74HC165 noise
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Posts: 46,084
Hello again,
I'm doing some work with the 74HC165, have used it one time before and worked
xlnt. This time I set up a test on a bin board and on a PCB but am getting
noise. It will show correct number, but also either 255 or 0 at intervals in
addition to other 8 bit style numbers. I have all the inputs to +5 with a 10k
resistor. I even tried adding pulls ups to all the other pins including the
lines going to stamp. It occurs whether I am using inverted or regular
output. I am using NTE 74HC165 chips.
Anyone else ever have similar problems?
Once thanks in advance,
OP
[noparse][[/noparse]Non-text portions of this message have been removed]
I'm doing some work with the 74HC165, have used it one time before and worked
xlnt. This time I set up a test on a bin board and on a PCB but am getting
noise. It will show correct number, but also either 255 or 0 at intervals in
addition to other 8 bit style numbers. I have all the inputs to +5 with a 10k
resistor. I even tried adding pulls ups to all the other pins including the
lines going to stamp. It occurs whether I am using inverted or regular
output. I am using NTE 74HC165 chips.
Anyone else ever have similar problems?
Once thanks in advance,
OP
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
the IC?
> From: electronguy@a...
> Reply-To: basicstamps@yahoogroups.com
> Date: Tue, 17 Sep 2002 22:00:26 EDT
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] 74HC165 noise
>
> Hello again,
>
> I'm doing some work with the 74HC165, have used it one time before and worked
> xlnt. This time I set up a test on a bin board and on a PCB but am getting
> noise. It will show correct number, but also either 255 or 0 at intervals in
> addition to other 8 bit style numbers. I have all the inputs to +5 with a 10k
> resistor. I even tried adding pulls ups to all the other pins including the
> lines going to stamp. It occurs whether I am using inverted or regular
> output. I am using NTE 74HC165 chips.
> Anyone else ever have similar problems?
>
> Once thanks in advance,
> OP
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
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>
Yes, I actually went and soldered a .1uf multilayer ceramic cap to the VCC
and VSS pins across the top of the chip. It helped a bit, but I still get
about 25-50% 0 with the occasional 255 showing up. Is it possible these chips
are more susceptible to noise vs. other brands of chip? I'm running out of
ideas and starting to clutch at straws. I swapped several 74hc165's as well
as swapped the stamp itself.
I have a powersupply using an LM338 to supply the 5vdc.
In a message dated 9/17/02 9:56:10 PM Pacific Daylight Time,
ben@l... writes:
> Have you got a 0.1uF decoupling capacitor across the supply rails next to
> the IC?
>
>
> > From: electronguy@a...
> > Reply-To: basicstamps@yahoogroups.com
> > Date: Tue, 17 Sep 2002 22:00:26 EDT
> > To: basicstamps@yahoogroups.com
> > Subject: [noparse][[/noparse]basicstamps] 74HC165 noise
> >
> > Hello again,
> >
> > I'm doing some work with the 74HC165, have used it one time before and
> worked
> > xlnt. This time I set up a test on a bin board and on a PCB but am
> getting
> > noise. It will show correct number, but also either 255 or 0 at intervals
> in
> > addition to other 8 bit style numbers. I have all the inputs to +5 with a
> 10k
> > resistor. I even tried adding pulls ups to all the other pins including
> the
> > lines going to stamp. It occurs whether I am using inverted or regular
> > output. I am using NTE 74HC165 chips.
> > Anyone else ever have similar problems?
> >
> > Once thanks in advance,
> > OP
>
[noparse][[/noparse]Non-text portions of this message have been removed]