Sine wave to square pulses?

[blapcb]

I have a 12v sine wave (i.e. -12v to +12v) which I need to change to a square wave so I can get the frequency. What circuit can be used? I know it is something with possibly comparators but have been Googling a lot and did not find. Also can it be done without? How about just clipping it with zener and then how to shape it? Thanks.

 

[IanP]

Agh !, man ..
**broken link removed**
**broken link removed**

etc. etc. ...

 

[rakesh_trustworthy]

That can be acheived by a schmitt trigger, which converts any wave into square wave.......... you can implement it either by 1) using two transistors and resistors
and 2) using an OP-AMP with resistors. plz go through them.........
**broken link removed**
http://www.daycounter.com/Circuits/Schmitt-Trigger/Transistor-Schmitt-Trigger.phtml
http://en.wikipedia.org/wiki/Schmitt_trigger

 

[blapcb]

Agh !, man ..
**broken link removed**
**broken link removed**

etc. etc. ...

Thanks IanP! May I ask, what is IC1 in your circuit?

 

[IanP]

It can be any opamp eg. LM358 or comparator eg. LM311 ..

IanP

 

[blapcb]

It can be any opamp eg. LM358 or comparator eg. LM311 ..

IanP

OK I have re-created your schematic in LTSpice and have attached the result. I have a few questions:
1. How do I get rid of the pulse resulting from the down cycle of the sine?
2. Why does the square wave not start from zero but seems to be between 1.8v and 3.8v approx?

Thanks

 

[IanP]

Wow, that was very nice zero-crossing detector in action ..

I've changed this circuit a little bit (see opamp's inputs), so try it again ..

IanP
:|

 

[FvM]

For a better understanding of the LTSpice1.png results, read below comment from the LTSPICE manual:

A common error is to draft a resistor with value of 1M, thinking of a one MegaOhm resistor, however, 1M is
interpreted as a one milliOhm resistor. This is necessary for compatibility with standard SPICE practice.

The correct resistance value in SPICE notation is 1Meg.