Week -2
AIM:
1.Make a Simulink model of Doorbell using solenoid block.
2.To make the simulink Using a thermistor to sense the temperature of a heater & turn on or turn off the fan.
SOLENOID:
A solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix. The coil can be arranged to produce a uniform magnetic field in a volume of space when an electric current is passed through it. The term solenoid was coined in 1823 by André-Marie Ampère to designate a helical coil.
In the study of electromagnetism, a solenoid is a coil whose length is substantially greater than its diameter. The helical coil of a solenoid does not necessarily need to revolve around a straight-line axis; for example, William Sturgeon's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape.
In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion.[5] In simple terms, a solenoid converts electrical energy into mechanical work. The term is also often used to refer to a solenoid valve, an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid or linear solenoid. Solenoid bolts, a type of electromechanical locking mechanism, also exist. In electromagnetic technology, a solenoid is an actuator assembly with a sliding ferromagnetic plunger inside the coil. Without power, the plunger extends for part of its length outside the coil; applying power pulls the plunger into the coil. Electromagnets with fixed cores are not considered solenoids.
THERMISTOR:
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).
Thermistors are of two opposite fundamental types:
- With NTC thermistors, resistance decreases as temperature rises usually due to an increase in conduction electrons bumped up by thermal agitation from valency band. An NTC is commonly used as a temperature sensor, or in series with a circuit as an inrush current limiter.
- With PTC thermistors, resistance increases as temperature rises usually due to increased thermal lattice agitations particularly those of impurities and imperfections. PTC thermistors are commonly installed in series with a circuit, and used to protect against overcurrent conditions, as resettable fuses.
Thermistors are generally produced using powdered metal oxides. With vastly improved formulas and techniques over the past 20 years[when?], NTC thermistors can now achieve accuracies over wide temperature ranges such as ±0.1 °C or ±0.2 °C from 0 °C to 70 °C with excellent long-term stability. NTC thermistor elements come in many styles such as axial-leaded glass-encapsulated (DO-35, DO-34 and DO-41 diodes), glass-coated chips, epoxy-coated with bare or insulated lead wire and surface-mount, as well as rods and discs. The typical operating temperature range of a thermistor is −55 °C to +150 °C, though some glass-body thermistors have a maximal operating temperature of +300 °C.
Thermistors differ from resistance temperature detectors (RTDs) in that the material used in a thermistor is generally a ceramic or polymer, while RTDs use pure metals. The temperature response is also different; RTDs are useful over larger temperature ranges, while thermistors typically achieve a greater precision within a limited temperature range, typically −90 °C to 130 °C.
GOVERNING DIAGRAM:
FOR SOLENOID:
Basic components used to generate a simple doorbell circuit are:
1.Battery
2.Switch
3.Solenoid
4.A bell with plunger.
FOR THERMISTOR:
Basic components used to generate a simple cooling fan circuit are:
1.Battery
2.Thermistor
3.Fan
4.Transistor
5.Resistor
OBJECTIVES:
FOR DOOE BELL:
Create a situation where the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.
FOR FAN:
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.
SIMULINK MODEL:
DOOR BELL:-
EXPLANATION:
1.From the above govrning circuit of a door bell,we know that we need a switch,solinoid,battery and plunger.
2.so,in order to get all these components into simulink model we have to taken blocks that perfoem same action what the above devices perform.
3.noe first 'solenoid block' is taken to represent the battery we have taken 'battery block' from the library browser.
4.then this 'solenoid block' and 'battery block' are connected to eacch other via positive and negative terminals.
5.A 'switch block' is placed in between 'solenoid block' and 'battery block' and it is connected with the both blocks.
6.Now for the switch to operate we need to provide a physical signal through 'ps' port in the 'switch block'. the provided physical signal should be greater then the threshold of the switch, forthe switch being closed,or else it will be open.
7.Now this whole battery,switch and solenoid path is connected to an electrical refeerence block' with represented earthing of circuit.this 'electrical reference block' should be connected connected with the negative port of the battery.
8.then the 'solenoid block', 'R' and 'C' are two variables which represented plunger and fixed points respectively.
9.now this 'R' is connected of ideal tranlation motion sensor block',which senses the position.of the plunger in the 'solenoid block' and gives the output.
10.Now the 'ideal translation motion sensor block' the outputs are given as 'V' and 'P' which is represented the velocity and position of the plunger.since we are only intrested is knowing the change in posiytion of te plunger,so we need only results from 'P' output.
11.Now 'C' the 'ideal translation motion sensor block' is a mechanical translation conserving port,which means that the mechanical process starts from'R' and ends at 'C' and again it starts at 'R' and cycle goes on.
12.So 'C' in the 'ideal translation motion sensor block' is connected to a 'mechanical translation reference' which represented a fixed point where it is rigidly clamped in real time.
13.similarly 'C' of 'solenoid block' is also connected to the same 'mechanical translation reference' as fixed points for the solinoid.
14.Since we position of the plunger as output from 'ideal translation motion sensor block' we have connected port 'P' as 'PS- simulink converter' where the physical values from port 'P' are converted in to simulink value,and then this 'PS-simulink converter' is connected to 'scope block' which will generate a graph for change in position of plunger from port 'P' of ideal translation motion sensor block'.
15.Now to provide a physical signal for operating the switch,we have used a 'pulse generator block',which generate countinuous square pluse.
16.From the above figure we can observe that we have taken wehave given period values as '4',pulse width as'50',phase delay as '2' and amplitude by default is '1' we have changed it.this means that initially the pulse will be zero,since we have given phase delay of '2' so till 2sec the pluse will be zero and at 2 sec the pulse will start from zero to 1 since we have given amplitude as '1' and then now pulse width will half of period,so for the next two seconds the pulse will be aat period,so for the next two seconds the pulse will be at amplitude '1' only,then it will be zero for next 2 secs thus completing the period of 4 seconds.
17.From starting to ending of the pulse it will take 4 secs of time period in which only 2 secs the amplitude will be one and the rest of time it will be zero.so,after these 4 secs period again the pulse will be generated and thus cycle countinuous.
18.to this 'pulse generator block' a 'scope block' is connected to see how the pulse is generated.
19.The above figure is obtained by running the simulink model and double clickig on the'scope1' block.this figure shows,how the pulse is generated and in this figure the x-axis reprsents the time and y-axis representsed the amplitude.as mentioned in the point no18, the pulse has started after 2 seconds then for next two seconds it has amplitude of '1' and then next two seconds and ending at 6seconds which nothing but a time period of two seconds.
20.thus this represents that when ampliyude 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 s closed for 2secs in yhe pulse generator by making the pulse width half of the period in the inputs foe 'pulse generator block'.
21.since the pulse that is coming from 'pulse generator block' is a simuling value,so to convert this value into a physicval value we have used 'simulink-ps converter block',since switch only takes value as inputs.
22.As mentioned above the port 'P' of 'ideal translation 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.
23.Now run the model and double click on the 'scope block' which is connected to 'ideal translation motion sensor block' to get the results.
24.we will get the above graph as the result when we double click on the 'scope block' here x-axis represents the time in seconds and y-axis represents position of plunger.
FOR FAN OPERATIONS USING THERMISTOR:-
EXPLANATON:-
1.To create a simple cooling fan model using thermistor we need a thermistor,battery,resistor,voltmeter,a logical switch which are basic compenents of the circuit we need in the simulink model.
2.First to represent a thermistor,a 'Thermistor block' is taken and placed in the model.now to represent a battery,a 'battery block' is taken and the positive port of this block is connected to positive port of the 'thermistor'.
3.now to represent a resistor,a'resistor block' is taken from the library browser and its positive port is connected to negative port of the 'battery block'. now a 'electrical referance block' is connected near the negative terminal of the 'battery block' which represents the earthing of the negative terminals of the 'battery block'which represents the earthing of the real time circuit.
4.Now the represent a voltmeter a 'voltage sensor block'is connected parallel to a 'resistor block',because to measure a voltage across a component,voltmeter should be always connected parallel to that component.
5.Thus,we have completed our simple circuit model,but we need some physical quanties to as sign foe thermistor to work.
6.In this case we need to turn ON and OFF at different temperature.so,to provide temperature,we used 'controlled temperature source block' which only gives a specified temperature as output even though heat flow is more.
7.now to give different temperature to this 'controlled temperature source block' we need to send temperature signals.to send these signals we have used a 'singular builder block' which allows use to send any type signal as inputs.
8.we have to double click on the 'signal builder block' to set signal according to our requirement.
GIVEN INPUTS:-
At point-1-time 0 secs - temperature is 293k
At point-2-time 0 secs - temperature is 293k
At point-3-time 0 secs - temperature is 300k
At point-4-time 0 secs - temperature is 300k
At point-5-time 0 secs - temperature is 296k
At point-6-time 0 secs - temperature is 296k
9.Above figure shows how the signal are set in the 'signal builder block'as thid dialogue box opens,first we have to click on the 'signal' at the top and select 'new' then select 'custom'option.now it will ask to give of y-axis and x-axis. since we know that the which time, we need which temperature as mentioned in the strating.we can give those values in an array in the above figure signals are generated.
10.We can see in the figure how differrent temperature are given time.so thus,we have created our signals and before connecting it to the 'controlled temperature source block' we have to convert these signals into a physical value.so,to do this we have used a'simulink PS covertor block'.
11.In 'simulink-ps converter block' in filtering and derivatives box set it as a filter inputs,derivatives calculation.
12.So now the port 'B' of 'controlled temperature source block' is connected to port 'A' of the 'thermistor block'and port 'A' of 'CONTROLLED TEMPERATURE SOURCE BLOCK' is connected to the 'thermal reference block'.in 'controlled temperature source block' a positive temperature difference causes the temperature at port B to be greater than the temperature at port A.
13.Now the output of the 'voltage sensor block'is connected to 'scope block' first,and before connecting to the 'scope block' a 'ps-simulink convertor' is used to convert physical values tosimulink values.
14.connect the 'display block' in the switch.
15.run the simulation see the value in the display block, and enter the value in the 'switch block'.
16.now again we run the simulation and double click on the 'scope block' we will get the following graph.
17.from the above figure we can see that how voltage is changing with change in tempearture.using this information,we can set conditions for fan ON and OFF.
18.if we observe the graph,we notice that from time 0 to 10 secs when temperature is 293k,voltage is between 0.0095 and 0.01 and from time 10 to 30 secs when the temperature is 300k,voltage is between 0.0125 and 0.013 and from time 30 and 50 seconds when temperature is 296k,voltage is nearly 0.011.
19.as mentioned in the objective fan should be ONN when temperature is more than 25degree celsius,from the above graph when the voltage is more than 0.011,fan should be OFF.
20.this above logic is used to ONN and OFF the fan.to do this we have used a 'switch block' that routes the signals according to the conditions provided.
21.the centre port 'switch block'is connected to output of 'ps=simulink convertor'which gives the voltage values.the top port of the 'switch block' is connected to a 'constant block' of the value 1 and the bottomport of the 'switch block' is connected to another 'constant block' of value 0.
22.the centre port of 'switch block' is the condition input which means that the value from 'voltage sensor block' is more than the thershold value in the 'switch block'then if it will pass the value 1 which we have specified in the top port of the 'switch block'.if the voltage from 'voltage sensor block' is less then the thershold value in the 'switch block'then it will pass the value 0 which we have specified in the bottom port of the 'switch block'.here its acts like a transistor in a real time circuit.
23.now the output of 'switch block'is connected to another 'scope block' to get the results.
24.by double clicking the scope block we can observe the above graph.here we can clearly see that when temperature is 300k the fan is ONN and at remaining temperatures the fan is OFF.
CONCLUSION:-
1.Thus,both the objectives were achieved successfully.
2.similar approach can be used for simulatinh other physical devices using simulink.