Creating a Simple Temperature Controlled Fan and Doorbell in Simulink

Q1. Make a Simulink model of Doorbell using a Solenoid Block

An electric bell is an electro-mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing, clanging, or ringing sound. The electric bell runs on the principle of a solenoid. An electric bell consists of one or more electromagnets, made of a coil of insulated wire around an iron bar, which attracts an iron strip armature with a clapper. When an electric current flows through the coils, the electromagnet creates a magnetic field which pulls the armature towards it, causing the hammer to strike the bell.

Doorbell Model in Simulink

The Component used to build the doorbell model are:-

1. Battery

A battery is a device consisting of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, mobile phones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal. 

2. Switch

A switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts are touching current can pass between them, while when the contacts are separated no current can flow.

3. Signal builder

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 using a signal builder.

4. Solenoid

A solenoid is a type of electromagnet, the purpose of which is to generate a controlled magnetic field through a coil wound into a tightly packed helix. The coil can be arranged to produce a uniform magnetic field in a volume of space when an electric current is passed through it. It is a type of transducer which converts electrical energy into linear motion.

5. Lever

A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load, and effort, the lever is divided into three types. Also, leverage is a mechanical advantage gained in a mechanical system. A lever amplifies an input force to provide a greater output force, which is said to provide leverage. The ratio of the output force to the input force is the mechanical advantage of the lever. As such, the lever is a mechanical advantage device, trading off force against the movement.

6. Translational Motion Sensor

The Ideal Translational Motion Sensor block represents a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity or position. You can specify the initial position (offset) as a block parameter. The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, etc.

7. Mechanical Translational Reference

The Mechanical Translational Reference block represents a reference point, or frame, for all mechanical translational ports. All translational ports that are rigidly clamped to the frame (ground) must be connected to a Mechanical Translational Reference block.

8. Electrical Reference

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

9. Solver Configuration

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 the simulation. Each topologically distinct Simscape block diagram requires exactly one Solver Configuration block to be connected to it.

10. Scope

Display signals generated during simulation.

11. Display

The Display block shows the value of the input data.

12. Converter

Converts the Simulink input signal to a physical signal and vice versa.

Concept for the Model

First, we create an input signal in which we have the signal for the switch to closed for 2 seconds and then released. The input signal is sent to the switch which turns 'on' and 'off' on the basis of the input signal. A battery, solenoid, and an electrical reference are connected in series with the switch. 

The sliding core inside the solenoid is connected to a mechanical lever with a linear motion sensor. A Spring is used with the core to bring the solenoid to its initial position once the switch is turned off. The linear movement of the solenoid is recorded using the scope and the value is displayed in the display block.

Input Signal

Simulink Model

Output from Scope

Q2. Use a Thermistor to sense the Temperature of a Heater & Turning the Fan on or off

Temperature control is a process in which change of temperature of a space (and objects collectively there within), or of a substance, is measured or otherwise detected, and the passage of heat energy into or out of the space or substance is adjusted to achieve the desired temperature. It uses thermal, mechanical, and electrical components to control the temperature.

Doorbell Model in Simulink

The Component used to build the doorbell model are:-

1. Thermister

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

Thermistors are of two opposite fundamental types:

With NTC thermistors, resistance decreases as temperature rises. An NTC is commonly used as a temperature sensor, or in series with a circuit as an inrush current limiter.

With PTC thermistors, resistance increases as temperature rises. PTC thermistors are commonly installed in series with a circuit and used to protect against overcurrent conditions, as resettable fuses.

2. Signal builder

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 using a signal builder.

3. Electrical Reference

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

4. Thermal Reference

The Thermal Reference block represents a thermal reference point, that is, a point with an absolute zero temperature, with respect to which all the temperatures in the system are determined.

5. Controlled Temperature Source

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

6. Battery

A battery is a device consisting of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, mobile phones, and electric cars. When a battery is supplying electric power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons that will flow through an external electric circuit to the positive terminal.

7. Resistor

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.

8. Voltage Sensor

A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. 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.

9. Switch

A switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts are touching current can pass between them, while when the contacts are separated no current can flow.

10. Solver Configuration

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 the simulation. Each topologically distinct Simscape block diagram requires exactly one Solver Configuration block to be connected to it.

11. Controlled Voltage Source

The ideal voltage source is driven by the input signal. The Controlled Voltage Source block represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current flowing through the source.

12. DC Motor

A DC motor is any of a class of rotary electrical motors that converts direct current electrical energy into mechanical energy. The most common types rely on the forces produced by magnetic fields.

13. Ideal Rotational Motion Sensor

The Ideal Rotational Motion Sensor block represents an ideal mechanical rotational motion sensor, that is, a device that converts an across variable measured between two mechanical rotational nodes into a control signal proportional to angular velocity or angle. You can specify the initial angular position (offset) as a block parameter. The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, etc.

14. Scope

Display signals generated during simulation. 

Concept for the Model

First, we create an input signal in which the temperature is 20 °C from 0 to 10 seconds, 27 °C from 10 to 30 seconds, 23 °C from 30 to 50 seconds. The temperature signal is sent to the thermistor using a controlled temperature source as the thermistor cannot take a physical temperature signal. 

Input Temperature Signal

Based on the temperature signal the thermistor increases and decreases the resistance in the loop. A resistor is used in the loop with a voltmeter meter to check the voltage difference across the resistor. The Voltage signal is sent to a switch using the convertor and threshold values is given corresponding to the desired temperature above which the fan switch will be turned on. The signal from the switch is sent to a controlled voltage source.

Signal from Switch

Based on the input signal controlled voltage source creates a potential difference across the DC motor. The DC motor converts the electrical signal to rotational motion which is sensed by the Ideal Rotational Motion Sensor. The output from the Sensor represents the running of the fan when the temperature goes above 25 °C.

Output from Rotational Motion Sensor

The Angular Velocity vs Time shows that the fan started to run at time of 10 seconds and stopped at 30 seconds. Our temperature was above 25 °C corresponding to the above mentioned time range.

Simulink Model

References

1. https://en.wikipedia.org/wiki/Electric_bell

2. https://en.wikipedia.org/wiki/Thermistor

3. https://in.mathworks.com/help/physmod/sps/ug/thermistor-controlled-fan.html