Square wave from crystal oscillator

Other Hardware General Electronics
1

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

2

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

Doc

3

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.

4

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.

5

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

6

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 [u]this[/u] 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".

7

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.

8

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...