The Occupy Mars Learning Adventure

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How to use resistor and LED’s on Mars?

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CHOOSING THE RESISTOR TO USE WITH LEDS

Introduction: Choosing the Resistor to Use With LEDs

Picture of Choosing the Resistor to Use With LEDs
About: Creative swashbuckler. Writer for MAKE Magazine, presenter of inventions on TV, radio, magazines and newspapers. Professional problem solver. Annoyingly curious. Hacker of all things from computers to clot…
This question gets asked every day in Answers and the Forums: What resistor do I use with my LEDs? So I’ve put together several different ways to figure it out.

Lets get right to it:
Each of the steps do the same thing. Step 1 is the simplest and we go downhill from there.

No mater what way you choose you must first know these three things:

    • Supply voltage This is how much power you’re putting into the circuit. Batteries and wall warts will have the output voltage printed on them somewhere. If you’re using multiple batteries*, add the voltage together.
    • LED Voltage Sometimes “Forward Voltage” but usually just abbreviated “V”.
    • LED Current Sometimes “Forward Current”. This is listed in milliamps or “mA”.

Both of these last two can be found on the packaging for your LEDs or on your supplier’s web site. If they list a range (“20-30mA”) pick a value in the middle (25 in this case). Here are some typical values, but use your own values to be sure you don’t burn out your LEDs!:

Red LED: 2V 15mA
Green LED: 2.1V 20mA
Blue LED: 3.2V 25mA
While LED: 3.2V 25mA

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Author: Kids Talk Radio

Bob Barboza is an educator, STEM journalist, software designer and founder of The Occupy Mars Learning Adventures and the Barboza Design and Space Centers. He leads a team of scientists, engineers and STEAM++ educators. They are training students to become Jr. astronauts, scientists and engineers. His team provides internships and workshops in STEAM++ and the integration of Common Core State Standards and Next Generations Science Standards. Contact information: Bob.Barboza@Gmail.com

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