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• Final Revision

  Mark • 06/17/2016 at 17:49 • 0 comments

  My breadboard experiments seemed to suggest that it's OK to leave pin 5 of the venerable NE555 floating but it really isn't. The circuit becomes a bit too unstable that way. So I fixed it by adding a 0.01uF cap between pin 5 and GND. I've revised the schematic and PCB layout in the image gallery

• Building

  Mark • 06/14/2016 at 18:19 • 0 comments

  First attempt at building this module has failed... the first PCB layout was a bit too cramped and i messed it up. Back to the drawing board!

  Second attempt: another failure. The revised layout still contained a huge wiring error but after fixing that, i'm still not getting any oscillation. So frustrating! Did i damage the 555? Very probably, because now it doesn't do a thing in a breadboard setup either.

  Ordered some new 555 chips and various other bits and they've arrived today. I will start off on the breadboard again and carefully re-evaluate my PCB design effort before i continue. Fingers crossed I'll get things working this time.

  Oops! I seriously messed up the PCB design and made some incorrect connections ( pin 2 goes to pin 6 and not 5!). Fortunately, the original 555 chip survived my blunders so now i've got a few spares in my parts drawer. All is well that ends well?

  Anyway, I've found an even simpler version of the schematic and am using that as the basis for a new board design. To be continued...

  Third time lucky! I tried my hardest to mess it all up again with my limited soldering skills but I've managed to turn the revised board layout into a functional LFO module. The resistors and capacitor I've picked produce a frequency range from approx. 0.3 Hz to 32 Hz. That's about perfect for clocking sequencers and the like.

  Thinking about adding a slower LFO with squarewave and sawtooth outputs that would be more suitable for pitch or filter modulation.
  

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