IanW wrote:
"John Fields" wrote in message
...
On Thu, 06 Nov 2008 15:45:43 -0600, John Fields
wrote:


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A "gotcha" I noticed yesterday, or the day before is that, wired the way
it's shown, (with the register outputs sinking current) if all the
register outputs come up reset on power-on, then there won't be enough
current to turn on all the LEDs and you'll have to wait for an entire
cycle before the thing starts to chase properly. If you've got the pot
set to "full slow" that could take about 30 seconds, so it might be
working, but since nothing was appearing to happen it looked like it
wasn't working.

In order have it start right away the shift register outputs should
_source_ current, so I fixed the circuit and attached a copy of the new
schematic.
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Dotting the 'i's and crossing the 't's yields rev b:

I'm struggling to spot the difference between rev A & this one but I've got
a new breadboard together with REV A but it still doesn't work. No lights up
at all. Here's a pic of the circuit. I know you wont be able to tell much
but just in case!

I do not see any power or ground connections to the ICs. The 74HC194s should
have ground on pin 8 and Vcc on pin 16. The 74HC00 should have ground on pin 7
and Vcc on pin 14.