timing and crystals
Archiver
Posts: 46,084
At 10/20/2000 +0000 08:41 AM, you wrote:
>hello all,
>
>Got something strange. I use a pcf 8583 timer (clock ic), that has a osci
>and osco pin. (Oscillator in, and oscillator out). According specification a
>32,768khz crystal must be pleased between these two pins, and a cap must be
>places between osci and Vdd.
They appear to require a fixed cap. (method 1) or a small trimmer cap
(method 2) between OscI and Vdd. - which method did you use, and what value
are you using ?
>My timer works fine, but much to slow. Tried a lot, nothing makes my timer
>runs faster.
>
>What is strange is the following. I can remove the cap, then it still works.
>I can remove the crystal, then it still works!! The timer keeps running but
>much to slow.
The cap. is apparently only an ancillary part, and is not required for
operation. Its presence is merely for ADJUSTING the time accurately. Much
depends on the tolerance and accuracy of your crystal oscillator. I'd check
that first. It may not be possible to firmly adjust a crystal with poor
tolerance features (IF that is the case). Many factors (ambient and other)
will effect the preformance of the crystal as well.
>The only way it runs faster is if i move my hand near the osci and osco pins
>of the chip, then a sort of interference seems to exist.
The natural capacitance of your body, and/or the heat from your hand can be
coming into play.
>can anybody help me out?
That's the best I can do, but I'm sure the Radio Amateurs, and more
technically minded folks may have other suggestions.
>thanks a lot in advance Pieter-Jan
Sure
Regards,
Bruce Bates
>_________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
>
>Share information about yourself, create your own public profile at
>http://profiles.msn.com.
>hello all,
>
>Got something strange. I use a pcf 8583 timer (clock ic), that has a osci
>and osco pin. (Oscillator in, and oscillator out). According specification a
>32,768khz crystal must be pleased between these two pins, and a cap must be
>places between osci and Vdd.
They appear to require a fixed cap. (method 1) or a small trimmer cap
(method 2) between OscI and Vdd. - which method did you use, and what value
are you using ?
>My timer works fine, but much to slow. Tried a lot, nothing makes my timer
>runs faster.
>
>What is strange is the following. I can remove the cap, then it still works.
>I can remove the crystal, then it still works!! The timer keeps running but
>much to slow.
The cap. is apparently only an ancillary part, and is not required for
operation. Its presence is merely for ADJUSTING the time accurately. Much
depends on the tolerance and accuracy of your crystal oscillator. I'd check
that first. It may not be possible to firmly adjust a crystal with poor
tolerance features (IF that is the case). Many factors (ambient and other)
will effect the preformance of the crystal as well.
>The only way it runs faster is if i move my hand near the osci and osco pins
>of the chip, then a sort of interference seems to exist.
The natural capacitance of your body, and/or the heat from your hand can be
coming into play.
>can anybody help me out?
That's the best I can do, but I'm sure the Radio Amateurs, and more
technically minded folks may have other suggestions.
>thanks a lot in advance Pieter-Jan
Sure
Regards,
Bruce Bates
>_________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
>
>Share information about yourself, create your own public profile at
>http://profiles.msn.com.
Comments
Got something strange. I use a pcf 8583 timer (clock ic), that has a osci
and osco pin. (Oscillator in, and oscillator out). According specification a
32,768khz crystal must be pleased between these two pins, and a cap must be
places between osci and Vdd.
My timer works fine, but much to slow. Tried a lot, nothing makes my timer
runs faster.
What is strange is the following. I can remove the cap, then it still works.
I can remove the crystal, then it still works!! The timer keeps running but
much to slow.
The only way it runs faster is if i move my hand near the osci and osco pins
of the chip, then a sort of interference seems to exist.
can anybody help me out?
thanks a lot in advance Pieter-Jan
_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
Share information about yourself, create your own public profile at
http://profiles.msn.com.