Creating a Doorbell model and a Temperature Sensor for Fan using Simulink

Week 2 Report.

1. Make a Simulink model of Doorbell using a solenoid block with the following details:

In the above arrangement, when the switch is closed the electromagnet receives electrical power from the battery and pulls the metal arm to hit the bell producing sound.

Create a situation where the switch is closed for 2 seconds and then released. Observe the physical movement of the plunger.

Assume remaining parameters.

Ans=>

In the electric bell when the switch is closed the electromagnet receives the electric power from battery and pulls the metal hammer to hit the bell producing

sound.

Part 1: Simulink model of Doorbell using solenoid block

Model=

The above model uses the following blocks

1.Pulse Generator

This block generates a pulse of amplitude 1 and for a duration of 2 seconds (50% of 4 seconds). This signal is then converted to Physical Signal using the Simulink-PS Converter block .

2. The Physical signal controls the switch shown below

The Switch remains closed if the physical signal is greater than the threshold.

3. The blue colored circuit shown is the electrical circuit which is controlled by the switch. When the circuit is closed the current flows from the battery to the solenoid which actuates the plunger.

The Battery used is 12V with 2 ohms internal resistance battery

4. Doorbell mechanism

The green circuit shows the doorbell mechanism

The Plunger moves when there is a current in the solenoid. The Plunger movement causes the doorbell to ring. The plunger motion is

measured by a translational motion sensor which is plotted by the scope block.

5.Solenoid

F1 and F2 are forces corresponding to X1 and X2. Rated voltage is the voltage required to power up the solenoid.

Parameters for the plunger mass, spring stiffness and damper coefficient.

6. Ideal Translational Motion Sensor:

It is the motion sensor which senses the plunger motion to plot the plunger motion versus time.

Results:

-Position Signal

For the first 2 seconds the electrical circuit is closed and the doorbell rings. At time = 2 seconds the circuit breaks and the spring pull the plunger back to its original position. Now, because of the spring stiffness the plunger oscillated for about half-a second which is nothing but damping effect.

To minimize the plunger oscillation we can increase damping coefficient of spring.

-Velocity Signal

2. Use a thermistor to sense the temperature of a heater & turn on or turn off the fan as per below conditions:

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

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Model:

Temperature is 20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds

Fan should be on if the temperature above 25 °C, off otherwise.

To generate the temperature conditions a signal builder is used with a controlled temperature source. The signal builder generates a simulink signal which varies with time as defined.

20 degrees from 0 to 10s

27 degrees from 10 to 30s

23 degrees from 30 to 50s

Fan Condition: ON if the temperature above 25⁰ C, OFF otherwise

Here in model from Signal Builder we have created temperature profile signal according to time duration requirements.

Which onwards converted to physical signal through converter block and send it to Controlled Temperature Source block.

This block represents an ideal energy source in thermal network that can maintain a controlled temperature difference regardless of the heat flow rate.The temperature difference is set by the physical signal port S.

Now this generated temperature is sense by Temperature Sensor block or either by Thermistor which senses equivalent temperature as resistance changes.

From temperature sensor block we have given condition by Switch block .

Like this Switch block will not generate signal until it crosses Threshold value of 25⁰ C.

So if temperature of input signal goes above 25⁰ C which is happening in condition 27 degrees from 10 to 30s . Thus Switch generate signal 1 as ON signal to trigger MOSFET which ultimately close the circuit and current draws from battery which can be used to ON Fan to cool the heater.

Result:

The output is as expected. The Fan is ON when temperature is greater than 25 degrees which is in between 10 - 30 sec and OFF otherwise.And SOC of battery decreases during Fan operation period only.