Pages: [1]   Go Down
Author Topic: Square wave from crystal oscillator  (Read 686 times)
0 Members and 1 Guest are viewing this topic.
India
Offline Offline
Full Member
***
Karma: 0
Posts: 174
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Hey,
I have Googled and was not able to find a proper circuit for generating square wave from crystal oscillator. I am planning to use a Schmitt trigger to convert the sine to square. But how do I get sine from the crystal. Do i just need to apply a 5V dc across the terminals??
Thanks
Logged

Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 46
Posts: 2865
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Try... Googling Crystal Oscillator and read until you understand what you are reading.

Doc
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Manchester (England England)
Offline Offline
Brattain Member
*****
Karma: 602
Posts: 33358
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
But how do I get sine from the crystal
By putting it AS PART of a crystal oscillator circuit. There are lots and lots to chose from, but without knowing what frequency the oscillator is it is hard to give any advice.
Logged

India
Offline Offline
Full Member
***
Karma: 0
Posts: 174
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

What I need is a perfect 1hz square wave and don't want to use timers or op-amps. I am planning to use a 12Mhz crystal and do freq division.
Logged

SW Scotland
Offline Offline
Edison Member
*
Karma: 17
Posts: 1376
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

12MHz isn't the ideal crystal.  32.768Mhz is better
See the attached for all you need
http://forum.allaboutcircuits.com/newsgroups/viewtopic.php?t=422
Logged

Offline Offline
Edison Member
*
Karma: 32
Posts: 1282
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

A crystal by itself does not oscillate.   It's a resonant device something like a bell or a guitar string, and something needs to activate or "excite" it, to get it started and keep it going.

You can buy a crystal oscillator like this for 3 or 4 times the price of a crystal alone.   (That example is the wrong frequency).   You'll probably still need a frequency divider.   These have 3 connections:  +5V, ground, and output.   (There is usually a 4th unused pin.)

Most circuits you'll run-across will either use one of those oscillators, or in the case of a microprocessor/microcontroller (like the Arduino) the oscillator circuit is built-into the chip, and an external crystal is used.    You'll almost never see a crystal oscillator made "from scratch".   
Logged

United Kingdom
Offline Offline
Tesla Member
***
Karma: 223
Posts: 6593
Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I'd use an ATtiny25 with a 32768Hz crystal attached. I can't think of any other solution that uses only 3 components (including the decoupling capacitor). However, if you don't have the means to program an ATtiny then you will need a different solution, such as an MC14521B oscillator/frequency divider with a 4194304Hz crystal, 2 load capacitors and 2 resistors for the crystal, and a decoupling capacitor.
« Last Edit: June 17, 2013, 04:53:45 pm by dc42 » Logged

Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

Anaheim CA.
Offline Offline
Faraday Member
**
Karma: 46
Posts: 2865
...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Perhaps the simplest method would be to use a DS1307 and program it for a 1 second output pulse, The chip is quite capable of that and there are instructions in great plenty here in the Forum and the Playground too...
Logged

--> WA7EMS <--
“The solution of every problem is another problem.” -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Pages: [1]   Go Up
Jump to: