Build a Simulink model for Doorbell using solenoid block and a Thermistor to sense the temperature of a heater & turn on or turn off the fan.

2) Battery :-

• This block models a battery. If you select Infinite for the Battery charge capacity parameter, the block models the battery as a series internal resistance and a constant voltage source.

• If you select Finite for the Battery charge capacity parameter, the block models the battery as a series internal resistance plus a charge-dependent voltage source defined by:

         V = Vnom*SOC/(1-beta*(1-SOC))

         where SOC is the state of charge and Vnom is the nominal voltage. Coefficient beta is calculated to satisfy a user-defined data point [AH1,V1].

 3) Switch :-

• The block represents a switch controlled by an external physical signal. If the external physical signal PS is greater than the threshold, then the switch is closed, otherwise the switch is open.

• The closed resistance is defined by parameter R_closed, and the open conductance is defined by parameter G_open. Both parameters must be greater than zero.
• The block has two electrical conserving ports and one physical signal port PS.

4) 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. 

• The following diagram shows how each parameter affects the waveform.

• The Pulse Generator block can emit scalar, vector, or matrix signals of any real data type. To emit a scalar signal, use scalars to specify the waveform parameters.
• To emit a vector or matrix signal, use vectors or matrices, respectively, to specify the waveform parameters. Each element of the waveform parameters affects the corresponding element of the output signal.
• For example, the first element of a vector amplitude parameter determines the amplitude of the first element of a vector output pulse. All the waveform parameters must have the same dimensions after scalar expansion. The data type of the output is the same as the data type of the Amplitude parameter.
• The block output can be generated in time-based or sample-based modes, determined by the Pulse type parameter.

         Output pulses:

          if (t >= PhaseDelay) && Pulse is on

          Y(t) = Amplitude

          else

          Y(t) = 0

          end

• Pulse type determines the computational technique used.
• Time-based is recommended for use with a variable step solver, while Sample-based is recommended for use with a fixed step solver or within a discrete portion of a model using a variable step solver.

5) Ideal Translational 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.
• Connections R and C are mechanical translational conserving ports that connect the block to the nodes whose motion is being monitored. Connections V and P are physical signal output ports for velocity and position, respectively.
• The block positive direction is from port R to port C. This means that the velocity is measured as v = v_R – v_C, where v_R, v_C are the absolute velocities at ports R and C, respectively.

6) Scope :-

• This block is used to display signals during simulation.

7) Mechanical Translational Reference :-

• This block represents a mechanical translational reference point, that is, a frame or a ground. Use it to connect mechanical translational ports that are rigidly affixed to the frame (ground).

8) Electrical Reference :-

• Electrical reference port. A model must contain at least one electrical reference port (electrical ground).

9) Simulink-PS converter :-  Converts the Simulink input signal to a Physical Signal.

10) PS-Simulink Converter :- Converts the input Physical Signal to a Simulink output signal.

Simulink Model :-  Doorbell circuit using Solenoid block

Model Drive Link :-

 https://drive.google.com/file/d/1dLUeHIeuGJhpcyTItBzSj42r8ukQ3rNz/view?usp=sharing

Input Graph :-

Output Graph :-

Explanation :-

• Initially, we have used Pulse Generator block to provide input square shaped waveform at regular intervals. Then, we have altered the parameters by keeping amplitude as 1, period of signal as 4 sec, Pulse width of 50% and phase delay of 2 sec.
• The details are as under;

• This means that initially the pulse will be zero and at 2 secs, the pulse width will be half of period(50%), so for the next two seconds the pulse will be at amplitude ’1’ only, then it will again come down to zero at 4^th second and then it will at zero for next 2 secs thus completing the periods of 4 seconds.
• From starting to ending of the pulse will take 4 secs of time periods in which only for 2 secs the amplitude will be one and for rest of time it will be zero. So, after these 4 secs period again the pulse will be generated and thus cycle continues.
• To this ‘Pulse Generator block’ a ‘Scope block’ is connected to see how the pulse is generated.
• As mentioned before, the pulse has started after 2 seconds, then for next two seconds it has amplitude of ‘1’ and then next 2 seconds the pulse is again zero. The pulse is starting from 2 seconds and ending at 6 seconds which nothing but a time period of 2 seconds.
• Thus, this represents that when amplitude is one, the switch will be closed and when it is zero the switch will open. Since our objective is only to see the change in position of plunger when switch is closed for 2 seconds so that we have the amplitude as 1 for 2 seconds in the pulse generator by making the pulse width half of the period in the inputs for ‘Pulse Generation block’.
• Thereafter, we have used Simulink-PS converter block because switch block requires an external physical signal to operate. If external physical signal applied is greater than threshold value, then switch is closed otherwise it is open.
• Further, we have taken Solenoid block and connected positive terminal of Solenoid block with positive terminal of Battery. Also, we have connected negative terminal of solenoid block to negative terminal of battery block.
• Now, the battery, switch and solenoid block is connected to ‘Electrical Reference block’ which represents the earthing of the circuit. The ‘Electrical Reference block’ should be connected with the negative terminal of the ‘Battery block’.
• Now, in the ‘Solenoid block’, ‘R’ and ‘C’ are two variables which represent the Plunger and fixed point respectively.
• Now this ‘R’ is connected to an ‘R of the ‘Ideal Translational Motion Sensor block’, which senses the position of the plunger in the ‘Solenoid block’ and gives the output.
• Now in the ‘Ideal Translational Motion Sensor block’, the outputs are given as V and P which represent the velocity and the position of the plunger. Since, we need to observe only the position of the plunger, we need the results from ‘P’ output.
• Now the ‘C’ in the ‘Ideal Translational Motion Sensor block’ represents the mechanical translational conversion port which means that the mechanical process starts from ‘R’ and ends at ‘C’ and it again starts from ‘R’ and the cycle goes on.
• So ‘C’ in the ‘Ideal Translational Motion Sensor block’ is connected to a ‘Mechanical Translational Reference block’ which represents a fixed point where it is rigidly clamped in real time.
• Similarly, ‘C’ of the solenoid block is also connected to the same ‘Mechanical Translational Reference block’ as fixed point for the solenoid.
• Since, we need the position of the plunger as output from ‘Ideal Translational Motion Sensor block’, so we have connected the port ‘P’ to a ‘PS-Simulink Converter block’ where the physical values of the port ‘P’ are converted to Simulink value which is connected to the ‘Scope block’ for generating the graph of the change in the position of the plunger from port ‘P’ of ‘Ideal Translational Motion Sensor block’.
• As mentioned above the port ‘P’ of ‘Ideal Translational Motion Sensor block’ is connected to another ‘Scope block’, and a ‘Solver Configuration block’ is also connected to this path which generates equations and solves the whole model internally to give the results of the whole Simulink model as output.
• Further, we have ran the model and double clicked on the ‘Scope block’ which is connected to ‘Ideal Translational Motion Sensor block’ to see the results.
• From the above figure, we can observe that the initial position of the plunger is at ‘5’, as from the pulse generator block, a pulse generated at 2, so in the position of the plunger is also changing at time 2 seconds and time till which the pulse amplitude is ‘1’ till that time the plunger is also at same position after the change from initial position.
• Again, as the amplitude of the pulse becomes zero, the plunger returns to its initial position back again and as the pulse cycle goes on, plunger also changes its position and comes back to its initial position.
• We can also observe that when there is a change in position of the plunger, there are some wave forms at the start of changes in position. This is due to recoil of the spring, each time when the plunger is moving. So to reduce this, in the ‘Solenoid block’ we can reduce the spring constant value and increase the damping co-efficient. This will reduce the waves that are being formed and we will get a smooth graph.
• The above figure is a smoother graph. This is done by changing the values of spring constant and damping in the ‘Solenoid block’ as under;

PART 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

SOLUTION :- 

Theory :-

Thermistor :- 

• A thermistor was first discovered by Michael Faraday in 1833 on a silver sulfide which showed a behavior of decrease in resistance when temperature increased.

• A thermistor is a semiconductor that has a resistance capacity more than a conducting material and less than insulating material. Its electrical resistance varies with the change in the temperature or thermally sensitive resistor. There are mainly two types of thermistors, namely the Negative Temperature Coefficient (NTC) and the Positive Temperature Coefficient (PTC).

• Thermistor’s relation with temperature also depends on the material in which it is made. A negative temperature coefficient (NTC) thermistor will decrease its resistance value when temperature increases whereas a Positive temperature coefficient (PTC) will increase its resistance when temperature increases.

• The electronic symbol of the thermistor is given below;

• NTC thermistors are widely used in industries for different applications like temperature measurements, temperature control, and different applications NTC is an integral part of. PTC is mostly seen in circuit protection, current-limiting resistors.

• Thermistors have high sensitivity which can be up to 10 percent change per degree celsius and their typical response time is 0.5 to 5s with an operating range from -50 to ~300 °C and there are devices with more capacity.

        Circuit Diagram :-

Different Types of Blocks used in Simulink model are as under;

1) Thermistor Block :-

• The Thermistor block represents an NTC thermistor using the B-parameter equation. The resistance at temperature T is

        where:

     The following equation describes the thermal behavior of the block:

      where: