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Astable Multivibrator: Hairball Edition

Just to show all those precisely machined enclosures and tidy hand-wired boards don’t count for much:

Astable Multivibrator - as-built

Astable Multivibrator – as-built

The schematic again:

Astable Multivibrator - as-built - simulation

Astable Multivibrator – as-built – simulation

It started with that idea and evolved slightly.

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  1. #1 by rkward on 2014-10-28 - 08:02

    I’m confused. Where’s the 555? ;-)

    • #2 by Ed on 2014-10-28 - 08:21

      A guy I know built a wall-following robot with one transistor (none of this fancy microcontroller stuff for him), so the parts you see here could become a robot controller with redundancy

  2. #3 by smellsofbikes on 2014-10-28 - 11:55

    Okay, why D3 and D4? I’ve built this circuit many a time, but without them.

    • #4 by Ed on 2014-10-28 - 22:05

      The base-emitter junction breaks down at about 6 V reverse bias and there’s no current limiting through the caps when the collectors saturate; IIRC, they don’t quite reach breakdown with a 9 V battery, but the diodes may save some wear & tear.

      • #5 by smellsofbikes on 2014-10-29 - 17:53

        Makes sense. I’m working off 9V so I didn’t consider reverse bias too deeply.