Resistor Collection 10Pcs

Learn the colour bands

The coloured bands on a resistor tell you its value. Choose a common value to see its bands and what it is used for.

Specifications

What you can build

Almost every circuit needs a resistor.

Pick the right LED resistor

Use Ohm’s law to find the resistor for any LED:

R = (supply voltage − LED voltage) ÷ current

For example, with a 5V Arduino pin, a red LED that drops about 2V, and 15 mA of current: (5 − 2) ÷ 0.015 = 200 Ω. Choose the next standard value up, which is 220 Ω.

Basic Arduino code: LED with a button

Wire an LED with a 220 Ω resistor to pin 9, and a push button between 5V and pin 2, with a 10 kΩ resistor from pin 2 to GND (the pull-down). The LED lights while you press the button.

const int buttonPin = 2;
const int ledPin = 9;
void setup() {
  pinMode(buttonPin, INPUT);   // 10k pull-down holds it LOW
  pinMode(ledPin, OUTPUT);
}
void loop() {
  digitalWrite(ledPin, digitalRead(buttonPin));
}

Basic Arduino code: voltage divider

Connect two 10 kΩ resistors in series between 5V and GND, and connect the middle point to A0. The output is half the input voltage: Vout = Vin × R2 ÷ (R1 + R2).

void setup() {
  Serial.begin(9600);
}
void loop() {
  int raw = analogRead(A0);
  float volts = raw * 5.0 / 1023.0;
  Serial.print("Voltage: ");
  Serial.println(volts);  // about 2.5 V with two 10k resistors
  delay(500);
}

Check the power: most resistors here are 1/4 W. If your circuit pushes more than 0.25 W through a resistor, choose the 0.5 W or 1 W options, or a higher value. Power = voltage × current.

Questions buyers ask