Week -2

Aim : Preparing the Simulink model for Doorbell and a thermistor to sense the heater temperature.

Objective :

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 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.

DOOR BELL

A solenoid is a device comprised of a coil of wire, housing, and a moveable plunger (armature). When an electrical current is introduced, a magnetic field forms around the coil which draws the plunger in. More simply, a solenoid converts electrical energy into mechanical work.

Components used in the circuit :

• Solenoid
• Switches
• Electrical power supply (DC)
• A bell with pivoted lever
• Some motion sensor for solenoid

simulink model:

explanation:

1. Pulse Generator: The Pulse Generator block generates square wave pulses at regular intervals. The block waveform parameters, Amplitude, Pulse Width, Period, and Phase delay, determine the shape of the output waveform.

2. Simulink-PS Converter: Converts the unitless Simulink input signal to a Physical Signal.

3. Scope: Display signals generated during simulation.

4. Switch: Switch controlled by an external physical signal.

5. Battery: The Battery block represents a simple battery model.

6. Solenoid: Model electrical characteristics and generated force of solenoid.

7. Ideal Translational Motion Sensor: The Ideal Translational Motion Sensor block represents a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity or position. You can specify the initial position (offset) as a block parameter. The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, and so on.

8. Mechanical Translational Reference: The Mechanical Translational Reference block represents a reference point, or frame, for all mechanical translational ports. All translational ports that are rigidly clamped to the frame (ground) must be connected to a Mechanical Translational Reference block.

9. Electrical Reference: The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connected to the ground must be connected to an Electrical Reference block. A model with electrical elements must contain at least one Electrical Reference block.

10. Solver Configuration: The Solver Configuration block specifies the solver parameters that your model needs before you can begin the simulation.

11. PS-Simulink Converter: Convert physical signal into Simulink output signal.

figure: Velocity plot for plunger

Objective 2:

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

THEORY:

A thermistor (or thermal resistor) is defined as a type of resistor whose electrical resistance varies with temperature changes. Although all resistors’ 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.

SIMULINK MODEL:

This figure shows the representation of thermistor connection which senses the temperature of a heater and passes the signal to a switch where a threshold limit is already set. If the temperature is above or equal to the threshold limit, then it gives "1" as output which is "Switch On". If the temperature is below the threshold limit, then it will give "0" as output which means "Switch Off". The input signal is generated with the help of a "Signal Builder" block . This signal is created according to the conditions given in this challenge. The conditions are as following:

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.

Here the temperature is converted in Kelvin from degree Celcius because the signal converter does not take °C value as input. I also have to set the signal unit as "Kelvin" in Simulink-PS Converter.

The formula for conversion: 1 °C= 273.15 K

The Signal 1 is:

From 0-10 sec- Temperature is 293.15 K

From 10-30 sec- Temperature is 300.15 K

From 30-50 sec- Temperature is 296.15 K

Figure - signal builder block

SWITCH :

explanation:

• At first, the signal is created in "Signal Builder" and further passes to "Simulink-PS Converter" to convert the input signal into the physical signal.
• This physical signal is connected to a block "Controlled Temperature Source". This block is connected to the thermistor and a "Thermal Reference" block.
• The thermistor is a part of an electric circuit where a battery, a voltage sensor, a resistor connected parallel to the voltage sensor, an electrical reference are connected to make a complete circuit. A solver configuration is connected to that electrical circuit to solve all parameters before the beginning of the simulation.
• The voltage sensor senses the temperature in the form of voltage and sends the data to its port "V".
• From this port, we get our output and send it to two different "PS-Simulink Converter".
• From converter-1, the signal is sent to the threshold switch. In the switch, the threshold limit is set to .0119641076. If the temperature is above or equal to the threshold limit, then it gives "1" as output which is "Switch On". If the temperature is below the threshold limit, then it will give "0" as output which means "Switch Off". The input signal is generated with the help of a "Signal Builder" block .
• The switch is connected to the scope where we can see our output plot.
• From converter-2, it converts the physical signal into a Simulink signal and sends the voltage data from the Voltage Sensor to display. This display gives us the threshold value of voltage. This value is set in the switch.

OUTPUT: