Electronics Summary Notes

Summary Notes for Electronics Types of Switches 1. SPST (Single-Pole, Single-Throw) • Symbol: • How it Works: Two contacts, either open or closed. • Application: Simple on-off switch. Can be used to switch the power supply to a circuit. • Real-World Example: Light switches in homes. 2. SPDT (Single-Pole, Double-Throw) • Symbol: • How it Works: Three contacts. Also called a changeover switch. • Application: Can operate two parts of a circuit. For example, used to switch on a red lamp in one position and a green lamp in the other position. • Real-World Example: Railway signal controls. 3. DPDT (Double-Pole, Double-Throw) • Symbol: • How it Works: Six contacts. A pair of on-on switches that operate together. • Application: Can operate two different circuits at the same time. Can be wired up as a reversing switch for a motor. • Real-World Example: Forward and reverse control in electric motors. Name of Switch Type of Switch Physical Attributes to Differentiate Real-World Applications & Examples Slide Switch SPDT or SPST SPDT has three positions, left, middle, right SPST slides between two positions only. SPDT: Used in electronic toys like remote-controlled cars. SPST: Used in simple DIY electronics projects. Rocker Switch SPST Generally only two positions: ON and OFF. Used in computer power strips and some study lamps. Toggle Switch SPDT or DPDT SPDT has three positions, left, middle, right DPDT has more and may have a locking mechanism. SPDT: Used in model airplanes for control selection. DPDT: Used in robotics projects for motor direction control.

Name of Switch Type of Switch Physical Attributes to Differentiate Real-World Applications & Examples Push- button Switch SPST or SPDT SPST usually stays in one position until pushed again. SPDT returns to the original position when released. SPST: Used in computer power buttons. SPDT: Used in arcade game machines. Press Switch SPST (Momentary) Only one position; returns to OFF when released. Used in school laboratory emergency stop buttons and computer keyboards. Micro Switch SPST or SPDT SPST usually has two terminals SPDT has three. SPST: Used in 3D printers for end- stop detection. SPDT: Used in DIY electronics projects for safety features. Reed Switch SPST Generally only two positions: ON and OFF, activated by a magnet. Used in simple magnetic door alarms.

Types of Capacitors Type of Capacitor Function Similarities Differences Real-World Applications & Examples Electrolytic Stores electric charge; higher capacitance for more charge storage. All types store electric charge. All types are measured in Farads (F), microFarads (uF), nanoFarads (nF), or picoFarads (pF). - Has polarity; must be connected correctly. - Usually has a coloured strip to indicate polarity. - The negative terminal is usually shorter. Used in DIY speaker projects to filter audio signals. Non- Electrolytic Stores electric charge; generally lower capacitance than electrolytic. - Does not have polarity; can be connected either way. - No coloured strip. Used in simple LED flasher circuits for school projects. Variable Capacitor Stores electric charge; capacitance can be varied by applying voltage. - Capacitance values can be varied. - Used for tuning circuits. Used in DIY radio projects to tune to different stations. Key Points: • Capacitance: The amount of charge a capacitor can store. Measured in Farads (F), microFarads (uF), nanoFarads (nF), or picoFarads (pF). • Polarity: Electrolytic capacitors have polarity and must be connected correctly, while non-electrolytic capacitors do not have this requirement.

Types of Sensors Sensor Type How It Functions How Resistance Varies Light Sensing (LDR) Senses the amount of light in the environment. Resistance decreases as light intensity increases. In bright conditions, the resistance is low, allowing more current to flow. Moisture Sensing (Metal Rods) Senses the amount of moisture in the soil or environment. Resistance decreases as moisture levels increase. In damp conditions, the resistance is low, allowing more current to flow. Temperature Sensing (Thermistor) Senses the temperature of the environment. Resistance decreases as temperature increases. In warm conditions, the resistance is low, allowing more current to flow. Key Points: • Light Sensing (LDR): Light-dependent resistors (LDRs) are used for both light and dark sensing. Their resistance changes based on the amount of light they are exposed to. • Moisture Sensing (Metal Rods): Metal rods act as sensors whose resistance changes based on the moisture content between them. • Temperature Sensing (Thermistor): Thermistors are temperature-sensitive resistors whose resistance changes based on the temperature of the environment they are placed in.

Transistors and Thyristors Component Function Similarities Differences Real-World Applications & Examples Transistor Used to switch and amplify electronic signals and power. Acts as an automatic switch and amplifier. Both are semiconductor devices used for controlling current. Both have the ability to control current in circuits. - Three terminals: base, collector, emitter. - Controlled by current at the base. - Can be turned on and off repeatedly. Used in simple DIY electronic projects like LED flashers and alarms. Thyristor Used to control high power and is often used in alarm systems. Once triggered, it remains on until manually reset. - Three terminals: anode, cathode, gate. - Controlled by current at the gate. - Once triggered, remains on even when no current flows into the gate. Used in projects like intruder alarms and other sensor-based systems. Key Points: • Terminals: Transistors have base, collector, and emitter terminals, while thyristors have anode, cathode, and gate terminals. • Control: Transistors are controlled by the base, whereas thyristors are controlled by the gate. • State: Transistors can be turned on and off repeatedly, while thyristors, once triggered, remain on until manually reset.

Types of Sensor Circuits Sensor Type Function of Transistor Switch Circuit How Circuit Functions How Current is Channelled Real-World Applications & Examples Light Sensing Turns on a Bulb / LED / Buzzer when it senses light. - Uses a Light- dependent resistor (LDR) as a sensor. - Variable resistor adjusts sensitivity. - In bright conditions, low resistance in LDR allows current to flow into the base of the transistor, lighting up the bulb. Current flows from the LDR into the base of the transistor, activating the Bulb / LED / Buzzer. Used in DIY projects to create alarms that go off when a light is turned on, like a "door-open" alarm for a locker. Dark Sensing Turns on a Bulb / LED / Buzzer in dark conditions. - Similar to the light- sensing circuit but configured to activate in darkness. - In dark conditions, high resistance in LDR allows current to flow into the base of the transistor, lighting up the bulb. Current flows from the LDR into the base of the transistor, activating the Bulb / LED / Buzzer in darkness. Used in DIY projects to create night lights that turn on automatically when it gets dark. Moisture Sensing Lights up a Bulb / LED / Buzzer when it senses moisture. - Uses metal rods as sensors. - In damp conditions, low resistance between rods allows current to flow into the base of the transistor, lighting up the LED. Current flows from the metal rods into the base of the transistor, activating the Bulb / LED / Buzzer. Used in school projects to create alarms for plant watering systems. Temperature Sensing Lights up a Bulb / LED / Buzzer - Uses a thermistor a