Searching \ for '[EE] Crystals and Oscillators' 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/timers.htm?key=oscillator
Search entire site for: 'Crystals and Oscillators'.

Exact match. Not showing close matches.
PICList Thread
'[EE] Crystals and Oscillators'
2009\02\18@195124 by solarwind

picon face
I've been trying to learn about the different kinds of oscillators and
I couldn't find any good information on it. (If anyone has any
info/links, please post).

So what's the difference between a plain crystal
(http://www.futurlec.com/ICCrystalsMain.shtml)  and a crystal
oscillator (http://www.futurlec.com/ICCrystalsOscillators.shtml)? I am
trying to build a 1 Hz pulse using a 32768 Hz crystal and a divider
IC, but I have very little knowledge on the subject.

A whole bunch of questions about crystals, RC oscillators and other
oscillators and don't know where to find the answers.

--
solarwind

2009\02\18@212025 by Jesse Lackey

flavicon
face
Hi - this isn't directly a resource for crystals and whatnot, but if you
don't have "Art of electronics" by Horowitz & Hill, you should get it
asap.  While it is dated in some ways, it is by far the best coverage of
"timeless fundamentals" and I expect to refer to it occasionally for
decades to come.  If you're serious about learning a breadth of topics
in electronics, this is the book for you.  Why would one use a crystal
vs. oscillator?  What circuits drive different types of crystals?  How
accurate are they, and what affects accuracy?  It is in there.  The
specific parts mentioned are old and often obsolete, and it doesn't
matter whatsoever, because it is the how/why discussion that makes it so
valuable and timeless.

I used it and some online references (including PICLIST) while debugging
intermittent problems with a 32Khz RTC design, and now I know a lot more
about it all.

The writing style and clarity are so good you can just open it and read
and get a great tour of the hows and whys of a vast range of electronics
topics.

When I have a serious head-scratcher problem, I read H&H, look online
and search PICList archives, and then ask questions here having "done my
homework", which everyone appreciates - it keeps the SNR high and
discussions interesting.

Have fun,
J


solarwind wrote:
{Quote hidden}

2009\02\18@220848 by fred jones

picon face

Excellent post Jesse, but yours always are.

FJ


{Quote hidden}

_________________________________________________________________
See how Windows Mobile brings your life together—at home, work, or on the go.
http://clk.atdmt.com/MRT/go/msnnkwxp1020093182mrt/direct/01/

2009\02\18@230524 by Larry Bradley

flavicon
face
I haven't looked up the references you give, but a crystal oscillator would
normally be a crystal plus the active components (transistors, or logic
gates) to make a complete oscillator.

A crystal by itself is just a frequency-determining component. It requires
some other components to make an oscillator.

For example, the PIC can run with an internal RC oscillator, but it also will
run just by connecting a crystal (for example, a 10 mHz crystal) and two
capacitors to the OSC1 and OSC2 pins.

To do what you want ( generate a 1 Hz pulse), take a look at the 4060 CMOS
oscillator/divider chip. Google the chip to find a data sheet. It describes
how to connect up a crystal.

And I second the purchase of The Art of Electronics - it is an excellent book.

Larry



Original Message:
>
I've been trying to learn about the different kinds of oscillators and
I couldn't find any good information on it. (If anyone has any
info/links, please post).

So what's the difference between a plain crystal
(http://www.futurlec.com/ICCrystalsMain.shtml) and a crystal
oscillator (http://www.futurlec.com/ICCrystalsOscillators.shtml)? I am
trying to build a 1 Hz pulse using a 32768 Hz crystal and a divider
IC, but I have very little knowledge on the subject.

A whole bunch of questions about crystals, RC oscillators and other
oscillators and don't know where to find the answers.

--
solarwind

2009\02\19@042623 by solarwind

picon face
I found the 4060 oscillator circuit diagram:
http://img3.imageshack.us/img3/5346/crystaloscillator4060ou2.png

I see two resistors and two capacitors. What is the purpose for them?
Why those specific values for the capacitors? I thought the crystal is
supposed to be the only thing there that determines frequency.

2009\02\19@072220 by olin piclist

face picon face
solarwind wrote:
> So what's the difference between a plain crystal
> (http://www.futurlec.com/ICCrystalsMain.shtml)  and a crystal
> oscillator (http://www.futurlec.com/ICCrystalsOscillators.shtml)?

A crystal is the bare passive component that can be used to make a accurate
oscillator.  A crystal oscillator is the crystal with the circuitry around
it to make the whole oscillator.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2009\02\19@080743 by Forrest W. Christian

flavicon
face
I will agree that AoE by H&H is an invaluable reference.

I have also found that a more recent book "Practical Electronics for
Inventors" by Paul Schertz is an excellent complement as well.   I find
that it's writing style is a lot easier to comprehend than some portions
of the Art of Electronics, and if I could only have one of the two
volumes, I'd probably end up with the Practical Electronics book.

Generally, I'll go to the Practical Electronics book first for the
general overview, and often enough to make a circuit work.  If I need
more details, I'll then consult the Art of Electronics.

Jesse Lackey wrote:
{Quote hidden}

2009\02\19@093859 by Bob Axtell

face picon face
Usually, the best idea is to consult application notes for the chips
you are planning to use.
While there ARE different types of oscillators, this knowledge is
rarely needed anymore.

It will save you some time, I think.

--Bob

On Wed, Feb 18, 2009 at 5:51 PM, solarwind <spam_OUTx.solarwind.xTakeThisOuTspamgmail.com> wrote:
{Quote hidden}

> -

2009\02\19@094417 by PAUL James

picon face

Solarwind,

Go to the library, or your local ham radio store, and get a copy of THE
RADIO AMATEUR's HANDBOOK.
That has the info you're looking for, plus about 2 tons more.  You'll
use it often.
The last time I bought a copy, they were about $30.00 or $35.00 USD.

Jim   KA9QHR

{Original Message removed}

2009\02\19@125432 by Larry Bradley

flavicon
face
The 15 meg resistor biases the logic gate into the active region (as opposed
to being ON or OFF, it is part way between - this makes it behave more like
an analog circuit).

The 330k resistor is in series with the crystal, and serves to limit the
current trhough the crystal.

The two capacitors are to cause a phase shift so that the circuit will
oscillate. The 39 pf is variable to allow you to tune the curcuit to exactly
32768 Hz.

A crystal behaves like a tuned circuit - it looks like a large inductor in
series with a small capacitor, with another small capacitor across this
series circuit.

The value of the series resistor depends on the crystal - if you don't have
it there, the crystal may have too much current and fracture. Higher frequeny
crystals (e.g. 10 mHz) will normaly use  smaller value - I'm using 3.9K with
a 4060.

The capacitor also depend on the crystal - crystals are designed to oscillate
at their marked frequency with a specific value of external capacitance. For
example, a lot of the xtals sold for microprocessor use want to have 36 pf as
the external capacitance. For PICs. you will frequently see 22 or 33 pf caps
in the xtal circuit.


Google "crystal oscillators" and then duck - there is lots of stuff to read
out there.

Larry



Original Message:
>
I found the 4060 oscillator circuit diagram:
http://img3.imageshack.us/img3/5346/crystaloscillator4060ou2.png

I see two resistors and two capacitors. What is the purpose for them?
Why those specific values for the capacitors? I thought the crystal is
supposed to be the only thing there that determines frequency.

2009\02\19@132031 by Derward Myrick

picon face

----- Original Message -----
From: "PAUL James" <.....James.PaulKILLspamspam@spam@colibrys.com>
To: "Microcontroller discussion list - Public." <piclistspamKILLspammit.edu>
Sent: Thursday, February 19, 2009 8:43 AM
Subject: RE: [EE] Crystals and Oscillators


>
> Solarwind,
>
> Go to the library, or your local ham radio store, and get a copy of THE
> RADIO AMATEUR's HANDBOOK.
> That has the info you're looking for, plus about 2 tons more.  You'll
> use it often.

Solarwind

Go to this site they have the 1996 hand book in PDF.

This link puts you in the oscillator chapter.

http://mxh.strefa.pl/pliki/tech/book2006/10.pdf


Derward Myrick  KD5WWI

2009\02\19@132806 by Thomas C. Sefranek

face picon face
-----Original Message-----
From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu] On Behalf Of
solarwind
Sent: Thursday, February 19, 2009 4:26 AM
To: Microcontroller discussion list - Public.
Subject: Re: [EE] Crystals and Oscillators

I found the 4060 oscillator circuit diagram:
http://img3.imageshack.us/img3/5346/crystaloscillator4060ou2.png

I see two resistors and two capacitors. What is the purpose for them?
Why those specific values for the capacitors? I thought the crystal is
supposed to be the only thing there that determines frequency.
--



330K limits the drive current to the crystal, you CAN crack the crystal with
too much drive!
15M is feedback.
The crystal usually requires the capacitors for stability.
(It is possible to get the crystal to source odd harmonics of the printed
frequency.)

 *
 |  __O    Thomas C. Sefranek  WA1RHPspamspam_OUTARRL.NET
 |_-\<,_   Amateur Radio Operator: WA1RHP
 (*)/ (*)  Bicycle mobile on 145.41MHz PL74.4

ARRL Instructor, Technical Specialist, VE Contact.
hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

2009\02\19@145134 by John Coppens

flavicon
face
On Thu, 19 Feb 2009 04:25:39 -0500
solarwind <@spam@x.solarwind.xKILLspamspamgmail.com> wrote:

> I see two resistors and two capacitors. What is the purpose for them?
> Why those specific values for the capacitors? I thought the crystal is
> supposed to be the only thing there that determines frequency.

The 15M feeds DC back from the output of the gate, and puts it in a
linear state (so it amplifies linearly - more or less).

The 330k reduces de current from the output to the capacitor - the
largest power consumption in the circuit is charging and discharging it.

The two capacitors have several functions, but one of the specs of the
crystal is that it needs a certain C in parallel to be exactly at 32768
Hz. (That's why one of the caps is variable - the total cap in parallel
to the crystal is 10pF in series with 1/2 of the 39 pF, and the input C
of the gate - about 5pF extra). Also, the caps improve the phase
difference needed to oscillate, and avoid stray 'parasitic' capacitance
oscillation. Sometimes the internal C of a crystal is sufficient to
oscillate at another (higher) frequency.

John

2009\02\19@154830 by solarwind

picon face
On Thu, Feb 19, 2009 at 8:07 AM, Forrest W. Christian
<KILLspamforrestcKILLspamspamimach.com> wrote:
{Quote hidden}

I'll acquire these books. Thank you!

--------------------

On Thu, Feb 19, 2009 at 9:43 AM, PAUL James <RemoveMEJames.PaulTakeThisOuTspamcolibrys.com> wrote:
> Solarwind,
>
> Go to the library, or your local ham radio store, and get a copy of THE
> RADIO AMATEUR's HANDBOOK.
> That has the info you're looking for, plus about 2 tons more.  You'll
> use it often.
> The last time I bought a copy, they were about $30.00 or $35.00 USD.
>
> Jim   KA9QHR

Will get. Thanks!

--------------------

On Thu, Feb 19, 2009 at 12:54 PM, Larry Bradley <spamBeGonelarry.bradleyspamBeGonespamncf.ca> wrote:
> The 15 meg resistor biases the logic gate into the active region (as opposed
> to being ON or OFF, it is part way between - this makes it behave more like
> an analog circuit).

This is one term that has really been irritating me. No matter where I
look, I can't find the definition of "bias" in electronics terms. I
have no idea what it means, but I'm sure one of the above mentioned
book will have it so I will look there.

> The 330k resistor is in series with the crystal, and serves to limit the
> current trhough the crystal.
>
> The two capacitors are to cause a phase shift so that the circuit will
> oscillate. The 39 pf is variable to allow you to tune the curcuit to exactly
> 32768 Hz.

I thought the purpose of a crystal was to resonate at *exactly* that
frequency. Why does it need another component to tune it? So if you
attach a variable capacitor to it like some circuits suggest, wont you
end up with a slightly different frequency if you adjust it by hand?
(Since it's very hard to tune by hand?)

--------------------

On Thu, Feb 19, 2009 at 1:19 PM, Derward Myrick <TakeThisOuTwdmyrickEraseMEspamspam_OUTearthlink.net> wrote:
> Solarwind
>
> Go to this site they have the 1996 hand book in PDF.
>
> This link puts you in the oscillator chapter.
>
> http://mxh.strefa.pl/pliki/tech/book2006/10.pdf

Beautiful! Thanks!



And thanks to everyone else who answered.

--
solarwind

2009\02\19@170330 by Larry Bradley

flavicon
face
"Bias" in electronics refers to a voltage (or current) applied to an active
component (such as a transistor) to set up it's DC operating conditions .

For example, if you connect an NPN transistor with its emitter to ground, its
collector to +5 volts via a 1 kilohm resistor, and just connect the base to
ground, nothing happens - the transistor will not conduct, as there is no
base current. If, however, you connect the base to the +5 volts via the
PROPER VALUE of resistor, then some base current will flow, and thus some
collector current will flow. Now the transistor can act as an amplifer.

This isn't the best way to bias a transistor, but it illustrates the point.

The 4060 oscillator is just a logic gate I(basically a digital inverter).
Such a device has only two normal states -off and on - the output will either
be at ground or at Vcc (e.g. +5v). Since it is an inverter, if there is +5
volts at the input, there will be 0 v at the output. And vice-versa.

If you connect a proper value of resistor from the output back to the input,
the output can be set to be half-way between 0 and 5v. Now the inverter can
behave like an amplifier - a little change of voltage on the input gives a
larger change on the output. Or, by using  feedback, it can be made into an
oscillator.

Using a resistor and a capacitor in the feedback loop, you can create an
oscillator, but it won't be terribly accurate. This is what the PIC does for
its internal RC oscillator.

Now, as to the crystal. Recall that I said in my previous post that a crystal
is equivlant to an inductor in series with a capacitor, with another
capacitor (the stray capacitance of the holder) across the series circuit.

The xtal by itself, when put in the proper type of oscillator circuit will
oscillate at a certain frequency, as determined by the xtal's parameters and
any stray capacitance in the circuit (remember, it is behaving like tuned
circuit - and inductor and capacitor).  Any additional capacitance in the
circuit will result in a change in the frequency - just as if you had an
oscillator made from an actual inductor and capacitor.

Xtal manufacturers know that there is always going to be some stray
capacitance in a circuit ( a few pf), thus they make the xtal so that it's
native frequency is a bit high, and they specify a capacitance (such as 18pf)
that when applied externally will cause the xtal to oscillate at the
specified frequency.

Re books:

The "Art ..." and other books can be expensive, but very useful. Check your
public library for it and other books on electronics. The ARRL Handbook is
frequently found in libraries. A new one is published every year, so you may
even find one in a local used book store. Or check for an Amateur Radio club
in your area - hams frequently have older copies, and may be happy to give
one to an eager student.

Larry



On Thu, Feb 19, 2009 at 12:54 PM, Larry Bradley <RemoveMElarry.bradleyspamTakeThisOuTncf.ca> wrote:
> The 15 meg resistor biases the logic gate into the active region (as opposed
> to being ON or OFF, it is part way between - this makes it behave more like
> an analog circuit).

This is one term that has really been irritating me. No matter where I
look, I can't find the definition of "bias" in electronics terms. I
have no idea what it means, but I'm sure one of the above mentioned
book will have it so I will look there.

> The 330k resistor is in series with the crystal, and serves to limit the
> current trhough the crystal.
>
> The two capacitors are to cause a phase shift so that the circuit will
> oscillate. The 39 pf is variable to allow you to tune the curcuit to exactly
> 32768 Hz.

I thought the purpose of a crystal was to resonate at *exactly* that
frequency. Why does it need another component to tune it? So if you
attach a variable capacitor to it like some circuits suggest, wont you
end up with a slightly different frequency if you adjust it by hand?
(Since it's very hard to tune by hand?)

2009\02\19@211402 by solarwind

picon face
On Thu, Feb 19, 2009 at 5:03 PM, Larry Bradley <larry.bradleyEraseMEspam.....ncf.ca> wrote:
{Quote hidden}

Thanks for the explanation, that helps a lot. I have already acquired
the Art of Electronics and Practical Electronics for Inventors.

2009\02\20@114540 by Gerhard Fiedler

picon face
solarwind wrote:

> On Thu, Feb 19, 2009 at 12:54 PM, Larry Bradley <EraseMElarry.bradleyspamncf.ca>
> wrote:
>> The 15 meg resistor biases the logic gate into the active region (as
>> opposed to being ON or OFF, it is part way between - this makes it
>> behave more like an analog circuit).
>
> This is one term that has really been irritating me. No matter where
> I look, I can't find the definition of "bias" in electronics terms. I
> have no idea what it means, but I'm sure one of the above mentioned
> book will have it so I will look there.

As so often, Wikipedia is useful :)

<http://en.wikipedia.org/wiki/Biasing_(disambiguation)> leads you to
<http://en.wikipedia.org/wiki/Biasing_(electronics)>. The first phrase
says:

"Biasing in electronics is the method of establishing predetermined
voltages and/or currents at various points of a circuit to set an
appropriate operating point."

That's basically it. What Larry wrote about is that a logic gate usually
has two main operation points (lo and hi). The area below lo and above
hi is generally a no-no (you're likely to destroy the device). However,
between lo and hi the device can be used, even though it's generally out
of spec. In that area, the digital part works as an analog part.

In short: When used as an oscillator, you have a (small) signal that
oscillates. To this small signal is added a "bias voltage", to keep the
sum in area between hi and lo.

Gerhard

2009\02\20@151700 by Sean Breheny

face picon face
When trying to bias a logic gate in the mid-region for analog
operation, you generally have to use an "unbuffered" gate. Most logic
gates are actually several stages in series to help improve the
device's gain (a single stage would generally only have a gain of
around 50 which would make the transition between low and high output
states be more like a ramp than a sharp jump). Buffered gates are
often not stable when biased mid-way.

Some logic families may be unbuffered by default. Others, like the
74HC series, are normally buffered and you have to get the UB version
(like 74HC04UB) for a true single-stage inverter.

Sean


On Fri, Feb 20, 2009 at 11:44 AM, Gerhard Fiedler
<RemoveMElistsEraseMEspamEraseMEconnectionbrazil.com> wrote:
{Quote hidden}

> -

More... (looser matching)
- Last day of these posts
- In 2009 , 2010 only
- Today
- New search...