Searching \ for 'LP XTAL' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/timers.htm?key=xtal
Search entire site for: 'LP XTAL'.

Truncated match.
PICList Thread
'LP XTAL'
2000\03\29@215338 by John Orhan

flavicon
face
Hi all,

I have a problem regarding the LP (low frequency Xtal) setting. I have tried
to run the PIC (F84) with a 35Khz Xtal ratted from an old cheap digital
watch. For some reason it isn't working. I have 33pF cap's on it and it
seems that when I load it up with a CRO lead, or even just touch it, the
oscillator winds up and kicks into life. Is 33pF too small for the lower
frequency?? Anyone know how this animal works?

                                       Sincerely       John

2000\03\29@232522 by Robert Rolf

picon face
John Orhan wrote:
> I have a problem regarding the LP (low frequency Xtal) setting. I have tried
> to run the PIC (F84) with a 35Khz Xtal ratted from an old cheap digital
> watch. For some reason it isn't working. I have 33pF cap's on it and it
> seems that when I load it up with a CRO lead, or even just touch it, the
> oscillator winds up and kicks into life. Is 33pF too small for the lower
> frequency?? Anyone know how this animal works?

See the section on 'Crystal/Ceramic resonator operation' in the
databook. You need to add a small series resistance to OCS2  to create
noise. "2: A series resistor (RS) may be required for AT strip cut
crystals". AFAIK 32khz crystals are strip cut. AT refers to the crystal
axis used for that cut (just as XT refers to that axis).
The various axis of a crystal have different properties (tempco,
stability, etc.) and so a crystal is not -just- a crystal, you have
to get one that is cut to match your application.



--
Robert.Rolf-AT-UAlberta.ca

2000\03\30@005345 by John Orhan

flavicon
face
Hi Robert,
Thanks for your tip.
                               John

               -----Original Message-----
               From:   Robert Rolf [spam_OUTRobert.RolfTakeThisOuTspamUALBERTA.CA]
               Sent:   Thursday, 30 March 2000 2:23
               To:     .....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU
               Subject:        Re: LP XTAL

               John Orhan wrote:
               > I have a problem regarding the LP (low frequency Xtal)
setting. I have tried
               > to run the PIC (F84) with a 35Khz Xtal ratted from an old
cheap digital
               > watch. For some reason it isn't working. I have 33pF cap's
on it and it
               > seems that when I load it up with a CRO lead, or even just
touch it, the
               > oscillator winds up and kicks into life. Is 33pF too small
for the lower
               > frequency?? Anyone know how this animal works?

               See the section on 'Crystal/Ceramic resonator operation' in
the
               databook. You need to add a small series resistance to OCS2
to create
               noise. "2: A series resistor (RS) may be required for AT
strip cut
               crystals". AFAIK 32khz crystals are strip cut. AT refers to
the crystal
               axis used for that cut (just as XT refers to that axis).
               The various axis of a crystal have different properties
(tempco,
               stability, etc.) and so a crystal is not -just- a crystal,
you have
               to get one that is cut to match your application.



               --
               Robert.Rolf-AT-UAlberta.ca

2000\03\31@110310 by M. Adam Davis

flavicon
face
Also on the PIC data sheets you'll note the oscillator selection, LP with a
32KHz crystal needs about 68-100pf caps.

I'm running mine now with 100pf, no series resistance, and everything is fine.

-Adam

John Orhan wrote:
{Quote hidden}

More... (looser matching)
- Last day of these posts
- In 2000 , 2001 only
- Today
- New search...