AddOhms #8: LEDs and Current Limiting Resistors

The idea for AddOhms #8 has been around for quite some time.  I’m always trying to find ways to explain why current limiting resistors are necessary.  So while working in the shop one day, I decided to play with some LEDs and a bench-power supply.  Then I decided to record what happens.


In fact, I shot all the lab video used here one day.  Then about 3 weeks later, I got around to writing the script for this tutorial.   Since the two were disconnected, you’ll probably notice a couple of jump cuts in the live action footage.

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2 thoughts on “AddOhms #8: LEDs and Current Limiting Resistors

  1. Love your site and videos! Great Job… I enjoy LEDs and have used pre designed LED strips, lights, etc for some time. I found a particular wavelength LED I want to use and find I am burning them out! most likely due to direct battery connection and over current supply to the LED, so your video is very helpful…BUT, I recall somewhere on your sites you described most LEDs are designed to operate up to 2 volts above the ‘vf??? That didn’t seem right to me but I set up some lights designed for Vf of 1.9-2.3 on AA batts, running about 2.7 volts and thought that would be ok…funny thing very bright!! and lasted about 5 hours…so your current explanation must the the cause. But how do small LED flashlights I see and have taken apart have AA or AAA batts driving LEDs, but with no resistors?? That’s my question…Thanks for your site…