How To Power A LED

Published
<h3>How To Power A LED</h3>

Powering an LED is not as easy as simply hooking it up to a battery. An LED has almost no internal resistance. Therefore, if you hook it up directly to a battery, it will burn out quickly as the current flows unimpeded through the LED. You must add a resistor to the LED circuit. This tutorial explains how to calculate the resistance needed.

Step 1

In order to calculate the resistance needed, Ohm’s Law is used. Ohm’s Law can be stated as V = I x R, where V is voltage, I is current and R is resistance. Since we are calculating resistance, we can rearrange the formula to read R = V ÷ I.



Step 2

Plug the values you have into the formula. Performing the calculation will give you the value of the necessary resistor.

Step 3

For example, suppose you have a 12 V supply, a white LED with a forward voltage of 3.4 V, and a current of 20 milliamps (0.020 amps.) First calculate the voltage by subtracting 3.4 from 12, giving 8.6.

Step 4

Now calculate the following: R = 8.6 ÷ 0.020, or 430 Ω (ohms.)

Things Needed

  • The voltage of the battery to which you are connecting the LED
  • The current to be passed through the LED
  • The forward voltage of the LED (found on the LED’s data sheet)

TL;DR (Too Long; Didn’t Read)

If you are connecting LEDs in series, simply add the forward voltages together before subtracting from the supply voltage.



Dave Pennells

By Dave Pennells

Dave Pennells, MS, has contributed his expertise as a career consultant and training specialist across various fields for over 15 years. At City University of Seattle, he offers personal career counseling and conducts workshops focused on practical job search techniques, resume creation, and interview skills. With a Master of Science in Counseling, Pennells specializes in career consulting, conducting career assessments, guiding career transitions, and providing outplacement services. Her professional experience spans multiple sectors, including banking, retail, airlines, non-profit organizations, and the aerospace industry. Additionally, since 2001, he has been actively involved with the Career Development Association of Australia.