Circuit Components Reference

Your visual guide to all the components used in this course. Each section includes images, pinouts, and what the component does.

Need a datasheet? Google "[chip number] datasheet" - always available online!

Passive Components

Resistor

What it does: Limits current flow and creates voltage drops
Measured in: Ohms (Ω), kilohms (kΩ), megohms (MΩ)
Key specs: Resistance value, power rating (usually 1/4W)
How to identify: Color bands (use color code chart)
Common values: 220Ω, 330Ω, 1kΩ, 10kΩ

Symbols:

This symbol is the most commonly used outside of the USA, and is what we will be using in this course:

This symbol is most often used in America:

Critical rule: Always use current-limiting resistor with LEDs!

Capacitor (Ceramic)

What it does: Stores electrical charge, filters noise, creates timing circuits
Measured in: Farads (F), microfarads (μF), nanofarads (nF), picofarads (pF)
Polarity: Non-polarized (can be inserted either way)
Common values: 100nF (0.1μF), 10μF, 100μF
Used for: Decoupling, debouncing, RC timing circuits
Symbol:

Capacitor (Electrolytic)

What it does: Same as ceramic, but higher capacitance values
Measured in: Microfarads (μF)
Polarity: YES - POLARIZED! Long lead = positive (+), short lead = negative (-)
Common values: 10μF, 100μF, 1000μF
Used for: Power supply filtering, timing circuits

The following four symbols (with the positive terminal marked) are all commonly used:

⚠️ Warning: Connect backwards and it can explode! Always check polarity.

Diode

What it does: Allows current flow in only one direction
Polarity: Cathode (marked with stripe) = negative, Anode = positive
Common type: 1N4148 (signal diode), 1N4007 (power diode)
Used for: Reset logic, protection, rectification
Forward voltage drop: ~0.7V
Symbol:

How to use: Current flows from anode to cathode (stripe side)

Active Components

LED (Light-Emitting Diode)

What it does: Emits light when current flows through it
Polarity: Long leg = Anode (+), Short leg = Cathode (-)
Forward voltage: ~2V (red), ~3V (blue/white)
Typical current: 20mA
Symbol:

⚠️ Critical: ALWAYS use a current-limiting resistor (typically 220Ω-330Ω with 5V)

Resistor calculation: R = (Vsupply - VLED) / 0.02A
Example: R = (5V - 2V) / 0.02A = 150Ω → use 220Ω

Push Button

What it does: Momentary switch that completes circuit when pressed
Pins: 4 pins - two pairs internally connected
Used for: Clock input, reset, user input
Symbol:

Note: Buttons "bounce" - they make/break contact multiple times. Needs debouncing!

Integrated Circuits (ICs)

Breadboard & DIP Package Basics

All ICs in this course use DIP (Dual In-line Package):

• Two parallel rows of pins
• Pin 1 marked with notch or dot
• Pins numbered counter-clockwise from Pin 1
• Always straddle the breadboard center gap

Standard pinout: Pin 1 (top-left) → Pin N (top-right) → Pin N+1 (bottom-right) → Pin 2N (bottom-left)

CD4026 - Decade Counter with 7-Segment Decoder

What it does: Counts 0-9 and directly drives 7-segment display
Package: 16-pin DIP
Power: Pin 16 = Vcc (+5V), Pin 8 = GND
Key pins:

• Pin 1: Clock input (rising edge triggers count)
• Pin 2: Carry out (goes high on 9→0 transition)
• Pin 15: Reset (active high - tie to GND for normal operation)
• Pins 3-11: Seven-segment outputs (a-g)

Pinout diagram:

Used in: Module 1 & 2 (Counters and Clocks)

555 Timer

What it does: Versatile timing IC - generates clock pulses, delays, oscillations
Package: 8-pin DIP
Power: Pin 8 = Vcc (+5V), Pin 1 = GND
Modes: Astable (oscillator), Monostable (one-shot), Bistable (flip-flop)

Key pins:

• Pin 2: Trigger (starts timing)
• Pin 3: Output
• Pin 4: Reset (tie to Vcc if not used)
• Pin 5: Control voltage (bypass to GND with 10nF cap)
• Pin 6: Threshold
• Pin 7: Discharge

Pinout diagram:

Astable mode (oscillator): Add resistors and capacitor to generate clock signal

Used in: Module 1 (Timing Circuits)

7448 - BCD to 7-Segment Decoder

What it does: Converts 4-bit binary (BCD) to 7-segment display format
Package: 16-pin DIP
Power: Pin 16 = Vcc (+5V), Pin 8 = GND
Inputs: Pins A, B, C, D (4-bit BCD input)
Outputs: 7-segment outputs a-g

Pinout diagram:

Used in: Module 3 (Decoders)

74181 - 4-bit ALU

What it does: Performs 16 arithmetic and 16 logic operations on 4-bit inputs
Package: 24-pin DIP
Power: Pin 24 = Vcc (+5V), Pin 12 = GND
Inputs: Two 4-bit operands (A and B), function select
Outputs: 4-bit result, carry, comparator outputs

Pinout diagram:

Used in: Module 5 (ALU Basics)

74283 - 4-bit Binary Full Adder

What it does: Adds two 4-bit binary numbers plus carry input
Package: 16-pin DIP
Power: Pin 16 = Vcc (+5V), Pin 8 = GND
Inputs: Two 4-bit numbers (A0-A3, B0-B3), Carry In
Outputs: 4-bit sum, Carry Out

Pinout diagram:

Used in: Module 5 (Calculators)

28C256 - 32KB EEPROM

What it does: Stores 32,768 bytes of data that persists without power
Package: 28-pin DIP
Power: Pin 28 = Vcc (+5V), Pin 14 = GND
Capacity: 32KB (256K bits)
Address lines: A0-A14 (15 address lines)
Data lines: D0-D7 (8-bit data)

Pinout diagram:

Used in: Module 4 & 7 (Memory and Lookup Tables)

Logic Gates (7400 series)

Common 7400 series chips:

• 7400: Quad 2-input NAND
• 7402: Quad 2-input NOR
• 7404: Hex Inverter (NOT)
• 7408: Quad 2-input AND
• 7432: Quad 2-input OR
• 7486: Quad 2-input XOR

Package: 14-pin DIP
Power: Pin 14 = Vcc (+5V), Pin 7 = GND

Displays

7-Segment Display (Common Cathode)

What it does: Displays digits 0-9 (and some letters)
Segments: 7 LEDs arranged in figure-8 pattern (a-g) + decimal point
Types:

• Common Cathode: All cathodes connected together → connect to GND
• Common Anode: All anodes connected together → connect to Vcc

Pinout and segment layout (common-cathode configuration)

⚠️ Important: Each segment needs current-limiting resistor (220Ω typical)

Used in: All Modules

Power & Tools

Breadboard

What it does: Temporary circuit prototyping without soldering
Power rails: Red (+) and Blue (-) lines run the full length
Component area: 5 holes connected vertically in each row
Center gap: For straddling ICs

Internal connections:

Pro tip: Test power rail continuity - some breadboards have breaks in the middle!

Jumper Wires

Types:

• Solid core: For breadboards (holds shape, doesn't bend easily)
• Stranded: For connections that move (more flexible)

Color coding (recommended):

• Red: Power (Vcc, +5V)
• Black: Ground (GND, 0V)
• Other colors: Signals

Sizes: Pre-cut or spool (strip and cut to length)

Power Supply

What you need: 5V DC regulated power supply
Options:

• Wall adapter (5V, 1A+)
• USB power bank (5V)
• Breadboard power supply module
• 4× AA batteries (6V - works but slightly high)

Connector: Match to breadboard power rails

Multimeter

Essential tool for debugging!

Modes you'll use:

• DC Voltage (V⎓): Measure Vcc, signal levels
• Continuity (♪): Test connections (beeps if connected)
• Resistance (Ω): Check resistor values

How to use:

• Black probe → COM (common/ground)
• Red probe → measurement point
• Select appropriate mode

Quick Reference Tables

IC Power Pins

Rule: ALWAYS connect power pins first!

Resistor Color Code

Common values:

• 220Ω: Red-Red-Brown (LED current limiting)
• 330Ω: Orange-Orange-Brown (LED current limiting)
• 1kΩ: Brown-Black-Red (pull-up/pull-down)
• 10kΩ: Brown-Black-Orange (pull-up/pull-down)

Capacitor Code Decoder

Ceramic capacitor markings:

• 104 = 10 × 10⁴ pF = 100,000pF = 100nF = 0.1μF
• 103 = 10 × 10³ pF = 10,000pF = 10nF = 0.01μF

Electrolytic: Usually marked directly (e.g., "100μF 16V")