Week -2

AIM:

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

2.  Use a thermistor to sense the temperature of a heater & turn on or turn off the fan as per below conditions.

DOORBELL USING SOLENOID:

The Solenoid is a electromagnet. On passing current through the conducting wires a magnetic field is generated around it which attracts magnetic materials. This phenomenon is used in the bell. When the switch of the bell is pressed the current passes through the circuit, exciting the electromagnet and pulling the plunger towards the metal portion. This produces a ringing sound.

Blocks used in model:

• Pulse Generator
• Switch
• Battery
• Solenoid
• Ideal Translational Motion Sensor
• Mechanical Translational Reference
• Electrical Reference
• Scope

. Pulse Generator:-

 Light pulse generators are the optical equivalent to electrical pulse generators with rep rate, delay, width and amplitude   control. The   output in this case is light typically from a LED or laser diode.

. BATTERY:-

 Battery is a device consisting of one or more electrochemical cells with external connections^[1] for powering electrical devices such   as flashlights, mobile phones, and electric cars

.SOLENIOID:-

Solenioid a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed heli

SIMULINK MODEL:-

Note that the circuit is made up of subcircuits blue circuit and green circuit.

Simulink automatically allocates blue color to any electrical circuit. Here we have a battery, solenoid, and a switch connected to a pulse generator present in the circuit.

INPUT SINGAL SIMULINK MODEL

OUTPUT SINGAL SIMULINK MODEL:-

PART - 2:-

OBJECTIVE:-

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.

INTODUCTION:-

A thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word is a combination of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors (negative temperature coefficient or NTC type typically), self-resetting overcurrent protectors, and self-regulating heating elements (positive temperature coefficient or PTC type typically).

USES THERMISTOR:-

A thermistor is a specific type of resistor that uses sensors to help regulate cold and heat. They can do more then simply regulate temperature. They are also used for voltage regulation, volume control, time delays, and circuit protection. These products are made up of ceramic and metal oxides, but it also contains circuits and wires

Thermistor:-

OUTPUT RESULT:-

The requirement is such that, the fan should be turned on when the temperature sensed is greater than 25 degree celsius. To fullfill this objective we use a voltmeter to find the voltage of the circuit at different temperatures. It is found that, voltage at 25 degree celsius is approximately 0.23 V. Now, this voltage signal is passed through a switch. The switch is configured in such a way that, it is open if the voltage across the voltmeter is less than 0.23 V (temperature less than 25 degree celsius) and close if the voltage across the voltmeter is greater than 0.23 V (temperature more than 30 degree celsius). The threshold of the switch is set to 0.23 V.

 From the switch output we can see that, only output is between 10-30 seconds as the temperature is greater than 25   degree celsius.   So,  this output can be given to Fan for the simulation.