Sine to Square
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Whats the easiest waht to convert a low frequency sine (10-100hz) to a square
wave? Opamps or a comparator?
[noparse][[/noparse]Non-text portions of this message have been removed]
wave? Opamps or a comparator?
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
way to do this conversion is to use a comparator (or an op amp) as a
zero crossing detector.
The idea is this. No matter what the characteristics of the sine wave
(frequency, amplitude), it will cross the zero point F times per second
(where F is the frequency in Hz). So if you take a comparator (or an op
amp with no feedback) and feed the signal into one input and ground the
other input, you will get a square wave out.
Real world problems:
1) The opamp either needs a negative supply, or you need to shift the
sine wave so it's zero point is in the middle of the supply range (and
then that becomes your ground).
2) The Ft of the op amp/comparator will determine the maximum frequency
you can handle.
3) You'll usually want to use a comparator since their outputs are
usually open collector transistor outputs and they are faster (work at
higher frequency and produce sharper square edges). That means you'd use
a pull up resistor to 5V on the output and the comparator will only
output a ground or float open.
See http://www.wd5gnr.com/opampneg.htm for some ideas.
Some links pulled off google:
http://www.ringolake.com/pic_proj/zcd/zcdmodem.html - Uses MAX232 to
provide +/- supply
http://wug.physics.uiuc.edu/courses/Phys344/344exp/Lab1Analog_Digital/la
b1.htm#Part_4_OpAmp_to_TTL_Interface_Zero_Cross
http://www.play-hookey.com/analog/comparators.html -- good but not the
way I'd do it.
Do a search for zero crossing detector op amp (or opamp) for more. Just
zero crossing detector will get you a lot of things you don't want.
Hope that helps.
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: Tim Stockman [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZWB5eSOU7Kscu1Ebw7z99j5tKYQ9PXtMTK8wBW1-RBS4mbEXAFbyfAbm3dFE5y-YH7qGc1_-P3nRHEV2UMMLy0iPC7JzGTTaZ6Txw9VutA]tim.stockman@s...[/url
> Sent: Tuesday, July 22, 2003 7:59 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Sine to Square
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> Whats the easiest waht to convert a low frequency sine
> (10-100hz) to a square wave? Opamps or a comparator?
>
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I would use a comparator......you don't need any extra parts as you need
with an op amp. The LM339 is a good choice. On the other hand, if you have
an opamp and some resistors in your junk box, and YOU DON'T HAVE the
comparator, go with the op amp. Kindest regards, Chuck Irwin
Original Message
From: "Tim Stockman" <tim.stockman@s...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, July 22, 2003 8:59 AM
Subject: [noparse][[/noparse]basicstamps] Sine to Square
> Whats the easiest waht to convert a low frequency sine (10-100hz) to a
square wave? Opamps or a comparator?
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
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>
> To UNSUBSCRIBE, just send mail to:
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Body of the message will be ignored.
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as a switch might be good enough, with a switching threshold of 0.6
volt. Or a logic gate--Schmitt trigger for fast rise times.
>Whats the easiest waht to convert a low frequency sine (10-100hz) to
>a square wave? Opamps or a comparator?