Week -2

simulation of a doorbell using solenoid

Aim:To implement a simulink block circuit using solenoid and provide on and off timer respectively as per needed.

Blocks used:

• Solenoid
• buzzer
• Single Pole Single Throw(SPST)switch
• translational motion sensor
• battery
• Pulse generator
• mechanical reference
• electrical reference

Initially the pulse generator is used to provide impulse signal . Its initial conditions are y(t)=amplitude if x=t else y(t)=0.

The pulse generator is used to provide on time and off time to SPST switch.

SPST switch -

The Single-Pole Single-Throw (SPST) switch controlled by an external control signal vT. If vT is greater than the threshold, then the switch is closed, otherwise the switch is open.If a non-zero threshold width is defined, then the switch conductance varies smoothly between off-state and on-state values as vT varies between threshold and threshold plus threshold width. The threshold width must be zero to enable switched linear solver optimizations.

The battery positive terminal is conected to SPST switch.

Solenoid-

This block implements the electrical and mechanical characteristics of a solenoid. Parameterization is in terms of two points [X1,F1] and [X2,F2] on its force-stroke curve for a 100 percent duty cycle at Rated voltage Vdc and Rated current Idc where X2>X1>0 are stroke values and F1>F2>0 are corresponding forces. The plunger fully in (i.e. air gap closed) corresponds to X=0, and pull-in force is assumed to decrease quadratically with the magnitude of X. To ensure the force remains finite, the following condition should hold: X2/X1>sqrt(F1/F2).

The plunger Maximum stroke is implemented as a hard stop, the dynamics of which are set by the Contact stiffness and Contact damping parameters. The same parameters are used to model the contact dynamics when the plunger pulls fully in. The Spring constant parameter is used to implement a spring force that pulls the plunger out, and can be set to zero.

Translational motion sensor:

a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity and position. 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 and 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.

mechanical reference:

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).

Output diagram shows that the impulse provided is on for 2 seconds and off for 2 seconds which was the required condition .The plunger is moved from its initial position for a small time and turns off immediately.

Cooling system for heater using thermistor

Aim: To implement a cooling system using thermistor for given set of temperature values

• Blocks used:
• Signal builder block
• thermistor
• voltage sensor
• display
• switch
• ideal angular velocity source
• DC motor
• Angular motion sensor
• solver configuration
• mechanical reference
• electrical reference
• ps-simulink converter
• simulink-ps converter

Circuit diagram explaination:The circuit consists of 3 parts mainly.They are : 1:Temperature sensing part

2:dc motor part (cooling part)

3:Control part

First part consists of temperature sensing part.Basically here signal builder block is used as a signal simulator for the given temperature values

time in seconds	0	10	30	50
temperature in degree celcius	20	20	27	23
temperature in kelvin	293.15	293.15	300.15	296.15

temperature in kelvin is needed because it is the si unit and by default it is accepted by signal builder block.The temperature signal is given to thermistor.The characteristic equation of an NTC thermistor is R=R0*e^(B(1/T - 1/T0)).

Where R0 is the nominal resistance at reference temperature T0,B is the temperature constant.A NTC type thermistor implies that the resistance of the thermistor is inversely propotional to temperature i.e.as temperature increases resistance decreases.One of the end is connected to thermal reference and A terminal is connected to signal builder block and the output terminal is connected to resistor of value 5k ohm.Overall use of thermistor is to convert temperature into equivalent electric potential.The voltage sensor block is used for converting voltage produced into physical signal because here thermistor is of physical type(simscape).The output of thermistor is taken through ps-simulink converter to the switch.The condition used for switch is U2 >=threshold .Here threshold is the voltage derived from thermistor and not temperature so the equivalent voltage for 25.1 0c is 10.02314v dc.

The switch is connected again to controlled voltage source via simulink-ps converter .This is done in order to maintain ideal voltage source for the time when temprature is greater than threshold i.e. 25 0c.

The output of controlled voltage source is given to which maintains a constant voltage independent of current flowing through it hence V=Vs.The output of switch is also given to ideal angular velocity source which provides angular velocity independent of torque.It has 3 terminals R,C,S.The S is the input port wherein the control signal in physical signal is provided with other two being rotational and conservative terminals respectively.The R terminal is connected to DC motor R terminal and C is connected to C terminal respectively.To measure the rotational motion an ideal rotational motion sensor is connected and finaly the output is taken through ps-simulink converters.

The 2 solver configuration blocks are connected both to the signal builder block and dc motor block respectively for solving the ode(first order differential equation) .

In the output diagram the motor turns on when temperature is above 25 0c and turns off when it falls below 25 0c.