Week -2

1. Here first we are going to study the Simulink model of the doorbell using a solenoid block. We need to access the Simulink with the block parameters to run the simulation. First, we need to get to understand the theory behind the Doorbell mechanism.

Theory of Doorbell:

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. Press the button in the diagram below to see how this works.

In this design, 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. This is the "ding" sound.

As long as you hold the doorbell button, the 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.

The Principle behind Doorbell:

The solenoid is an electromagnet with wire winding and a small metal piston inside it. ... When electric current flows through the wire, an electromagnetic field is generated which pulls the metal piston towards it. The metal piston hits the tone bar located on both sides of the arrangement.

Now we set up the Simulink and simscape block setup for the solenoid doorbell. We need to understand what are the blocks involved and why they are involved. What are their characteristics and what role they play in the doorbell simulation?

PS-Simulink and Simulink-PS converter, Scopes, Displays, Pulse generator, electrical and mechanical references, solenoid, Battery, switch, ideal Transalation motion sensor, solver configuration. These are the following simscape and Simulink blocks that are going to use in this simulation.

PS-Simulink and Simulink-PS converter: These are basically the converter from Physical systems to Simulink signals and vice versa.

Scopes: Gives the plot of the output

Pulse generator: is an analog input that has amplitude and frequency with which the input is transmitted.

Electrical and Mechanical references: is a reference block with which the system has a ground source as a base.

Solenoid: is an electromagnetic device that is represented as a block here.

Battery: is a device that has a negative and positive terminal for the electric circuit to be completed for an electric flow.

The Switch is a device the completes the electric circuit for current flow and can be controlled manually or automatically depends on the type of switch required.

Ideal Translated motion sensor: It's a type of sensor which provides the position or velocity input for the system to generate output.

Solver Configuration: It's a type of block that acts as a complete equation for where f(x) = 0 where we find the value of x and generate the output which represents the block diagram as an equation.

Before we begin the simulation we need to setup an input parameter here in pulse generator where we delay seconds should be 2 secs with amplitude 1 and Pulse time should be 4 secs to make it in half with 50% pulse width.

And here is the Full simulation with all the simscape and Simulink block system.

Output:

The input signal of the Pulse generator:

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

we going to use the same procedure as above to simulate a thermistor to sense the temperature of a heater.

Thermistor: thermal resistor is defined as a type of resistor whose electrical resistance varies with changes in temperature. Although all resistor's resistance will fluctuate slightly with temperature, a thermistor is particularly sensitive to temperature changes.

Thermistors act as a passive component in a circuit. They are an accurate, cheap, and robust way to measure temperature. While thermistors do not work well in extremely hot or cold temperatures, they are the sensor of choice for many different applications. Following is the Simulink block assembly for Thermistor based heater. And with condition follows here as :

1. 0-10 sec temperature 293

2. 10-30 secs temperature 300

3. 30-50 secs temperature 296

and you can see these details in plot basis in signal builder block where the input is inserted with these signals.

NOTE: Before we run we need to provide an integrated input in the Simulink-PS converter block to be able to read the for systems.

Simulink and simscape block design:

after running for 50 secs we need to provide the display as an input to the switch for ON and OFF conditions.

And therefore we get the output as follows: