Re: gEDA-user: SMD soldering challenge status

[DJ Delorie <dj@xxxxxxxxxxx>]

> > By showing phase instead of actual clocking, we avoid the need to
> > have <60Hz frequencies.  The LEDs would show the beat between them
> > due to component tolerances, not the actual clocks.
> 
>    Now THAT is a fun idea!

Ok, I prototyped this (yay radio shack electronics labs :) with two
0.01u/100k oscillators, each buffered, using up the hex inverter.  The
outputs went to D and C of the D flip flop, resulting in the
oscillators changing too fast for the eye to see but the FF changing
about 2-3 times a second.

The prototype didn't use the extra inverters or transistors (i.e. all
the SOT-* parts), but I can just chain those through the output to
drive the 0603 LEDs.  If we have a SOT-323-5 inverter, do we need a
SOT-323 transistor?  I don't think it would add anything to the
challenge, and it's eight cents more to play with.

If we can fit this on a single sided Olimex board, we're at $1.99 per
board.  If we need double sided, we can drop the SOT-23 (the biggest
transistor) to stay in budget.  I haven't tried to lay out the circuit
in the 16x10mm space.

Of course, the prototype was with 4000 series CMOS, not the schmidt
triggered 74LVC inverters.


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