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.
• Assume remaining parameters.

2. 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

AIM#1

Make a Simulink model of Doorbell using solenoid block.

THEORY :

DOORBELL : When you press a doorbell button, you complete an electrical circuit that allows household electricity to flow through the doorbell's internal electromagnet. The magnetic field generated by the electromagnet is then used to power a mechanism that creates the doorbell sound. Doorbells are low-voltage devices.

SOLENOID : A solenoid is a three dimensional structure of wire. When this wire is wrapped around a metallic block in a coil and electricity is passed through it, it has some special magnetic properties. Electromagnetic induction makes it an electromagnet that can be switched on or off. The side in which the current appears to be passing clockwise, is the South Pole, and the side in which the current seems to be passing anticlockwise is the Northern Pole. The solenoid works just like a bar magnet, and therefore has many uses.

WORKING PRINCIPLE OF DOORBELL BY USING SOLENOID:

• The switch is pressed and current flows through the circuit.

• The electromagnet is powered and generates a magnetic field that attracts the iron strip towards it.

• The striker strikes the gong (bell).

• When the striking arm strikes the gong, the contact is broken and current stops flowing through the circuit.

• This causes the electromagnet to lose its magnetic field.

• The connected spring arm returns the striker to its original rest position.

• The contact is restored and current flows through the circuit (provided the main switch is still pressed).

• The process is repeated from the beginning.

INPUT :

SIMULINK MODEL

EXPLANATION

• The pulse generator is used to create square wave pulses at regular intervals. The block waveform parameters Amplitude,pulse width,period and phase delay,determine the shape of the output waveform.

• The switch block used is controlled by external physical signal.If the external signal is greater than the thresold parameter then the switch is closed, otherwise switch is open.
• The positive terminal of the switch is connected to switch and the negative terminal is connected to the electrical reference.
• The Solenoid block is connected with switch and battery and we will get a complete electrical circuit.The port c is connected with mechanical reference.
• The ideal translational sensor is connected with solenoid block R to observe the movement of the plunger.
• Scope is connected with the ideal translational sensor to get the output.
• PS-Simulink converter is used to convert the physical signal to simulink signal.
• Solver Configuration:Each physical network represented by a connected simscape blocks requires solver setting information for simulation.

OUTPUT :

SCOPE OF PULSE GENERATOR

SCOPE OF IDEAL TRANSLATIONAL MOTION SENSOR

• Time period given is 2 seconds to the Pulse generator to open and close the switch.When the switch is closed the solenoid blocks receives electrical power from the battery and the plunger move from port R to c to hit the bell and produce sound.

AIM#2

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

THEORY :

THERMISTOR : thermal resistor is defined as a type of resistor whose electrical resistance varies with changes in temperature. Although all resistor's resistance will fluctuate slightly with temperature, a thermistor is particularly sensitive to temperature changes.

Thermistors act as a passive component in a circuit. They are an accurate, cheap, and robust way to measure temperature. While thermistors do not work well in extremely hot or cold temperatures, they are the sensor of choice for many different applications. Following is the Simulink block assembly for Thermistor based heater. And with condition follows here as :

1. 0-10 sec temperature 293

2. 10-30 secs temperature 300

3. 30-50 secs temperature 296

and you can see these details in plot basis in signal builder block where the input is inserted with these signals.

INPUT :

EXPLANATION

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.

Signal builder creates the input source according to the questiion asked in challenges.

Now the signal builder gives an input to controlled temperature source. An output of controlled temperature source is connected with thermistor. while double click the thermistor block it will shows some values the block are given below,

The temperature values are initiate in kelvin (K)

• An power supply like battery and current sensor is connected with the thermistor. And negative side are connected with electrical reference where solver also intitate in this circuit to obtain output.
• Scope is connected here with current sensor to find the output graph of current.

• The current sensor is connected to switch by Ps-simulink convertor. In the switch block the threshold value is entered by obtained output value that is get from current sensor.

If statement is used to turn on the fan in certain temperature that are asked in challenge

• 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

Therefore the ouput of switch block is connected to scope to plot the results.

OUTPUT :

CONCLUSION :

#Doorbell

• In above results the switch is closed the electromagnet receives electrical power from the battery and pulls the metal arm to hit the bell producing sound.
  • The motion of the plunger was simulated and recorded and plotted by using an IDEAL MOTION SENSOR and SCOPE block.

#Thermistor

• Thermistor is used to sense the temperature of a heater & turn on or turn off the fan as per above conditions
• Therefore the fan conditions are executed by SWITCH block and plotted in SCOPE block.