Homebrew PCBs

FWIW, I've published some advice/opinions and tutorial information
on how to design your PCBs so that they're more easilly fabricated
in a homebrew/hobbyist context.  The tutorial is based on EAGLE, but
the principles should apply to other CAD packages as well.

http://www.instructables.com/ex/i/E8C98D522C771029BC6B001143E7E506/

BillW

Ok, I have a question about this page:
http://www.instructables.com/ex/i/532834782C781029BC6B001143E7E506/

I've never done this, been mainly using microprocessors so far.

How does it 'start'?  Which LED blinks first?  Is it a sort of lottery,
depending on which capacitor gets charged first?  I figure we are assuming
the capacitors won't be perfectly identical (due to tolerance range).

Both 'sides' of the circuit are identical, so I would assume matched
blinking rates (50% per side).  It's the 'first step' that always bothered
me with these kind of circuits, what happened RIGHT after you pushed ON?

The flip-flop stuff is another thing that I have serious trouble
understanding.

Robert
:)

> -----Message d'origine-----
> De : Homebrew_PCBs@yahoogroups.com 
> [mailto:Homebrew_PCBs@yahoogroups.com] De la part de Bill Westfield
> Envoyé : mai 4 2006 18:37
> À : Homebrew_PCBs@yahoogroups.com
> Objet : [Homebrew_PCBs] Design rules for hobbyist PCBs...
> 
> 
> FWIW, I've published some advice/opinions and tutorial 
> information on how to design your PCBs so that they're more 
> easilly fabricated in a homebrew/hobbyist context.  The 
> tutorial is based on EAGLE, but the principles should apply 
> to other CAD packages as well.
> 
> http://www.instructables.com/ex/i/E8C98D522C771029BC6B001143E7E506/
> 
> BillW
>

On Fri, 05 May 2006 01:10:27 +0200, Robert Hedan  
<robert.hedan@...> wrote:

> Ok, I have a question about this page:
>
> http://www.instructables.com/ex/i/532834782C781029BC6B001143E7E506/
>
>
> I've never done this, been mainly using microprocessors so far.
>
>
> How does it 'start'?  Which LED blinks first?  Is it a sort of lottery,
>
> depending on which capacitor gets charged first?  I figure we are  
> assuming
>
> the capacitors won't be perfectly identical (due to tolerance range).
>
>
> Both 'sides' of the circuit are identical, so I would assume matched
>
> blinking rates (50% per side).  It's the 'first step' that always  
> bothered
>
> me with these kind of circuits, what happened RIGHT after you pushed ON?
>
>
> The flip-flop stuff is another thing that I have serious trouble
>
> understanding.
>
>
> Robert


The books usually say "imbalances in components" i think.
If you believe in god, why not give the guy some credit?

I had to force a default position to go on all the time in a similar  
circuit once, it wasn't as easy as one would have hoped. Using larger caps  
in one place did not work. But it was different to your multivibrator, i  
think here they would.

ST

Stefan Trethan wrote:

>
>The books usually say "imbalances in components" i think.
>If you believe in god, why not give the guy some credit?
>
>  
>
  Supreme Being or just math?  Calculate the number of electrons needed 
to switch, the length of time, and the odds of both reaching their 
number at exactly the same time, and there are likely less particles in 
the universe than the length of those odds in a decent circuit..  Of 
course there's really a threshold after which it will switch on but 
hasn't yet, so the timing won't need to be as precise, but likely still 
in the astronomically rare region.  And a lot of these type circuits are 
poorly designed, by bad design making it far more likely to have a 
match, although usually still very rare.  Didn't really look at it but 
this one looks to basic to be messed up too much though..

LOFL ran into this looking for the 50 eyes proves God thing to poke 
holes at the technical inaccuracies a while back.  Had favorites early 
on but too many are too funny to pick from..
http://www.godlessgeeks.com/LINKS/GodProof.htm

Alan