Week -2

SECTION A

Aim - Simulate a model of doorbell using solenoid block.

Objectives-

• Simulate a doorbell using solenoid block in simulink
• Create a situation where the switch is closed for 2 seconds and then released
• Observe the physical movement of the plunger.
• Use a thermistor to sense the temperature of a heater & turn on or turn off the fan

Concept of door bell

Operation of door bell

When you press a doorbell button, you complete an electrical circuit that allows household electricity to flow through the doorbell's internal electromagnet. The magnetic field generated by the electromagnet is then used to power a mechanism that creates the doorbell sound. it simply means that we required power source, switch, valve etc.

Simulink blocks required to create model and their use

• Pulse generator - to generate a pulse for 2 seconds as per our condition
• Battery - to provide a power source to circuit
• Switch - to on/off circuit
• Solenoid - to convert electric energy into mechanical energy
• Ideal Translational Motion Sensor - to detect weather there is any linear motion in the solenoid block during the simulation.
• Scope - to store the output
• Mechanical Reference
• Electrical reference
• Solver configuration block
• Simulink to ps converter
• Ps to Simulink converter

Simulink Model

Explanation of the model

• Creating a new model and save it
• adding pulse generator block and set parameters like amplitude 1, period 4 seconds, Pulse width 50
• Adding a switch block and connect it to a pulse generator using simulink to physical signal convertor
• Adding a battery and connect it to switch
• Adding a electrical reference and connect to battery
• Adding a solenoid
• adding a ideal translational motion sensor and to solenoid
• adding a scope to store output and coonect to ideal translational motion sensor through physical to simulink convertor
• Adding Mechanical reference and connect to relative port c of solenoid and ideal translational motion sensor
• adding a solver and connect it to model
• Run the model for 10 seconds
• captures the output

Set parameters for pulse generator

Output

Observation -

• As we can see from the above plot, The motion is getting 'generated' for '2 sec' and staying 'idle' for '2 sec' and this loop is getting repeated throughout the 'simulation time'
• We can see that this motion can be transferred to the arm which is connected to a doorbell, thereby producing sound whenever there is motion in the solenoid block.

SECTION B

Aim - Use a thermistor to sense the temperature of a heater & turn on or turn off the fan

Objectives -

• 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

Theory for thermistor

A Thermistor is a type of Resistor whose Resistance dependent on temperature, more so than is standard resistors. The word is a combination of thermal and resistor. Thermistor are widely used as inrush current limiters, temperature Sensor (negative temperature coefficient or NTC type typically), self-resetting overcurrent protector, and self-regulating heating elements (positive temperature coefficient or PTC type typically).

Thermistors are of two opposite fundamental types:
1. With NTC Thermistor, resistance decrease as temperature rises. An NTC are commonly use as Temperature Sensor, or in series with a circuit as an inrush current limiter.
2. With PTC Thermistor, resistance increases as temperature rises. PTC Thermistor is commonly installed in series with a circuit, and use to protect against overcurrent conditions, as resettable Fuse

Thermistors are generally produced using powdered metal oxides. With vastly improved Formula and Technique over the last 20 years, NTC Thermistor can now achieve accuracies over wide temperature range such as (+-0.1)’C or (+-0.2)’C from 0 degree Celsius to 70 degree Celsius with the excellent long term Stability. The typical operating temperature range of a Thermistor is (-55) degree Celsius to (+150) degree Celsius, though some glass body Thermistor have a maximal operating temperature of (+300) degree Celsius.
Thermistor differ from resistance temperature detector (RTDs) in that the material used in Thermistor is generally a ceramic or polymer, while (RTDs) use pure metals. The temperature response is also different RTDs are useful over large temperature ranges,while Thermistor typically achieve a greater precision within a limited temperature range, typically -90 degree Celsius to 130 degree Celsius

Blocks required to generate a simulink model

1. Signal Builder block-

The Signal Builder block allows you to create interchangeable groups of piecewise linear signal sources and use them in a model. You can quickly switch the signal groups into and out of a model to facilitate testing. In the Signal Builder window, create signals and define the output waveforms. To open the window, double-click the block.

2. Controlled tempreture source

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

3. Thermistor

A Thermistor is a type of resistor whose resistance dependent on temperature, more so than in standard resistors. The word is
combination of Thermal + Resistor.

4. Resistor

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

5. Switch

The Switch block passes through the first input or the third input signal based on the value of the second input. The first and third inputs are data input. The second input is a control input. Specify the condition under which the block passes the first input by using the Criteria for passing first input and Threshold parameter

6. Voltage sensor

The Voltage Sensor block represents an ideal voltage sensor, that is, a device that converts voltage measured between two points of an electrical circuit into a physical signal proportional to the voltage.

7. Constant block

The Constant block generates a real or complex constant value signal. Use this block to provide a constant signal input. The block generates scalar, vector, or matrix output, depending on following parameter
The dimensionality of the Constant value parameter
The setting of the Interpret vector parameters as 1-D parameter
The output of the block has the same dimensions and elements as the Constant value parameter

8. Simulink PS convertor

This Block convert simulink signals into physical signal for operational use in Model. for smooth signaling filter of input is required to set this enable signal filtering and input handling

9. Physical to simulink convertor

The PS-Simulink Converter block converts a physical signal into a Simulink output signal. Use this block to connect outputs of a Physical Network diagram to Simulink scopes or other Simulink blocks.

10. Electrical Referance

The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connected to ground must be connected to an Electrical Reference block. A model with electrical elements must contain at least one Electrical Reference block.

11. Battery

In Battery positive terminal is connected with switch and negative terminal is connected to Electric Reference

12. Solver

Each physical network represented by a connected Simscape block diagram requires solver settings information for simulation. The Solver Configuration block specifies the solver parameters that your model needs before you can begin simulation.

13. Scope

Scope is connected with Ideal Translation Motion Sensor to get the output. The real-time Scope block acquires data in chunks of size Number of samples from the real-time application that is executing on the target computer.

Calculating threshold value

to calculate a threshold value we can use constant block using maximum temp in kelvins which is 300k.

Final Model

Procedure and explanation

• To create a Simple Fan Cooling Model using Thermistor,Battery,Resistor,Voltmeter, a logical switch which are basic component of the circuit we need in Simulink model.
• First to represent a Thermistor, a Thermistor Block is taken and placed in model. Now to represent Battery, a Battery Block istaken and the positive terminal of this block is connected to positive port of the Thermistor Block
• Now to represent a Resistor, a Resistor Block is taken from Library browser and its positive port is connected to negative port of Thermistor Block. The negative port of Resistor Block is connected to negative port of Battery Block. Now a ElectricalReference Block is connected near the negative terminal of the Battery Block which represent the Earthing of the real time circuit.
• Now to represent a Voltmeter a Voltage Sensor Block is connected parallel to the Resistor Block, because to measure the voltage across a component, voltmeter should always connected parallel to that component
• Thus, we have completed our simple circuit Model, but we need some Physical Quantities to as Signal for Thermistor to work
• . In this case we need the Fan to get ON and OFF at different temperatures. So , to provide temperature , we have used Controlled Temperature Source Block which will gives a specified temperature as output even though heat flow is more.
• 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 Signal Builder Block which allows us to send any type of signal as inputs.
• We have to double click on the Signal Builder Block to set the signal configuration according to our requirement

At Point-1 - Time 0 sec - Temperature is 293K,
At Point-2 - Time 10 sec - Temperature is 293K,
At Point-3 - Time 10 sec - Temperature is 300K,
At Point-4 - Time 30 sec - Temperature is 300K,
At Point-5 - Time 30 sec - Temperature is 296K,
At Point-6 - Time 50 sec - Temperature is 296K

• Above Figure shows how signals are set in the Signal Builder Block. As this Dialogue Box opens, first we have to click on Signal at the top and then select New then select Custom option. Now it will ask to give the value of Y-axis and X-axis. Since weknow that at which time, we need which temperature as mentioned in the starting. We can give those values in an array in this box and then the above figure signals are generated.
• We can see in the figure that how different temperatures are given at different 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 Physical Value. So, to do this we have used a Simulink-PS Converter Block.
• 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
• Now the output of the Voltage Sensor Block is connected to Scope Block first and before connecting to the Scope Block a PS-Simulink Converter is used to convert Physical value to Simulink values.
• As mention in the objectives fan should be ON when the temperature is more than 25 degree Celsius i.e. 298.15K, from the above graph when voltage is more than 0.011 the Fan should get ON and when the Voltage is below 0.011, Fan should get OFF
• This above Logic used to ON and OFF the Fan. To do this we have used a “Switch Block” that routes the Signal according to the conditions provided.
• The center port of Switch Block is connected to output of PS-Simulink Converter” which gives the Voltage values. The top port of the Switch Block is connected to a Constant Block of value ‘1’ and the bottom port of the Switch Block is connected to another Constant Block of value ‘0
• The center port of Switch Block is the condition input which means that when the value from Voltage Sensor Block is more than the Threshold value in the Switch Block then it will pass the value ‘1’ which we have specified in the top port of the Switch Block If the Voltage from the Voltage Sensor Block is less than the Threshold value in the “Switch Block then it will pass the value ‘0’ which we have specified in the bottom port of “Switch Block”. Here it acts like a Transistor in Real time Circuit
• To set the Threshold value of the Switch Block, we have to Double click on the Switch Block and then we can change the
  value of Threshold. Since we want to be ON only when the temperature is 300K so the Threshold value is given as 0.011. so when the Voltage gets more than 0.011 the Switch will give value ‘1’ as output which means Fan will be ONN and when Voltage get less than 0.011 the Switch will give value ‘0’ as output which certainly means Fan will get OFF
• Now the output of Switch Block is connected to another “Scope Block” to get results
• By Double clicking the Scope Block we can observe the above Graph.

Final Output

Conclusion

• Thus, both the objective was achieved successfully.
• Similar approach can be used for simulating other Physical Device using Simulink
• Fan temperature was sensed by the thermistor in the Heater Model.