Week -2

1) Simulink model for door bell using solenoid

condition: The switch must be closed for 2 seconds

Basic knowledge regarding solenoid: solenoid is made by wounding metalic wires on iorn core in order to provide magnetic properties.The strength of the magnetic field depends upon the current flowing through it and the number of turns.

Blocks required for creating model

(1) solenoid

(2)battery

(3)switch( when we select the switch from simulink library we can see that it has to be feeded by a source)

(4) translational motion sensor(as the bell consist of mechanical componets we need a translational motion sensor to detect the motion)

(5) solver function( mandatory of simulink model)

(6)electrical and mechanical referance (since we have electrical and mechanical operative parts we require this reference for the solver function)

(7)scopes( for viewing input, output, and for input output comparison)

(8) source(pulse generator for providing high and low and the time range is selected as 4 and pulse width as 50%) for satisfying given condition

(9) ps to simulink and simulink to ps converters for converting signals to corresponding singnals required for the respective blocks

Theoratical working of an electric bell: As from the given figure it is clear that when the switch is closed the current flows from postive to negative direction and the solenoid get energised, the energised solenoid attracts the plunger when the plunger got attracted the circuits get broken due to the movement of plunger and when the plunger moves backwards again the circuit get closed and this operation continues till the switch get opened

Inorder to achieve the condition we have to only do is to control the operation of threshold of the switch and the souce taken is the pulse generator

as the plunger is vibrating the output will be in small ranges.the input image of the scope and output images are attached in the input image we can see that the switch gets on and off between a time period of 2.from 0-2 sec its on and from 2-4 its off

output: on viewing the scope 1 which represents the position of motion we can see thatfrom 2-4 its off and hence the given condition is satisied

2) THERMISTOR CHALLENGE(to sense the temperature of a heater and to switch the fan if the temperature goes above 25 celcius(298)

condition: The input from the provided source has to be 20^0(293 k) for 0-10 seconds,27(300) celcius from 10 to 30 seconds,23 celcius(296) from 30 to 50 seconds

On viewing the given condition it is clear that the fan will be on between 10-30 seconds where the temperature is 27 >25. and in FAQ it has noted clearly that the temperature must be provide in the kelvin range. we know the covertion equation(K=C+273) where k= kelvin temp, c= celcius scale temp and 273 constant

BLOCKS REQUIRED

(1)THERMISTOR: a semiconductor device whose electrical resistance varies with change in temp. here we take an NTC(NEGATIVE TEMP CO EFFICIENT)thermistor.that is resistance and temperature are inversely proprtional for this thermistor

(2)resistance block which is in series with thermistor( so same current across it)

(3)ideal votage sensor block acroos the resistor for determing the voltage and the value varies as the value of restance varies for thermistor with temperature and the same current flows through the succeding resistor( since they are in series connection) whose value is known and using this sensor we can detect the voltage valuesfor different inputs

(4)battery( for thermistor)

(5)controled thermal source for feeding input to thermistor

(6) thermal reference( since we used thermal source the solver function require a thermal refernce)

(7)switch( with three inputs provided in FAQ) Feeded with the voltage from the voltage sensor and the threshold of the switch is put as the voltage corresponds to 25 celcius(298 k) for satisfying the given condition

(8)constant block( for proving high and low to switch for switching depending upon the threshold)

(9)electrical reference( since we used battery the solver function require electrical reference)

(10) solver function block mandatory

(11)ps to simulink and simulink to ps converters for converting singnals as required by their respective blocks

(12) scopes: for viewing inputs, outputs and for comparing them

(14)signal builder block( which is given as the input to controled thermal source)

Input:

first I made the input of the signal builder as 298(25) kelvin and the time range has changed to 50 seconds by doing this i got the value read by the voltage sensor on the display provided on the output of voltage sensor an i made this value as the threshold of the switch for getting the given condition of switching the fan to be satisfied.After that i changed the input of signal builder by clicking on the corresponding pulse and arranged for 293k for 0-10 seconds and 300k for 10-30k and 296 fro 30-50 k and the output has verfied by providing a scope at the output port of signal builder. The input condition image is shown below

output: as per the given condition it is clear that the fan will be on between 10;30 seconds where the temperature is above 298 kelvin. the image of scope is attached

remarks : the simulink model with motor is also attached by replacing switch of fan