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'[EE]: Crystal oscillators'
2000\07\27@084527 by Jinx

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I was trying to knock up an external clock for the PIC. I say "was"
because every single can I tried, 8-pin base and 14-pin base, gave
a less than useful output. I've a selection of 30 from 4MHz to 50MHz,
mostly carefully salvaged from old PCs and a couple of new 10MHz
ones as well. Connection seems to be simple enough 0V, +5 and
o/p. AKAIK none use the fourth pin functions, I think they may be a
bit old, but I tried anyway. None give anywhere near a full logic swing,
most < 1Vpp and the best only +0.8 to +2, which isn't enough to use a
buffer gate. Looked up circuits using them and pdfs from Toyocom and
Kyosera but can't for the life of me see what the problem is. As per test
circuits, can supply is regulated and decoupled and a 15pF test load,
which seems to make no difference. Any suggestions ? I can't believe
all 30 are hopelessly stuffed. Well, not yet. I haven't had a chance to get
them in-circuit and do evil things to them.

TIA

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2000\07\27@100406 by Thomas C. Sefranek

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Jinx wrote:

{Quote hidden}

I ONLY dirve my PIC with 4 pin oscillators and have had NO problems.
The signal output is a full 0 to 5 volts.

Could you be trying to drive an output pin?
Or a mis-configured Oscillator option?

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2000\07\27@101233 by Simon Nield

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Most 4 pin oscillators I have seen have 2 power pins, and the other pins are the input and output of
an inverter. The crystal is connected in parallel with the inverter. Could be you are consistantly
using the pin connected to the input of the inverter (i.e. the 'unbuffered' output). Try changing to
the other pin ?

Simon

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2000\07\27@101442 by Barry King

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Hey Jinx,

> Any suggestions ? I can't believe
> all 30 are hopelessly stuffed. Well, not yet.

Very unlikely, since they are not all pulls from the same source.

I THINK all those osc cans are push-pull outputs, but have you tried
a pull-up resistor, just for drill?

This may be stupid, but how are you measuring the output swing?
Could the measurement be off?  (Scope not cal'd, something?)

Spock: "Fascinating, captain."

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NRG Systems "Measuring the Wind's Energy"
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Check out the accumulated (PIC) wisdom of the ages at:
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2000\07\27@102522 by James Paul

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Jinx,

FYI, some canned oscillators use the 4th pin for a tristate signal.
So, you now have pin 14(8) as +5V, Pin 7(4) as Ground, Pin 8(5) as
Output and Pin 1(1) as O/P enable.  Chances are the ones you have
are not the tristatable type, but you never know.

                                           Regards,

                                             Jim



On Thu, 27 July 2000, "Thomas C. Sefranek" wrote:

{Quote hidden}

jimspamKILLspamjpes.com

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2000\07\27@104008 by Robert A. LaBudde

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At 12:46 AM 7/28/00 +1200, Jinxu wrote:
>I was trying to knock up an external clock for the PIC. I say "was"
>because every single can I tried, 8-pin base and 14-pin base, gave
>a less than useful output. I've a selection of 30 from 4MHz to 50MHz,
>mostly carefully salvaged from old PCs and a couple of new 10MHz
>ones as well. Connection seems to be simple enough 0V, +5 and
>o/p. AKAIK none use the fourth pin functions, I think they may be a
>bit old, but I tried anyway. None give anywhere near a full logic swing,
>most < 1Vpp and the best only +0.8 to +2, which isn't enough to use a
>buffer gate. Looked up circuits using them and pdfs from Toyocom and
>Kyosera but can't for the life of me see what the problem is. As per test
>circuits, can supply is regulated and decoupled and a 15pF test load,
>which seems to make no difference. Any suggestions ? I can't believe
>all 30 are hopelessly stuffed. Well, not yet. I haven't had a chance to get
>them in-circuit and do evil things to them.

I've noticed can oscillators deliver only ~ 4.2 V for a high. They are also
temperamental about how much current you draw. Voltage drops rapidly with
the load.

I suggest checking how much load you're imposing. Keep the current draw to
1 mA if possible.

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2000\07\28@115347 by Dan Michaels

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Jinx wrote:
>I was trying to knock up an external clock for the PIC. I say "was"
>because every single can I tried, 8-pin base and 14-pin base, gave
>a less than useful output. I've a selection of 30 from 4MHz to 50MHz,
>mostly carefully salvaged from old PCs and a couple of new 10MHz
>ones as well. Connection seems to be simple enough 0V, +5 and
>o/p. AKAIK none use the fourth pin functions, I think they may be a
>bit old, but I tried anyway. None give anywhere near a full logic swing,
>most < 1Vpp and the best only +0.8 to +2, which isn't enough to use a
>buffer gate. Looked up circuits using them and pdfs from Toyocom and
>Kyosera but can't for the life of me see what the problem is. As per test
>circuits, can supply is regulated and decoupled and a 15pF test load,
>which seems to make no difference. Any suggestions ? I can't believe
>all 30 are hopelessly stuffed. Well, not yet. I haven't had a chance to get
>them in-circuit and do evil things to them.
>


It sounds like your test lashup may be loading down the oscillators.
Too much stray capacitance/etc. I have an oscillator board I jigged
up using a cheapo Radio Shack pcb [bakelite or something equally
crappy], and when I plug in faster oscillator chips, the signals go
down into mud. However, in this case, usually only freq >20 Mhz or
so, are affected.

Also, if you are using a whiteboard for testing, they have quite a
bit of stray capacitance between adjacent channels.

best regards,
- danM

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'[EE]: Crystal oscillators'
2000\08\04@060430 by -1?Q?Jerko_Golubovi=E6?=
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----- Original Message -----
From: Jinx <joecolquittspamspam_OUTCLEAR.NET.NZ>
To: <@spam@PICLISTKILLspamspamMITVMA.MIT.EDU>
Sent: Thursday, July 27, 2000 2:46 PM
Subject: [EE]: Crystal oscillators


> I was trying to knock up an external clock for the PIC. I say "was"
> because every single can I tried, 8-pin base and 14-pin base, gave
> a less than useful output. I've a selection of 30 from 4MHz to 50MHz,
> mostly carefully salvaged from old PCs and a couple of new 10MHz
> ones as well. Connection seems to be simple enough 0V, +5 and
> o/p. AKAIK none use the fourth pin functions, I think they may be a
> bit old, but I tried anyway. None give anywhere near a full logic swing,

Pin that is left-out is unconnected on all examples.

> most < 1Vpp and the best only +0.8 to +2, which isn't enough to use a
> buffer gate. Looked up circuits using them and pdfs from Toyocom and
> Kyosera but can't for the life of me see what the problem is. As per test
> circuits, can supply is regulated and decoupled and a 15pF test load,
> which seems to make no difference. Any suggestions ? I can't believe
> all 30 are hopelessly stuffed. Well, not yet. I haven't had a chance to
get
> them in-circuit and do evil things to them.

Try de-coupling +5V with both MKT and Tantal if you did not. Power supply
should be "hard"
Try looking on scope if it is stable or not.
They should give +5Vpp as far as I know.

I have one floating somewhere so I will try it myself and will inform you on
results.

Jerko Golubovic
9A6JGJ

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