74HC165 noise (solved and good advice for anyone)
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Posts: 46,084
Well after spending many hours trying to figure out what is wrong I
accidentily discovered it. I found out that if I put a little pressure on the
74HC165 it worked flawlessly, turns out I was getting some bad contact in my
bread board, electronically it was working fine, but the contacts were bad
enough just to cause some noise. This will not be an issue in my PCB. So if
you can't figure out why you get weird results in your prototype remeber to
check if its your bread board.
In a message dated 9/18/02 4:43:41 PM Pacific Daylight Time,
electronguy@a... writes:
>
> Hi,
>
> 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]
>
>
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>
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>
>
>
[noparse][[/noparse]Non-text portions of this message have been removed]
accidentily discovered it. I found out that if I put a little pressure on the
74HC165 it worked flawlessly, turns out I was getting some bad contact in my
bread board, electronically it was working fine, but the contacts were bad
enough just to cause some noise. This will not be an issue in my PCB. So if
you can't figure out why you get weird results in your prototype remeber to
check if its your bread board.
In a message dated 9/18/02 4:43:41 PM Pacific Daylight Time,
electronguy@a... writes:
>
> Hi,
>
> 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]
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
[noparse][[/noparse]Non-text portions of this message have been removed]