LVQ Basic Electronics

Define the term "semi-conductor."

A semiconductor is a material that conducts electricity better than an insulator but not as well as a conductor. Its ability to conduct electricity can be controlled by adding impurities, changing temperature, or applying an electric field.

Explain the electrical properties of a diode.

A diode is a semiconductor device that allows electrical current to flow primarily in one direction and opposes current flow in the opposite direction.

Using a breadboard and a DC power supply, determine the voltage drop across a diode when forward and reversed biased.

Voltage drop across diode is 0.6 VDC when forward biased.

Voltage drop across diode is Power Supply voltage when reverse biased.

Indentify the appropriate voltage level for signals involving transistors.

The appropriate voltage level for signals involving transistors depends on the type of transistor, its circuit design, and the supply voltage.

• Low signal level: Typically 0–0.7 V for many silicon transistor base-emitter control situations, depending on operating conditions.

• Digital logic signals: Commonly 0 V for LOW and 3.3 V or 5 V for HIGH, depending on the logic family and transistor circuit.

• BJT transistor: A silicon base-emitter junction typically requires about 0.6–0.7 V to conduct significantly.

• MOSFET transistor: The gate-to-source voltage (\(V_{GS}\)) needed to turn it on depends on the device. Some use 3.3 V or 5 V logic; others require higher voltages.

Important: The base-emitter voltage of a BJT is not the same as the voltage required to drive a transistor circuit's input signal. Always check the manufacturer's datasheet for the correct operating voltage.

Explain the operation of Silicon Controlled Rectifier. Identify typical applications for this device in industrial applications.

A Silicon Controlled Rectifier (SCR) is a semiconductor switching device used to control the flow of electrical current. It acts as an electronically controlled switch and is commonly used to control high power in industrial electrical circuits.

Explain the operation of a Metal Oxide Varistor. Identify typical applications for this device in industrial applications.

They are used for absorption of transient voltage, suppression of pulse noise and circuit voltage stabilization.

Applications

• Surge Protection in consumer electronics

– industrial electronics

Explain the operation of a Light Emitting Diode. Identify typical applications for this device in industrial applications.

Light Emitting Diode (LED)

A Light Emitting Diode (LED) is a semiconductor device that produces light when electric current flows through it in the forward direction. This process is called electroluminescence.

Explain the function of a "reactor" when used in a power circuit.

A reactor in a power circuit is an inductive device, similar to a coil, used to limit or control the flow of electrical current. It is made from a coil of wire, often wound around an iron or magnetic core.

Explain the concept of reflective reactance. Identify the hazards and mitigation techniques of this phenomenon.

Harmonics running across the wire with long lead to motor. Mitigate by keeping motor leads as short as possible, or use load reactors.

Explain the operation of an Insulated Gate Bipolar Transistor. Identify typical applications for this device in industrial applications.

High speed switching applications (VFD's)

Explain the function of an opto-isolator. Identify typical applications for this device in industrial applications.

An opto-isolator, also called an optocoupler, is an electronic device that transfers an electrical signal between two circuits using light while keeping the circuits electrically isolated from each other.