Searching \ for 'Trying to get 32KHz crystal to spin up!' 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/io/serial/spis.htm?key=spi
Search entire site for: 'Trying to get 32KHz crystal to spin up!'.

Truncated match.
PICList Thread
'Trying to get 32KHz crystal to spin up!'
1997\07\07@125234 by Tom Coonan

picon face
Hello,

I'm working on my PIC "Power Manager" which is set up much like the circuit
shown in AN582, with a fast main crystal between OSC1 and OSC2, and then
the watch crystal between T1OSI and T1OSO.  This is a pretty neat thing
that the PIC can do - allowing a sleeping PIC to sleep, but continue to
keep time via the Timer1 and the 32KHz crystal.  I have much of my firmware
done.  The problem is - I can't get the 32KHz crystal to oscillate reliably.
My boards don't come in for another week, so, I'm prototyping on a vector
board.

I'm not an analog guru, but I've tried keeping the wires short, etc.  If I
lick my pinky and touch around the circuit (seriously...) I can get a few
hundred ticks into Timer1 but nothing sustained.

I have two 30pF caps across the crystal to ground.  I've tried some large value
resistors (e.g. 500K to 10M) across the crystal, and can often get
several dozen ticks.  No nets are greater than, say, 1/2 inch.

I'm surprised this is all *that* sensitive.  Am I doing something wrong?

Tom Coonan
spam_OUTThomas.CoonanTakeThisOuTspamSciatl.com
http://www.mindspring.com/~tcoonan

1997\07\08@022756 by Didier JEANJEAN

flavicon
face
Hi,

I don't know if you do somethink wrong, but in many times with prototype
board I have experience problem with quartz and timing. The better and
quicker solution I have find is to build a oscillator, without PIC (perhaps
with a 74HC4060), and then to connect the clock to the PIC (T1OSI).

Didier

----------
> From: Tom Coonan <.....tcoonanKILLspamspam@spam@MINDSPRING.COM>
> To: PICLISTspamKILLspamMITVMA.MIT.EDU
> Subject: Trying to get 32KHz crystal to spin up!
> Date: lundi 7 juillet 1997 19:52
>
> Hello,
>
> I'm working on my PIC "Power Manager" which is set up much like the
circuit
> shown in AN582, with a fast main crystal between OSC1 and OSC2, and then
> the watch crystal between T1OSI and T1OSO.  This is a pretty neat thing
> that the PIC can do - allowing a sleeping PIC to sleep, but continue to
> keep time via the Timer1 and the 32KHz crystal.  I have much of my
firmware
> done.  The problem is - I can't get the 32KHz crystal to oscillate
reliably.
> My boards don't come in for another week, so, I'm prototyping on a vector
> board.
>
> I'm not an analog guru, but I've tried keeping the wires short, etc.  If
I
> lick my pinky and touch around the circuit (seriously...) I can get a few
> hundred ticks into Timer1 but nothing sustained.
>
> I have two 30pF caps across the crystal to ground.  I've tried some large
value
> resistors (e.g. 500K to 10M) across the crystal, and can often get
> several dozen ticks.  No nets are greater than, say, 1/2 inch.
>
> I'm surprised this is all *that* sensitive.  Am I doing something wrong?
>
> Tom Coonan
> .....Thomas.CoonanKILLspamspam.....Sciatl.com
> http://www.mindspring.com/~tcoonan

1997\07\08@054528 by all (Stephen Birchall)

flavicon
face
I've often found that connecting the crystal can to ground will get an
oscillator to function

Steve

{Quote hidden}

1997\07\08@092118 by Joe Dowlen

flavicon
face
Get rid of the 30 pF capacitors. The normal loading on "watch" type crystals is 6 pF or 12.5 pF depending on what type you have. Your circuit will supply enough stray capacitance to properly load these crystals.

Joe

----------
From:   Stephen Birchall (Stephen Birchall)[SMTP:EraseMEN.S.Birchallspam_OUTspamTakeThisOuTLBORO.AC.UK]
Sent:   Tuesday, July 08, 1997 4:44 AM
To:     PICLISTspamspam_OUTMITVMA.MIT.EDU
Subject:        Re: Trying to get 32KHz crystal to spin up!

I've often found that connecting the crystal can to ground will get an
oscillator to function

Steve

{Quote hidden}

1997\07\09@071429 by Gary Sutcliffe
flavicon
face
At 12:52 PM 7/7/97 -0500, you wrote:
>Hello,
>
>I'm working on my PIC "Power Manager" which is set up much like the circuit
>shown in AN582, with a fast main crystal between OSC1 and OSC2, and then
>the watch crystal between T1OSI and T1OSO.  This is a pretty neat thing
>that the PIC can do - allowing a sleeping PIC to sleep, but continue to
>keep time via the Timer1 and the 32KHz crystal.  I have much of my firmware
>done.  The problem is - I can't get the 32KHz crystal to oscillate reliably.
>My boards don't come in for another week, so, I'm prototyping on a vector
>board.


Its probably not the problem with a vector board prototype, but I have had
trouble with board contamination with PICs with low frequency crystals.  The
problem was solved by carefully cleaning the area around the crystal with
alcohol.

Good luck!
- Gary

------------------------------------------------------------------------
Gary Sutcliffe,  W9XT          Unified Microsystems
@spam@ppvvppKILLspamspammixcom.com              PO Box 133 Slinger, WI 53086
http://www.qth.com/w9xt        414-644-9036

More... (looser matching)
- Last day of these posts
- In 1997 , 1998 only
- Today
- New search...