Week -2

Aim: This challenge aims to make a Simulink model of a doorbell using a solenoid block and make another Simulink model where a thermistor will be used to sense the temperature of a heater & turn it on or turn it off the fan.

Objective:

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.

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

Theory:

The common chime design uses a solenoid to hit two tone bars in sequence.

A chime doorbell uses a specialized sort of electromagnet called a solenoid. A solenoid is just an electromagnet where the coiled wire surrounds a metal piston. The piston contains magnetically conductive metal, so it can be moved backward or forward by the electromagnetic field 

In many instances, the solenoid piston consists of an iron core mounted to a non-magnetic metal bar. When there is no power to the electromagnet, a spring pushes the piston to the left, and the iron core extends outside of the wire coil. When you turn the electromagnet on (by pressing the doorbell button), the iron core is drawn to the magnetic field, so it slides into the center of the coiled wire.

As the iron core slides to the right, the end of the piston strikes the right-hand tone bar. The tone bar vibrates, producing a particular note

As long as you hold the doorbell button, current will flow through the electromagnet and the piston will remain in this position. But when you release the button, the current will stop flowing through the electromagnet and the magnetic field will collapse. The spring snaps the piston back to the left, where it hits the tone bar on the other side. The second tone bar produces the "dong" sound.

You can make more elaborate tone sequences by adding more solenoids and tone bars. Some variations on this design produce a different tone pattern when someone rings the back doorbell than when someone rings the front doorbell. Each doorbell button closes a separate circuit, connected to separate solenoids in the doorbell mechanism. In the simplest design, one of the solenoids hits a bumper instead of the second tone bar. In this way, one doorbell button will trigger a "ding-dong" tone and the other button will trigger only a "ding" tone.

In recent years, more and more people have been installing electronic doorbells in their homes. An electronic doorbell doesn't have any electromagnets or tone bars. Instead, it has an integrated circuit (IC) that registers when the button has been pressed. The IC triggers a digitally recorded song or message. A lot of electronic doorbells have a wireless control system so the doorbell mechanism doesn't have to be specially wired.

Electronic doorbells are growing in popularity, but most homes still use conventional electromagnet doorbells. This classic design may not play elaborate songs or messages, but it is so simple and sturdy that it should be around for a long time to come

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

Blocks used in model:

Pulse generator;

Scopes;

electrical and mechanical references;

solenoid;

Battery;

switch;

Displays;

ideal Transalation motion sensor;

solver configuration;

PS-Simulink and Simulink-Ps converter;

These are the following simscape and Simulink blocks that are going to use in this simulation

Result: - TheSimulink model solenoid of Doorbell using  block of the givenIn 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 have simulink plotted.

2a)Fan conditions: ON if the temperature above 25 °C, OFF otherwise

Blocks used in model:

• Repeating Sequence Stair

• Controlled Temperature Source

 This model shows how fundamental thermal, mechanical and electrical components can be used to model a thermistor-controlled fan. The heat-generating device

This model shows how fundamental thermal, mechanical and electrical components can be used to model a thermistor-controlled fan. The heat-generating device starts producing 2 watts at time zero, and then at 40 seconds this increases to 20 watts. The thermistor therefore heats up, and its resistance decreases thereby increasing the voltage across the PWM reference pins. This increases the PWM frequency which in turn increases average motor current, and the fan speeds up. The additional fan speed increases the convective cooling of the device, moderating the temperature increase of the device.

This is a system-level model such as might be used for selecting an appropriate thermistor characteristic. The convective heat transfer coefficient used to model nominal cooling (i.e. when the fan isn't running) would typically be determined by experiment. Knowing the temperature difference and having an estimate of the device area, the heat transfer coefficient can be calculated. The coefficient for the fan-assisted cooling could then be estimated by running the motor at maximum RPM, and again measuring the temperature difference. The nominal cooling term just also be taken into account when calculating the fan-cooling coefficient.

The Controlled PWM Voltage and H-Bridge blocks have two modes of operation, namely Averaged and PWM. As this is a system-level model, and the thermal time constants are measured in seconds, the Averaged mode of operation is used. The PWM mode replicates the PWM control signal which would typically operate at a few kilohertz.

Result: - TheSimulink modelUse a thermistor to sense the temperature of a heater of the given In the above arrangement,Temperature source the electromagnet receives electrical power from the battery simulink model is plotted.

2b) Use a thermistor to turn on or turn off the fan as per the below conditions:

Fan conditions: ON if the temperature above 25 °C, OFF otherwise

Blocks used in model:

• Repeating Sequence Stair

• Controlled Temperature Source

The conditions of the temperature source is defined inside the above window. The sample time was taken as 10s and the whole simulation time was taken as 50s. Battery and a resistor is connected in the thermistor circuit. A voltage sensor was given accross this resistor to measure the voltage change during different temperature inputs. The resistance of this resistor can be set to any value, but it should not be changed once the threshold voltage is found. The threshold temperature was given as 25 degree Celsius and the corresponding voltage over the resistor was found out, through a display connected to the voltage sensor. At this time the Repeating Sequence Stair was given only one value, i.e, 25 degree Celsius or 298 K. The output from the voltage was also given into a switch which is linked to a lamp which displays different colours based on the logical conditions. The lamp color was set to red if the temperature was below 298K and to green when the temperature is above 298 K.

Results:

Result: - TheSimulink modelUse a thermistor to turn on or turn off the fan as per the below conditions of the given In the above arrangement,Temperature source the electricalmotor receives electrical power from the battery simulink model is plotted.