Mechie, It's running 0.02% too fast.
I'm getting an error of 18 seconds per 24 hours and thats using that 39pf trimmer on that data sheet.

Looks like I nead to use more pfs then the 39pf specified.
Is it ok to us more?

I also did not use a voltage regulator.Does it matter with crystals?
i used 4.5Volts (3* 1.5 volts AA batteries)

What does 100ppm mean?
Thanks

 

Have you zero beat the oscillator against a reference source?, or how have you set it up?.

I would expect the frequency to change as the batteries go flat, digital watches do!.

ppm is "parts per million".

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Nigel asks I bought some more caps to tune it (27 pf on both sides of the crystal).

I hooked up the seconds pulse of it to the parallel port.
Wrote a program in QBasic to tell me the time when the port receives a low/high input signal.
Qbasic's timer command has a resolution of 0.01 second.
I'm now getting an error or 0.01 second every 3000 seconds.
or an error of 0.28 seconds / 24 hours when compared to my pc clock. I think my pc clock is accurate to within a second per day when updated daily from the internet clocks

 

The crystal is tuned by altering the DIFFERENCE on the two sides of the crystal, so by adding to BOTH sides you're not really changing anything 8)

Sorry, but that's a REALLY poor way of trying to adjust it, the accuracy of the QBASIC program is going to be pretty poor, nowhere near as accurate as your untrimmed crystal!.

As your resolution is 0.01 seconds, by definition the accuracy can be no better than + or - 0.01 seconds, and the way the QBASIC timer command works will make it worse than that!.

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Nigel says Thanks for that info.


Nigel says I ran it continuously for a few hours and got an average of 0.01 seconds error per 3000 seconds, but i see what you are getting at.

Next time I will not run Qbasic.
will just let it run over night (12 hours) and see visually how many seconds its out.

I also have a seven segment thing showing seconds.

eg.
when it's 10:00:00 pm on my computers clock, I'll turn on the crystals power .
After 12 hours, I'll see if the seconds are still syncronizing with the pc clocks second hand.

Oh, I'll use a voltage reg too (i forgot to use it today).

Thanks

 

It is best to test your clock circuit after it has warmed-up. Its frequency will be stable and that's the way you will use it anyway. :lol:

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Uncle $crooge

 

You mean warmed up as in temperature or
run it under power for a period of time for it to stabalize?

 

Temperature.

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Uncle $crooge

 

Cool, I've been doing that and documenting the temperature of the room.

 

It's very interesting when you put 4 quartz clocks infront of you and you watch the second hands/display for a few hours

One of them, a no-named digital was a second slow only after 40 minutes.
Another, a seiko quartz analoge, was a second slow after a few hours.
compared to my pc clock.

Don't know the battery state of the clocks.
Interesting.

 

You should be aware that PC clocks are really poor time keepers (often out by minutes per day!), so you need to ensure it sets itself off the Internet before you take readings!.

If you have Teletext in your country?, try comparing it to the Teletext time (ensure you use the same channel every time though).

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Nigel says I never would have thought of that.
Pitty, I don't have a teletex tv.

I agree with what you said about updateing of the internet before taking time readings (which I have been doing).
My pc's clock is within 1 second/day compared to internet time servers.

 

You can't trust them!
When I had a VCR it set its clock automatically to "teletext?" from a TV station. Then it screwed-up. I e-mailed them and they thanked me for pointing out their problem and it took about 1 month for it to be fixed until it screwed-up again a few months later.
On my new digital recorder I just highlight the program on the cable TV's guide channel and push the Record button on my remote. It even knows if my program is delayed or runs into overtime. :lol:

__________________
Uncle $crooge

 

You can in the UK, where it was invented! :lol:

It doesn't sound like your TV stations are very reliable?.

Is that using a kind of PDC? (Program Delivery Control), which is a Teletext based system - which has flopped pretty well in the UK.

Or is it a digital TV system?, which again must send some kind of start and stop signals to accurately record a program - and obviously relies on these signal being inserted!.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

[quote="Nigel Goodwin"]It doesn't sound like your TV stations are very reliable?.[quote]
The station is an old non-profit American one. Canadian stations are newer and more reliable but don't broadcast the time signal.

Yeah, it's digital cable-TV. They must have a whole army of many people keying in the stuff. :lol:

__________________
Uncle $crooge