Project 6 - SIMULINK - control logic - Ringer & Thermistor.

AIM:  SIMULINK MODEL FOR DOORBELL & THERMISTOR.

OBJECTIVE:

     1.  To make Simulink model for a doorbell using solenoid block.

     2.  To use thermistor to sense temperature of a heater and turn on/off the fan.

EXPLANATION:

   SIMULINK MODEL:  

    A doorbell using solenoid block.

Simulink

model explanation –

We have used following blocks in the model

1. Pulse Generator.
2. Switch.
3. Battery.
4. Solenoid.
5. Ideal Translational motor sensor.
6. Mechanical translational reference.
7. Electrical reference. 8. Scope

            As per given conditions switch is closed for 2 seconds & then released. 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 shape of the waveform. Switch block is controlled by external physical signal & if the external physical signal is greater than the switch is closed or else switch is open. Positive terminal is connected to block while as, the negative terminal is connected to the electrical reference. When we connect solenoid block with the switch and battery we form a complete electrical circuit.

           The port c is connected with mechanical reference. The ideal translational sensor is connected with the solenoid block R to observe the movement of the plunger. Scope is connected with the ideal translational sensor to get the output. The signal from the pulse generator was converted using the Simulink PS converter and is given to the input switch. A solenoid introduced and battery is connected to the it. The voltage of the battery connected was made as same as that of the rated voltage of the solenoid.

             The switch is also connected to the same circuit. The position of the solenoid plunger is measured using an ideal translational motion sensor connected to the circuit. The initial position of this is set to 5mm in the translational motion sensor. The scope is connected to visualize its behaviour. The spring constant and damping parameters of the solenoid block was altered to obtain the desired graph.

Screen shoot while programing –

The simulation was run for 30 seconds and result obtained is shown above. It can be observed that at each 2seconds bell was ringing.

RESULTS –

Conclusion   –

              Conclusion for Door Bell Giving input as time period for 2 seconds in the pulse generator to open & close the switch. When the switch is closed the solenoid block receives electrical power from the battery and plunger moves from port R to port C to hit the bell & produce sound.

              Physical movement of the plunger is observed by using translational motion sensor & physical output is converted into Simulink output model is displayed in the scope. By reducing the spring constant value and increasing the damping value vibrations will be reduced.

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SIMULINK MODEL 2 :  

Thermistor for temperature of a heater and turn on/off the fan.

Thermistor –

Temperature source – 20 from 0 to 10 seconds, 27 from 10 to 30 seconds, 23 from 30 to 50 seconds

Fan conditions – ON if temperature above 25 degrees, OFF otherwise.

Simulink model explanation –

Signal building block is added to input the values as per given conditions.

At point 1, time = 0 sec. to 10 sec. & Temperature = 293K.

At point 2, time = 10 sec. to 30 sec. & Temperature = 300K.

At point 3, time = 30 sec. to 50 sec. & Temperature = 296K.

Controlled temperature source represents an ideal source of thermal energy that can maintain controlled temperature difference regardless of the heat flow rate. The temperature difference is set by the physical signal port S. A positive temperature difference causes the temperature at port B greater than the temperature at port A.

 Thermistor is a type of resistor whose resistance is based upon the temperature.

A linear resistor is used to control the amount of current from the battery.

The voltage sensor is used to convert the voltage measured between two points into physical signal & voltage source represents AC/DC.

Electrical reference block is given.

Solver configuration – each physical network represented by the connected simscape blocks requires solver setting information for simulation.

WHAT IS THERMISTOR?

Thermistor is a device which measures temperature, its working is based on the relationship between resistance and temperature. Here in Simulink the thermistor block which is available is a positive temperature co-efficient thermistor. So here resistance of thermistor increases or decreases with respect to temperature. the output from the thermistor is actually in the form of voltage or current. The increase in voltage/ current indicates increase in temperature.

Detailed temperature source –

Controlled temperature source-

This block represents an ideal source of thermal energy that is powerful enough to maintain specified temperature difference across source regardless of the heat flow consumed by the system.

Connection at point A & B are thermal observing ports corresponding to the source of inlet & outlet respectively. port S is the physical signal port through which the control signals that drive the source is applied.

Thermistor –

It is a type of resistor whose resistance depends upon temperature dependent on temperature, more than in standard resistors. This thermistor word is a combination of thermal & resistor.

Resistor –

This is the linear resistor, described with the following equation

V = I.R Where, V = Voltage I = Current R = Resistance

Voltage sensor –

This device converts the voltage measured between two points of an electrical circuits into physical signals proportional to the voltage.

It implements the voltage source with DC/AC & Noise components.

Electrical Reference –

It represents an electrical ground. Electrical conserving ports of all the blocks that are directly connected to the ground must be connected to the electrical reference port. A model with electrical components must contain at least one electrical reference block

       In this model the signal block is used to get temperature signal for the controlled temperature source (heater). The temperature of the heater is supplied to thermistor to sense it. Now in order to run the fan when temperature reaches the value of 298K we have to trigger the circuit with some external supply of battery and as there is no device to calculate the resistance value of thermistor so we have attached another resistor in series across the terminal in series.

       The voltage sensor is attached across the resistor to calculate the voltage drop into it & this voltage drop value is inputted as threshold value to the switch to start the fan & fan will go on when threshold value is more than 0.109.

Screenshot while programing –

Result -

       From 0-10 seconds fan is OFF because the temperature is 293K which is below 298K, after 10 seconds it goes to 300K, so fan will turn ON because temperature exceeds 298K. After 30 seconds fan will turn OFF because temperature goes 296K less than 298 K.