks, and charge coupled devices, the thermistor is built in. For example, a 10 kΩ thermistor is the standard that is built into laser packages.

Governing diagrams:

Basic components used to generate a simple doorbell circuit are:

1.Battery

2.Switch

3.Solenoid

4.A bell with Plunger

For thermistor:

Basic components used to generate a simple cooling fan circuit are:

1.Battery

2.Thermistor

3.Fan

4.Transistor

5.Resistor

Objectives:

For door bell:

1)Create a situatioin where the switch is closed for 2 seconds and then released.observe the physical movement of the plunger.

For Fan

1)Temperature source should be 20degreeC from 0 to 10 seconds,27 degree C from 10 to 30 seconds,23 degreeC from 30 to 50 seconds.fan conditions should be ON if the temperature above 25 degree ,Off otherwise

Simulink Model:

Door bell:

Explanation:

1)The electrical input block Inclues switch,grounding,Simulink to PS converter

2)The solenoid is Electromechanical devices which takes inputs from electrical model and converts into mechanical output

3)The mechanical blocks consists of Motion sensor,PS to simulink convert ,Scope and a solver

4)The pulse generator is also connected to Electrical input block and the parameters are given as below

Outputs:

2)For Fan operations using Thermistor:-

 Explanation:

1)To create a simple cooling fan model using thermistor we need a thermistor,battery ,resistor,voltmeter ,a logical switch which are the basix components of the circuit we need the simulink mode

2)The thermistor is connected to a battery & resistor block along with grounding

3)Voltage sensor is connected parallel to resistor block to measure voltage across component

4)In order to provide different temperatures to fan we need to provide controlled temperature source block which only gives a specified temperature as output even though heat flow is more

5)to send signals we have to use signal builder block 

Outputs:

 we obtain different plots when the temperature varies as shown below