Basics of Electronics

Instructor: Tian Xia

Electrical Engineering Professor

A circuit that controls the light

What is behind and what are involved?

Operating Mechanism

• The battery generates electrical current and supplies electrical power.
• The electrical power is converted into both thermal energy and light energy to turn on the light bulb.

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Circuit Components:

• Battery
• Switch
• Light bulb
• Wires

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What else are involved?

• Electrons
• Voltage
• Current

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Courtesy: Atlearner.com

Electrons in Atom Structure

An atom is made up of electrons, protons, and neutrons

The nucleus contains the protons and neutrons.

The shell contains the electrons, which orbit the nucleus.

https://cognitoedu.org/coursesubtopic/c3-alevel-cie_cCQpEOkI

Electrical Current

Voltage (Electrical Potential)

Why would electrons move?

• Electrons are pushed by Voltage. It is the “push” or “pressure” that drives the movement of electrons, resulting in electric current.
• Voltage (symbol: ‘V’), is also known as electric potential difference --- the difference in electric potential energy between two points in a circuit. 
• Like water, current flows from areas of higher potential (e.g., the positive terminal of a battery) to lower potential.

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An analogy between a water system and an electrical circuit:

http://learn.olympiacircuits.com/electricity-flows-like-water.html

Circuit schematic

Resistor

• A resistor (symbol: ‘R’ )is a circuit element that limits the flow of electrons through a circuit, thereby reducing current flow.
• A resistor reduces the current flow by emitting some of the electrical energy in the form of thermal heat.
• The I-V curve of a resistor is a straight line with slope = 1/R.

Ohm’s Law

It defines the relationship between the components’ current I in amps (A), voltage V in volts (V) and resistance R in ohms (Ω).

Question: Calculate I in the circuit below.

Question:

Capacitor

https://www.vecteezy.com/vector-art/25747550-water-tank-analogy-for-a-capacitor-suitable-for-educational-products

https://www.allaboutcircuits.com/textbook/direct-current/chpt-13/electric-fields-capacitance/

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Inductors

https://www.allaboutcircuits.com/textbook/reference/chpt-1/inductor-sizing-equation/

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Light Emitting Diode (LED)

A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it.

Hands-on Experiment 1

• Developing an LED drive circuit using a breadboard.
• Using a multimeter to measure the voltage and the current.

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Applying the KVL:

Experiment 1: Design Procedure

1. Pick a Green LED from your kit.

https://www.facebook.com/nusrathelectric/posts/led-voltage-chart/2677724709129812/

https://www.kingbrightusa.com/images/catalog/SPEC/WP1503GT.pdf

https://soldered.com/learn/led-light-emitting-diode-explained/

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2. Pick a Quiescent point for the LED (datasheet).

We choose the closest value, which is 330Ω.

Assembling and testing

Current

(in Series)

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Voltage

(in Parallel)

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How Use Bread Board

Breadboards structure:

1. Horizontal rows (yellow and green lines)
2. Vertical columns
3. Power (red) /Ground (blue) Rails

The middle divider separates both sides. If you wire power and ground to one side of the breadboard, you will also need to power/ground the other side.

Measurement Instruments

1. Hand-held Multimeters

Can measure:

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• Voltage (AC and DC),
• Current (AC and DC),
• Resistance value (Ω),
• Diode Test,
• Continuity,
• Frequency,
• Capacitance.

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Measurement Probe Position

Series

(Current Measurement)

• To measure Current, the probes must be in series with the component.
• To measure Voltage, the probes must be in parallel with the component.

Measurement Instruments

1. Hand-held Multimeters

Can measure:

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• Voltage (AC and DC)
• Current (AC and DC)
• Resistance value (Ω)
• Diode Test
• Continuity
• Frequency
• Capacitance

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Measurement Instruments

2. Oscilloscopes

Can measure:

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• Voltage (AC and DC, over time),
• Signal frequency,
• Signal period and time intervals,
• Peak-to-peak voltage,
• Rise time and fall time,
• Waveform shape and distortion,
• Phase difference between signals,
• Signal noise,
• DC offset,
• Math functions,
• Bandwidth, etc.

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• Cannot directly measure current.

Appendix

KVL and KCL

Kirchhoff’s voltage law:

All voltages in a loop add up to 0.

Kirchhoff’s current law:

All currents entering/leaving a loop add up to 0.

Series and Parallel Connections

https://www.quora.com/What-is-the-difference-between-a-series-circuit-and-a-parallel-circuit-in-terms-of-current

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• In series circuits 🡪 Current is the same, Voltage is added up
• In parallel circuits🡪 Voltage is the same, and Current is split

Question

Find the parallel and series connections in the circuit below.

https://www.allaboutcircuits.com/textbook/direct-current/chpt-7/what-is-a-series-parallel-circuit/

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