Archive for August 27th, 2013

Soldering Project: Astable Multivibrator

We’ve been kicking around ideas for introductory soldering / electronics projects at Squidwrench, which prompted me to come up with a classic astable multivibrator circuit:

Astable Multivibrator - simulation

Astable Multivibrator – simulation

Everything is totally non-critical: it should oscillate as long as the base resistors are small enough to lightly saturate the transistors. The LEDs let you know it’s actually working.

You’d probably want a few decades of caps and a decade’s worth of resistors on pin headers, so as to cover the range from visible blinkiness to nasty audio squeal.

The pulse generator and cap at the bottom apply a jolt at T=0 to knock the circuit off balance. Otherwise, the simulation will just sit there and do nothing; in the real world, of course, nothing stays balanced for very long.