Week -2
AIM (1) : - To make simulink model for a doorbell using solenoid block.
Blocks used in the simulink model :
1) Pulse generator
2) battery
3) Switch
4) Simulink - PS converter
5) PS - Simulink converter
6) Solenoid
7) Ideal translational motor sensor
8) Mechanical translational reference
9) Electrical reference
10) Solver configuration
11) Scope
* Switch is closed for 2 seconds and then released as per given conditions. The pulse generator is used to create square wave pulses at regular intervals and the block waveform parameters,amplitude,pulsewidth, period and phase delay determine the shape of the waveform.
Switch block is controlled by external physical signal & Positive terminal is connected to the block and negative terminal to 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 solenoid block R to observe the movement of the plunger.Scope is connected with ideal translational sensor to get output.
The signal from the pulse generator is converted using the Simulink - PS converter and is given to the input switch.A solenoid was introduced and the battery was connected to 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 the ideal translational motion sensor connected to the circuit.The scope is connected to visualize its behaviour.The spring constant and the damping parameters of the solenoid were altered to obtain the deired graph.
The simulation was run for 80 seconds and we can observe that the bell was ringing for every 2 seconds.
Conclusion:- When the switch is closed the solenoid block receives electrical power from the battery and the plunger moves from port R to C to hit the bell and produce sound.Physical movement of the plunger is observed by using translational motion sensor and physical output is converted into Simulink output model is displayed in the scope. By reducing the spring constant value and inctreasing the damping value vibrations will be reduced.
Aim (2) :- To use thermistor to sense temperature of a heater and to turn on & off a fan.
THERMISTOR :- Thermistor is a device to measure temperature based on the resistance.The resistance of a thermistor increases or decreases with respect to temoerature.The output from the thermistor is generally in the form of voltage or current.The increase in voltage or current indicates increase in temperature.
Conditions - Temperature source 20degrees from 0 to 10sec, 27degrees from 10 to 30 sec, 23degrees from 30 to 50 sec (temperature in Celsius), a Fan should be ON if the temperature is above 25 degree Celsius and OFF otherwise.
Simulink model explaination:-
A Signal bulider block is added to input the values
At point 1, time = 0 to 10 sec, temp = 293K
At point 2, time = 10 to 30 sec, temp = 300K
At point 3, time = 30 to 50 sec, temp = 296K
All temperature values must be converted to Kelvin before giving as inputs. A contolled temperature source block is to be used so that it represents the ideal source of thermal energy.It can maintain controlled temperature difference regardless of thr heat flow rate. 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 and voltage source represents AC/DC.
Electrical reference blockis given.Solver configuration - Each physical network represented by the connected simscape blocks requires solver setting information for simulation.
Controlled temperature source:- This block represents an ideal source of thermal energy that is powerful enough to maintain specific temperature difference across source regardless of the heat flow consumed by the sysytem.
Resistor :- This is the linear resistor described with the following equation, V=I.R,where V = voltage ,R = Resistance,I = current.
Voltage sensor :- This device converts the voltage measured between two points of an electrical circuit into physical signals proportional to the voltage.
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 atleast one electrical reference block.
In this model we have to find the threshold value of voltage at 25 degree celsius using signal block to find the position where Fan should be turned on and that value should be assigned to Switch block.
Conclusion :- 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.
Simulink models and output plots from the scope blocks are provided.