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Electronic components: resistor, capacitor, diode, LED and transistor

Properties1
tagsglossar, elektronik, grundlagen

2 min read

Electronic components: resistor, capacitor, diode, LED and transistor

In short: Resistors limit current, capacitors store charge, diodes pass current in only one direction, LEDs light up, transistors switch and amplify: the building blocks of every circuit.

In more detail: Processors also consist of billions of transistors. Knowing the simple components helps understanding schematics, power supplies and controller boards.

In Depth

Resistor and potentiometer

  • Fixed resistor: value via colour bands (e.g. brown-black-red = 1 kΩ) or SMD code; E12 series (10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82).
  • Uses: LED series resistor, pull-up/pull-down (define an input), voltage divider.
  • Mind power rating (¼ W, 1 W…).
  • Potentiometer: adjustable resistor (volume), photoresistor (LDR), thermistor (NTC).

Capacitor

Stores charge (unit farad, mostly µF/nF/pF). Tasks: smoothing (power supply), decoupling (100 nF right at ICs), filters, timing circuits. An electrolytic capacitor has polarity (minus stripe) and a voltage rating; wrong way round/overloaded it can burst. Old electrolytics dry out: a typical fault in power supplies and older consoles (failure, hum). Ceramic (MLCC) for high frequency. Charged capacitors can hold dangerous voltage.

Diode, LED, rectifier

  • Diode: current only anode → cathode (stripe = cathode); forward voltage ≈ 0.7 V (silicon), 0.3 V (Schottky).
  • Rectifier: converts AC to DC (bridge of 4 diodes).
  • Zener diode: stabilises voltage in reverse direction.
  • Flyback diode: protects against voltage spikes at relays/motors.
  • LED: diode with light; always a series resistor; long leg = anode; colour determines voltage (red ≈ 2 V, blue/white ≈ 3 V). WS2812/NeoPixel: LEDs with controller.

Transistor, MOSFET, IC

  • Transistor (BJT, MOSFET): electronic switch/amplifier; a small control current/voltage switches a large load (e.g. LED strip, motor, relay). N-channel MOSFET as low-side switch, drive the gate via a resistor.
  • Relay: mechanical switch (isolates mains galvanically; caution).
  • ICs: logic gates, operational amplifiers, microcontrollers, voltage regulators (7805 → 5 V, LDO), 555 timer.
  • Fuse, varistor, coil (inductance), crystal (clock).
  • Read the datasheet: pinout, limits (absolute maximum ratings).

See also: Electronics basics, Arduino and microcontrollers

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