NicheCalcs

Example: Calculating Resistor Value for an LED

You want to connect a red LED to a 5V power supply. The LED has a forward voltage of 2V and operates safely at 20 mA. To prevent damage to the LED, a current-limiting resistor is needed in series.

Step 1: Use the Formula

The resistor value is calculated using Ohm's Law:

\[ R = \frac{V_s - V_f}{I} \]

Step 2: Plug in the Values

• Supply voltage: \( V_s = 5\;V \)
• LED forward voltage: \( V_f = 2\;V \)
• LED current: \( I = 20\;mA = 0.02\;A \)

Now compute:

\[ R = \frac{5\;V - 2\;V}{0.02\;A} = \frac{3}{0.02} = 150\;\Omega \]

Step 3: Use the Calculator

Enter these values into the calculator:

• Supply voltage: 5 V
• LED forward voltage: 2 V
• LED current: 20 mA

The calculator will return a recommended resistor value of 150 Ω.

Disclaimer: These calculators are provided for informational purposes only. Always verify your designs against relevant engineering standards and consult a qualified professional. We do not take responsibility for any errors or damages resulting from the use of these calculations.