Electronics

My simplified electronics cheat sheet.

• Top boards must face away from the Raspberry Pi. I don't like RPi hats because they block air flow to the CPU.

• Solder on only one side of board; use the other side for the components

• Wiring colors:

  • White = ground

  • Black = power

  • Yellow, Red and Blue = GPIO pins

• Raspberry Pi GPIO pins have built in resistors - all GPIO pins REQUIRE diode or resistor

  • GPIO input should not exceed 3.3v. Use 1A, 3.3V zener diode to protect a GPIO pin from overload

  • RPi's GPIO pin -+- cathode of zener diode -- ground. The + is the input to the GPIO pin

  • Place a diode between GPIO output pin and circuit

Calculations:

• Ohm's Law: V = I x R (voltage = current * resistance)

  • Use Ohm's Law to calculate everything

  • Resistors

    • in series

      • (2) R = (r1 x r2) / (r1 + r2)

      • (3 or more): R = r1 + r2 + r3

    • in parallel: R = 1 / ( 1/r1 + 1/r2 +1/r3)

  • Capacitors

    • in series

      • (2) C = (c1 x c2) / (c1 + c2)

      • (3 or more) C = 1 / ( 1/c1 + 1/c2 +1/c3)

    • in parallel

      • C = c1 + c2 + c3

• Power = V x I = I**2 x R

Components:

• Resistors (reduce amount of current) - non-directional

  • Color band to resistor value calculator

• Diodes (prevent current flowing in wrong direction)

• Capacitors

• Transistors (emitter, base collector)

Wire: 20 or 22 gauge

Basic Circuits:

• Voltage divider: GND -- r1 -- Vout -- r2 -- Vin

  • r1 / (r1+r2) x Vin = Vout