Cheap simple timer circuit clicks for days with one 9V battery

Mark Frauenfelder 10:08 pm Tue May 29, 2007

I love the way this simple 555 timer circuit looks. This fellow built one and shows you how to make one of your own. Fun!

I wanted to see how few parts I could use, from what I had on hand, to build this clicking blinking LED device based on a 555 chip.

The earphone clicks and the red LED blinks at a constant 137 times a minute. The exact rate depends on the value of the resistor and capacitor. That rate will be maintained very precisely for the life of the battery. It's not forever, but listening closely I could still hear the earphone faintly clicking after 6 days of continuous operation.

This device also simulates a faucet dripping. Hide it near a sink to frustrate a handyman.

(The current issue of MAKE (Vol 10) has a bunch of 555 timer projects, written by Charles Platt.)

Link

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