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Re: Welcome arb-92

Post by Admin on Sat Mar 10, 2018 6:04 pm

Ivan wrote:Hi Harry,
IMHO Arb wants to place his spreadsheet (probably in XLS format) somewhere for free download. PDF nor PNG is of no use in such case.
The simplest way may be to place it on Arb's web pages and post a link to this conference.

BR from Ivan
Hi Ivan,
I figured it depended on the size of the document. But I also suggested sending the documents to me to put on a server and give him the URL.
BR Harry

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Re: Welcome arb-92

Post by Ivan on Fri Mar 09, 2018 6:57 am

Hi Harry,
IMHO Arb wants to place his spreadsheet (probably in XLS format) somewhere for free download. PDF nor PNG is of no use in such case.
The simplest way may be to place it on Arb's web pages and post a link to this conference.

BR from Ivan

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Re: Welcome arb-92

Post by Admin on Thu Mar 08, 2018 6:49 pm

Hi Arb,
Great, I am glad I cold shed a little light, or nudge you in the right direction.

To post documents you can do a screen dump and post the picture, or you can upload the document to a free server and add a link.

If you have any difficulty then you can send me the document and I can place it on a server for you. Preferably a PDF that is not editable. I can then send you the URL.

Very best regards from Harry - SM0VPO

harry.lythall@sm0vpo.com
british.inteligence.sweden@sm0vpo.com
hotmail@sm0vpo.com

(All are valid addresses exactly as written, do NOT correct the spelling or word order ;-)

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Pierce Oscillator Worksheet

Post by arb-92 on Thu Mar 08, 2018 5:45 pm

Hej,
Thanks for your prompt answer
I would really hate being the one getting you into trouble with your better half…
Your reply did help in so much as it nudged me to finally do what I did not want to do in the first place: research the literature by myself…
It is not an easy subject, being a non-linear dynamic system, but certainly a fascinating one because of the contrast between the extreme accuracy which the Pierce quartz crystal oscillator is capable of and the wide tolerances encountered for most of its actual operating parameters.
This is a very fortunate coincidence for us but not a sufficient reason to abuse the circuit though.
I have a confession to make: I am a spreadsheet addict, a worksheet serving as my daily scratchpad for the past 37 years (since 1981: once I tested Visicalc, I never went back to do economic modeling on a mainframe computer as I did then, compiling programs written in Fortran or APL, etc…).
So, as usual then, I built a worksheet, for setting a Quartz-controlled Pierce-gate oscillator: nothing fancy! And since there is a logic to all madness, I also edited the notes taken during my readings, which were used in building the worksheet (took a bit longer than expecred to put together...).
Now, if I can be told how to join documents to a message, I'll gladly send both files...
Best,
ARB

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Re: Welcome arb-92

Post by Admin on Sun Feb 25, 2018 10:07 pm

Hello ARB,
I seem to have missed the question, but if you refer to the circuit of the Improved CMOS Synthesiser, you see that there are two resistors and two capacitors.

The 2K2 is simply a current limiting resistor to protect the crystal from excessive current that could damage it. 32kHz watch crystals, for example can be easily damaged since they are so fragile.

The 100K can be any value from about 47K to 270K. It biases the inverter gate into the linear region so it becomes an analogue amplifier (tip - CMOS can be used as DC, AF and RF amplifiers). The resistor can be connected to pins 10 and 11 as shown, but it is quite comon for this to be in parallel with the crystal (the other side of the current limiter).

The two capacitors are usually of the same value. If the crystal load capacitance (from specifications) is 20pf then C1 in series with C2 should be about 20pf (40pf + 40pf). But you must also subtract the residual capacitance. These values are not very critical for oscillation, but they affect the frequency, so one of them is often a preset trimmer capacitor for precise frequency adjustment.

There are many types of crystal oscillator configurations possible, some using a variable inductor for frequency trimming and presenting an exact capacitive load. There are also circuits to get the biggest frequency variation to allow some flexibility of crystal selection of circuit flexibility. But the circuit below is a standard circuit that works with almost any crystal.




Have I answered your question?

Very best regards from Harry - SM0VPO
(sorry but Maj-Lis is calling me - a bit late - should be in bed :-)

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Help needed: quartz crystal set-up

Post by arb-92 on Sat Feb 24, 2018 11:06 am

Hello,
Thank you for welcoming me at HHH.
A retired economist, having more time now to indulge on my hobby: analog audio and vacuum tubes, I happened to get to Harry’s website while searching for information on the CD4060 oscillator chip (employed by a couple of his circuits: CMOS synth and oscilloscope probe calibrator), and I have to say that, while not getting direct answers to my specific question so far, I found many other worthwhile tips and ideas on the site which I definitively intend to put to good use…
I wonder if anyone could tutor me or give directions to getting the design rules for calculating the handful of passive components which usually surround the quartz crystal fixing the oscillation frequency (clock) of a digital integrated circuit.
Let’s take the oscillator part of Harry’s CMOS synth project for (good) example:
How are the values of the capacitors (39pF and 100pF) and resistors (100k and 2k2) derived exactly?
My own needs span quartz crystal frequencies ranging anywhere from 4 to 10MHz, to be used with supplies ranging from 5VDC to 12VDC…
Any help appreciated!
Best,
ARB

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Welcome arb-92

Post by Admin on Wed Feb 21, 2018 7:53 pm

Welcome arb-92 to HHH and the forum.
Nice to have you onboard.
I have activcated your account and you can post, include links and pictures. Hope you have a nice time on the forum and please feel free to contibute or ask questions.
Very best regards from Harry - SM0VPO

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Re: Welcome arb-92

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