CORO: ⚡ Arduino & Electronic Circuitry — Comprehensive Flashcards

What is electricity?

Electricity involves the movement of electrons through a conductor due to an electrical potential difference.

What are the three fundamental electrical properties?

1. Voltage (V)

2. Current (I)

3. Resistance (R)

Remember:

V → I → R

What is voltage?

Voltage is the electrical potential difference or "pressure" that causes current to flow.

Unit: Volts (V)

What is a good analogy for voltage?

Pressure in a compressed tyre.

Higher pressure provides more force to push air out.

Similarly, higher voltage provides more electrical potential to drive current.

What is current?

Current is the flow of electric charge through a circuit.

Symbol: I

Unit: Amperes (A), commonly called amps.

What is a good analogy for current?

Think of water flowing through a pipe.

• Voltage → pressure pushing the water

• Current → water flowing

• Resistance → restriction slowing the water

What is resistance?

Resistance is the opposition/restriction to the flow of electric current.

Symbol: R

Unit: Ohms (Ω)

What is a good analogy for resistance?

Imagine trying to run through a swimming pool.

Water provides much more resistance to your movement than air.

Similarly, electrical resistance makes it harder for current to flow.

What are the units and symbols for voltage, current and resistance?

Property	Symbol	Unit
Voltage	V	Volts (V)
Current	I	Amperes/Amps (A)
Resistance	R	Ohms (Ω)

Memorise this table.

What particle is primarily responsible for electrical current in a conductor?

Electrons.

What happens inside a battery that creates a potential difference?

Chemical reactions separate charge, creating an imbalance of electrons between the terminals.

This creates a potential difference (voltage).

What happens when a conductor connects the two terminals of a battery?

The potential difference causes electrons to move through the conductor, producing electrical current.

What direction do electrons actually flow?

Electrons move from the negative terminal toward the positive terminal.

Electron flow:

− → +

What is conventional current?

Conventional current is the direction we use in circuit diagrams and calculations.

It is considered to flow from:

+ → −

What is the difference between electron flow and conventional current?

Electron flow:
− → +

Conventional current:

• → −

This is a classic test question.

What is Ohm's Law?

Ohm's Law describes the relationship between voltage, current and resistance.

The formula is:

V = I × R

What does each letter in Ohm's Law represent?

V = Voltage

I = Current

R = Resistance

Therefore:

Voltage = Current × Resistance

What happens to current if voltage increases while resistance stays constant?

Current increases.

Voltage and current are directly proportional when resistance remains constant.

What happens to current if resistance increases while voltage stays constant?

Current decreases.

More resistance makes it harder for current to flow.

What are the three rearrangements of Ohm's Law?

Voltage:

V = I × R

Current:

I = V ÷ R

Resistance:

R = V ÷ I

Memorise all three.

A circuit has 5 V and a resistance of 250 Ω. What current flows?

I = V ÷ R

I = 5 ÷ 250

I = 0.02 A

or

20 mA

How do you convert amperes to milliamperes?

1 A = 1000 mA

Therefore:

0.02 A = 20 mA

What does "directly proportional" mean in the context of voltage and current?

If resistance stays constant, increasing voltage causes current to increase proportionally.

For example:

1.5 V → 31 mA

Approximately:

3.0 V → 62 mA

So doubling voltage approximately doubles current.

What is a floating digital input pin?

A digital input pin is floating when it isn't connected to a definite HIGH or LOW voltage.

This can cause the Arduino to receive unpredictable readings.

Why is a floating pin a problem?

The Arduino may randomly interpret the pin as:

HIGH → LOW → HIGH → LOW

even though nobody is deliberately changing the input.

How can a floating input be prevented?

A pull-down resistor can connect the input pin to GND, giving it a definite LOW state when the switch is open.

Your notes specify a:

10 kΩ pull-down resistor.

What does a pull-down resistor do?

It ensures that an input pin has a defined LOW state when the button/switch isn't activated.

What happens when the button connected to a pull-down input is pressed?

The button connects the input to HIGH/5 V, causing the Arduino to read a HIGH signal.

What happens when the button is released?

The pull-down resistor holds the input at LOW/GND, preventing the pin from floating.

What is a pushbutton used for in an Arduino circuit?

It provides a digital input that allows a user to interact with the Arduino.

What are the two basic states of a digital button?

Pressed → HIGH/ON

Released → LOW/OFF

The exact electrical behavior depends on how the circuit is wired.

Why does the pushbutton need to be placed correctly on a breadboard?

The button must be positioned so that pressing it connects the appropriate sides of the circuit.

Incorrect placement can prevent the circuit from working correctly.

What Arduino function is used to configure a pin as an input or output?

pinMode()

What does this code do?

pinMode(2, INPUT);

It configures digital pin 2 as an input.

What does this code do?

pinMode(13, OUTPUT);

It configures digital pin 13 as an output.

What Arduino function reads the state of a digital input?

digitalRead()

What does this code do?

digitalRead(2);

It reads the current digital state of pin 2.

The result will normally be:

HIGH or LOW.

What is void setup() used for?

setup() runs once when the Arduino starts or resets.

It is commonly used to configure pins and initialise components.

What is void loop() used for?

loop() runs continuously/in an infinite loop while the Arduino is operating.

What is the difference between setup() and loop()?

setup() → runs once

loop() → runs repeatedly

Easy memory trick:

SETUP = Set things up once.
LOOP = Keep doing it. 🔄

What does this code mean?

void setup() {
    pinMode(2, INPUT);
    pinMode(13, OUTPUT);
}

When the Arduino starts:

• Pin 2 is configured as an INPUT

• Pin 13 is configured as an OUTPUT

Why does loop() need to run continuously in an interactive system?

So the Arduino can continuously check inputs, process information and respond with outputs.

What is the "Blinky" project?

A simple Arduino project where an LED is turned ON and OFF repeatedly.

It is often considered the hardware equivalent of "Hello World" in programming.

Why is the Blinky project useful?

It can verify that:

• The Arduino is powered.

• The wiring is correct.

• The LED circuit works.

• The program was uploaded correctly.

• The Arduino is executing the code.

What is an LED?

LED stands for Light Emitting Diode.

It is an electronic component that produces light when current flows through it in the correct direction.

What does it mean that an LED is polarized?

It means an LED must be connected in the correct direction for current to flow properly through it.

How can you identify the anode of a typical LED?

The anode is the positive side (+) and is typically associated with the longer leg.

How can you identify the cathode of a typical LED?

The cathode is the negative side (−) and is typically associated with the shorter leg.

What is the correct current path in the Blinky circuit?

Arduino Pin 13 → resistor → LED anode → LED cathode → GND

Why is a resistor placed in series with the LED?

To limit the current flowing through the LED and prevent excessive current from damaging the LED or circuit.

Why can't you connect an LED directly to a 5 V Arduino output?

Because without a current-limiting resistor, too much current could flow through the LED, potentially damaging it.

What voltage does the Arduino Uno provide when a digital output is HIGH?

Approximately 5 V.

If an LED has a 2 V voltage drop and the Arduino supplies 5 V, how much voltage must the resistor drop?

5 V − 2 V = 3 V

So the resistor must drop approximately 3 V.

What target current is used in your LED calculation?

20 mA

Convert to amperes:

20 mA = 0.020 A

How do you calculate the resistor value for the LED?

Use:

R = V ÷ I

The resistor voltage is:

5 V − 2 V = 3 V

Therefore:

R = 3 ÷ 0.020

R = 150 Ω

So the calculated resistor is:

150 Ω

Why did we subtract the LED's 2 V drop from the 5 V supply?

Because the LED uses approximately 2 V, leaving approximately 3 V that must be dropped across the resistor.

What happens if the resistance is too small?

Too much current may flow, potentially damaging the LED or other components.

What happens if the resistance is too large?

Less current flows, so the LED may be dimmer.

What Arduino function is used to set a digital output HIGH or LOW?

digitalWrite()

What does this code do?

digitalWrite(13, HIGH);

It sets digital pin 13 HIGH.

On the basic Blinky circuit, this turns the LED ON.

What does this code do?

digitalWrite(13, LOW);

It sets digital pin 13 LOW, turning the LED OFF in the basic Blinky circuit.

What does HIGH represent in a basic Arduino digital output?

Approximately 5 V on an Arduino Uno digital output.

What does LOW represent?

Approximately 0 V/GND.

What does delay() do?

It pauses the program for a specified amount of time.

What unit does Arduino's delay() use?

Milliseconds (ms).

How long is delay(1000)?

1000 milliseconds = 1 second

Therefore:

delay(1000);

means:

Wait 1 second.

How long is delay(500)?

500 ms = 0.5 seconds

How long is delay(2000)?

2000 ms = 2 seconds

What does this program do?

void setup() {
    pinMode(13, OUTPUT);
}

void loop() {
    digitalWrite(13, HIGH);
    delay(1000);

    digitalWrite(13, LOW);
    delay(1000);
}

It repeatedly:

1. Sets pin 13 HIGH → LED turns ON.

2. Waits 1 second.

3. Sets pin 13 LOW → LED turns OFF.

4. Waits 1 second.

5. Repeats forever. 🔄

Why does the Blinky LED continuously flash?

Because the instructions are inside loop(), which Arduino executes repeatedly.

Explain how an Arduino interactive system works from input to output.

INPUT

A sensor/button provides information.

PROCESS

The microcontroller reads and processes the information.

OUTPUT

The Arduino controls an output such as an LED or motor.

REPEAT 🔄

The Arduino continuously repeats this process.

Explain a button-controlled LED system.

1. The button acts as an input.

2. Arduino uses digitalRead() to read the button.

3. The program checks whether the button is HIGH or LOW.

4. Arduino uses digitalWrite() to control the LED.

5. The LED turns ON/OFF depending on the program's logic.

How does hardware interact with software in an Arduino?

Hardware provides physical components such as:

• Buttons

• Sensors

• LEDs

• Motors

• Resistors

Software tells the microcontroller what to do with those components.

For example:

Button
  ↓
digitalRead()
  ↓
Program decision
  ↓
digitalWrite()
  ↓
LED

Is voltage the same thing as current?

No.

Voltage is the electrical potential/pressure.

Current is the flow of charge.

Is resistance the flow of electricity?

No.

Resistance is the opposition to current flow.

Does setup() repeat forever?

No.

It runs once at startup/reset.

Does loop() run once?

No.

It runs repeatedly.

Does digitalRead() control an LED?

Not directly.

digitalRead() reads an input.

digitalWrite() controls a digital output.

Remember:

READ = get information

WRITE = send/control information

Does delay(1000) mean 1000 seconds?

No.

It means 1000 milliseconds = 1 second.

Is an LED connected directly to 5 V without a resistor a good idea?

No.

A current-limiting resistor should be used to protect the LED.

What is Ohm's Law?

V = I × R

Find current when V = 5 V and R = 250 Ω.

I = V/R

I = 5/250

I = 0.02 A = 20 mA

Find resistance when V = 3 V and I = 0.02 A.

R = V/I

R = 3/0.02

R = 150 Ω

An Arduino supplies 5 V to an LED with a 2 V forward voltage and a target current of 20 mA. What resistor is required?

Voltage across resistor:

5 − 2 = 3 V

Current:

20 mA = 0.020 A

Therefore:

R = V/I

R = 3/0.020

R = 150 Ω