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Diode
Passive parts

Diode

Two-terminal polarized semiconductor that conducts current in only one direction (anode → cathode). Common variants: standard rectifier (1N4001-1N4007 — up to 1A, 50-1000V), Schottky (1N5817/1N5819 — low forward drop ~0.3V, fast switching), small-signal (1N4148 — fast, low current), Zener (1N4733A 5.1V, 1N4737A 7.5V, etc. — used for voltage clamping/regulation). Used as a flyback diode across inductive loads (motors, relays, solenoids), as a reverse-polarity protector, in voltage rectification, and as an OR-ing diode in power-supply combining.

Pinout — Diode

Pin Signal Description
ANODE Positive terminal — conventional current flows in here
CATHODE Negative terminal — marked with the white stripe; current flows out here

Wiring notes

2-pin POLARIZED component. Use componentId diode and put the part number (and type if non-standard) in the label, e.g. '1N4007', '1N4148', '1N5819 Schottky', '1N4733A Zener 5.1V'. Pins: ANODE (+, conducts INTO this lead) and CATHODE (-, conducts OUT of this lead — marked with the white stripe on the body). Conventional current flows ANODE → CATHODE; the diode blocks reverse current. **Flyback / freewheel diode (motors, relays, solenoids):** CATHODE to V+ (the load's positive supply), ANODE to the switched node (transistor's drain/collector). The diode shorts out the back-EMF spike that the inductor produces when current is interrupted. **Reverse-polarity protection:** ANODE to V+ input, CATHODE to circuit V+ — drops ~0.7V (use a Schottky to drop only ~0.3V). **Zener for voltage clamping:** install REVERSE-biased (CATHODE to V+, ANODE to GND) — clamps the rail to the Zener voltage.

Example wiring diagram — Diode

From To Wire
board:D4 x1:ANODE green
x1:CATHODE board:GND black

Example Arduino code — Diode

This example was written and compile-checked for the arduino-uno. Codey Online adapts it to any other supported board for you.

// Diode example for Arduino Uno
// This sketch demonstrates a diode as a simple reverse-polarity / current-direction component.
// It drives D4 HIGH, so current can flow from D4 -> diode ANODE -> diode CATHODE -> GND.

const int diodePin = 4;

void setup() {
  pinMode(diodePin, OUTPUT);
  digitalWrite(diodePin, HIGH);

  Serial.begin(9600);
  Serial.println("Diode example started.");
  Serial.println("D4 is set HIGH so current can flow through the diode from ANODE to CATHODE.");
}

void loop() {
  // Keep the output HIGH continuously.
  // If you reverse the diode, it will block current flow.
  digitalWrite(diodePin, HIGH);
  delay(1000);
}

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