[sdiy] strange sequencer behavior

[Sven Windisch]

On Mon, 26 May 2003, Peter Grenader wrote:

hi peter.

> 2) If it's breadboarded, check where the wires coming from and going to the
> main counter directly are routed.  In the future, make these leads as short
> as possible.  But if that's impossible now,  Make sure they aren't laying
> over anything that may radiating to the counter.


uhm, yeah. it's breadboarded. and, well... its a really big mountain of
wires floating around on the board. i tried to make them as short as
possible but they're probably still too long.

> 3) Look at the isolated wires on a scope.  If yours doesn't go into the high
> megahertz range, make the horizontal sweep stationary and turn up the
> brightness.  You will probably see dots appearing, indicating a change of
> logic state, when you don't want it.  This is either noise - or it's very
> possible you've got blown CMOS.

well, i don't have a scope. i blew up the 74HC85 an wondered why it did'nt
work at all, so i changed it and now it works as described above. it's
sure possible i blew up the 4024 too. this will be the next thing i try.

> 4)  How is your clock and reset signals conditioned?  Are you intentionally
> controlling their on-time?  If not, you should.  Even though most counters
> respond to the high-rising side of the incoming clock, having them stay that
> way any longer than required could be sending your counter misinformation
> that it's responding to.  I put all of my incoming clock signals going to
> the 4516 (all accept hold) through an r/c at the base of a tranny which was
> then routed through a CMOS inverter before going into the counter.  I was
> having a world of problems before i did this.

uhm, all signals are routed directly from chip to chip with no parts
between in. maybe thats the problem. at least, i did it like its done in
the schematic i mentioned. (did i mention it? anyway:
http://machines.hyperreal.org/categories/DIY/sequencer/analogue.sequencer.gif)

greetings,
sven.

-- 
To some ears, "computational philosophy of science" will
sound like the most self-contradictory enterprise in
philosophy since business ethics.
[Paul Thagard in "Computational Philosophy of Science"]