Very Very Simple Blinker LED

Thread Starter


Joined Nov 27, 2007
Hey all - Is it possible to build a blinking LED circuit using only capacitors and resistors? Would diodes help, I pulled some out of a TV but don't know their values...?


Joined Jul 17, 2007
The short answer: no, unless the flasher is built into the LED itself.

Slightly longer answer: you need some kind of valve or semiconductor to sense when the voltage across the RC network has exceeded a certain threshold level, determined by the designer of the circuit. The valve or semiconductor then turns on the LED while draining the voltage from the RC network, until it has fallen below another threshold level.

As mentioned in the short answer, there ARE self-flashing LED's. These have a timer circuit and current-limiting features built in. You can actually use them to flash a pretty long string of LED's.


Joined Jun 30, 2006
For use with scrap parts and two npn transistors, use a meter to figure out which parts will work. Learn how to read capacitors or get a meter that will read them.

Simplest two I've seen that work with 1.5v
Lasts six months

Vampires that cell
Lasts 12 months

LM3909 is obsolete and hard to get but the others circuits are cool.