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Make a simple LED circuit on a breadboard. (Maths included)

Build a one-LED circuit on a breadboard and use Ohm's law to pick the right resistor, with the maths worked through step by step.

Violet Pixels Updated 12 September 2026 2 min read

LED Breadboard Circuit

To create a simple LED circuit on a breadboard, you’ll need a few basic components: an LED, a resistor, a power source (like a battery or a bench power supply), and jumper wires. Let’s go through the process step by step, including the maths for selecting the correct resistor.

Components:

  1. LED (Light Emitting Diode)
  2. Resistor
  3. Power Source (e.g., a 9V battery)
  4. Breadboard
  5. Jumper Wires

Steps to Create the Circuit:

  1. Insert the LED into the Breadboard: LEDs have two legs, a longer one (anode) and a shorter one (cathode). Insert the LED into the breadboard, ensuring the legs are in different rows.
  2. Connect the Resistor: Attach one end of the resistor to the anode (longer leg) of the LED.
  3. Connect to Power Source: Use jumper wires to connect the free end of the resistor to the positive terminal of the battery and the cathode of the LED (shorter leg) to the negative terminal.

Maths for Selecting the Resistor:

The key formula here is Ohm’s Law:

V = I R where V is the voltage, I is the current and R is the resistance.

Steps:

  1. Determine the Forward Voltage (Vf) of the LED: This is typically found in the LED’s datasheet. Let’s assume Vf = 2 V.
  2. Determine the Desired Current (I): LEDs typically operate around 10-20mA. Assuming 20mA, which is I = 20 mA = 0.02 A.
  3. Calculate the Supply Voltage (Vs): This is the voltage of your power source, say a 9V battery.
  4. Calculate the Required Resistance (R) using the formula:
    R = (Vs - Vf) / I

Typical datasheet for an LED

Example Calculation:

Given Vs = 9 V, Vf = 2 V and I = 0.02 A:

R = (Vs - Vf) / I = (9 V - 2 V) / 0.02 A = 7 V / 0.02 A = 350 ohm

So, you’d need a resistor of approximately 350 ohms. It’s common to use the nearest standard resistor value, which in this case might be 330 ohms.

Additional Tips:

  • Always check the datasheet of your LED for the exact forward voltage and current ratings.
  • It’s better to err on the side of a slightly higher resistance to prevent burning out the LED.

With these steps and calculations, you can confidently set up a simple LED circuit on a breadboard. Remember, experimenting is key in electronics, so don’t hesitate to try different configurations and see what works best for your needs.