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Topic: Square wave from crystal oscillator (Read 869 times) previous topic - next topic

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??


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

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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.

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.


12MHz isn't the ideal crystal.  32.768Mhz is better
See the attached for all you need


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". 


Jun 17, 2013, 11:52 pm Last Edit: Jun 17, 2013, 11:53 pm by dc42 Reason: 1
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.
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.


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...
--> 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

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