Lab 4 Hardware Foundations

Breadboards, LEDs, Resistors, Jumper Cables, and Pico Pins

CMPSC 100 Computational Expression

Hardware Foundations

Breadboards: The Circuit Playground

Breadboard Basics

  • Breadboards let you build circuits without soldering.
  • Power rails (red/blue lines) run vertically—each column is connected, but left and right rails are separate.
  • Middle rows connect horizontally—each row is split by the center gap.
  • Example: All holes in row 10 (left side) are connected; all holes in the first blue bus are connected, but not to the second blue bus.
  • Tip: Always double-check connections—misplaced wires are a common error!
  • First time using a breadboard? Push components in gently and make sure the legs are straight.

Pico 2 Pins

Refer to the pinout diagram to identify GPIO pins, power (3V3), and ground (GND).

LEDs: Light Emitting Diodes

LED Basics

  • LEDs only work in one direction!
  • Long leg = positive (anode), connects to HIGH voltage (3.3V or 5V).
  • Short leg = negative (cathode), connects to LOW voltage (GND).
  • Common mistake: LED facing the wrong way—always check leg orientation!
  • In Lab 4: Each LED is controlled by a GPIO pin on the Pico.
  • Tip: If your LED doesn’t light up, try flipping it around!

Resistors: Controlling Current

Resistor Basics

  • Resistors limit the flow of electrical current.
  • Color bands show resistance value (measured in ohms Ω).
  • Why use them? Protect LEDs from too much current—without a resistor, your LED can burn out!
  • Lower resistance = brighter LED. Higher resistance = dimmer LED.
  • Typical values: 220Ω (bright), 330Ω (safe and slightly dimmer).
  • Tip: Place the resistor in series with the LED—one leg in the same row as the LED anode, the other to the Pico pin.

Jumper Cables: Making Connections

  • Jumper cables are flexible wires for connecting components on the breadboard.
  • Male-to-male cables are most common for breadboards.
  • Use them to connect Pico pins to LEDs, resistors, and power rails.
  • Tip: Use different colors for clarity (e.g., red for power, black for ground) but colors do not affect functionality.
  • Push cables in firmly but gently—loose connections are a common source of problems.

Pico Pins and Power

  • Pico GPIO pins control LEDs and read sensors.
  • 3V3 (Power): Connects to the breadboard’s red power rail.
  • GND (Ground): Connects to the blue ground rail.
  • Pin numbers (e.g., 15, 14, 13) are used in your code to control LEDs.
  • Always disconnect USB before wiring! Prevents short circuits and protects your board.
  • Tip: Use the pinout diagram to find the correct pins for your circuit.

Common Mistakes and Troubleshooting

  • LED not lighting up?
    • Check orientation (long leg to power, short leg to ground).
    • Check connections—are all wires fully inserted?
    • Try a different GPIO pin in your code.
  • Multiple LEDs not working?
    • Check that all resistors are in place.
    • Make sure each LED has its own resistor.
    • Verify power and ground rails are connected to the Pico.
  • Breadboard confusion?
    • Remember: Power/ground rails are vertical, component rows are horizontal.
    • The center gap splits the board—components on one side aren’t connected to the other.

Quick Tips for Success

  • Double-check LED orientation (long leg to power, short leg to ground).
  • Use resistors for every LED—protect your hardware!
  • Keep wiring neat—use color-coded jumper cables.
  • Understand breadboard connections—vertical for power/ground, horizontal for components.
  • Refer to the Pico pinout diagram when connecting your circuit.
  • Test your circuit with test_LED.py before starting the full light show!