Week -2

Aim :

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

In the above arrangement, when the switch is closed the electromagnet receives electrical power from the battery and pulls the metal arm to hit the bell producing sound.

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

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

1) Doorbell

Theory:

When the door bell button is pressed, an electrical circuit is closed, which leads to the flowing of electric current through the electromagnet.The current then passes through the electromagnetic wire winding. A magnetic field is generated as a result, which is used to drive a sound making mechanism. Different types of sound making mechanisms are used to generate different sorts of noises.

Procedure :

• First the input is given with the help of pulse generator and its connected to electrical switch with the help of a simulink-ps converter and the input is observed by connecting scope.
• then the solver configuration block is connected to the switch.
• battery block is defined for volatge source.
• the battery is connected to an electrical switch and the switch is connected to the solenoid to complete the circuit.
• then we give the block for solenoid and connect it to an ideal translational motion sensor to measure the translation motion of the solenoid, the traslation motion of the bell is observed by connecting it to a scope with the help for ps-simulink converter.
• electrical reference and mechanical translation reference connected as earthing.
• stop time is given as 20 sec
• Initial position of the ideal translational motion sensor is given as 5.

parameters :

• pulse generator parameter :

• Solenoid mechanical parameters :

Simulink model :

output from scope :

2)Thermistor

Theory:

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.

Proceure :

• first we give the input signal with the help of repeating seqence stair block.
• the input signal block is connect to 's' port of the controlled temperature source block with the help of a simulink-ps converter.the 'B' port of the controlled temperature source is connected to the 'A' port(net heat flows through port A) of thermistor.
• a scope is connected to the input signal of observe the input.
• then we make a thermistor block and connect a battery to it as a voltage source.
• then we connect a resistor block and connect it to a voltage block in series to measure the voltage flowing through the resistor.
• display block is connected to "V"(v is the physical port that outputs the voltage value) of the voltage sensor with the help of a ps-simulink converter to display the output.
• a conditional switch block with 2 constant blocks of value '0' and '1' is connected to the "v" port of the voltage sensor.
• the threshold of the switch is calculated with the help of thermistor equation
• 8.29 ohms is calculated as the threshold at 25 degree celsius and it given as threshold for switch.
• T1 is the first temperature point in Kelvin
• T2 is the second temperature point in Kelvin
• R1 is the thermistors resistance at temperature T1 in Ohms
• R2 is the thermistors resistance at temperature T2 in Ohms
• the conditional switch block is connect to a scope to display the graph and the output of switch is connected to a lamp.the lamp glows red if the resistance across is less than the switch threshold meaning the fan if off, if the resistance across is higher than the switch threshold the lamp glows green meaning the fan is on.
• thermal reference and electrcal reference is connected to provide earthing.
• the initial stop time is given as 20 sec.

Simulink model :

The fan is off when the temperature is less than 25 degree celsius and the fan is on when the temp is greater than 25 degree celsius.

Input scope:

temperature below 25 degree celcius,fan is off

output scope :

0 in the graph indicates the fan is off.

temperature above 25 degree celcius, fan is on.

Output scope :

1 in the graph indicates fan is on

Parameters :

repeating sequence stair :

switch parameter: