Electronics: Pulsing/Breathing LED

A few months ago I was looking to create a “pulsing LED” effect. What I was using this for was for a Halloween effect where I was placing a series of different colored ultra-bright LED’s under some beakers filled with water and dry ice, creating the Mad Scientists lab. One of my stated goals was to do this without using a microcontroller since I hadn’t gotten into microcontrollers yets.

I ended up using this project: http://www.rabidhardware.net/index.php?id=5

This essentially makes a scewed triangle wave, where the rise time is quicker than the fall time, creating a “breathing” effect.

There are a couple of other circuits that do similar things:

http://www.instructables.com/id/How_to_blinkbreathing_style_LED_while_you_are_p/

http://www.cpemma.co.uk/throbber.html

Of course, making a variable duty cycle PWM program with a microcontroller might end up better next time since I can control more LED’s with less.