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Square waves

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vortex2009

New Member




Hi all,

I do realise that the 555 Timer IC, gives out quite good Square waves..
but a square wave surely cant exsist: Reason I've got a thing about this is because, in my Study books.. square waves are made up of multiple sine waves... Of Which I find much more interesting.. "In the terms of the sound wave"

THIS might sound mad.. but say right you got a Timer (555) well thats been set and made to give out sq-waves.. but the makers of the Intergrated Chip.. what I mean all man made!! now Im not being funny here, Sine cosine are for real.. Alternating current.. like out of the mains socket.(60hz) over in England. dont get me Wrong Ive made endless circuits with that Chip.. firstly made by Signetics.. Question What year if anyone knows what Year did the very first 555 Timer chip, named "The Time machine!!!" come out..

Its not a argument Post here.. But say you build a astable circuit with the Timer.. ok R1 + R2 value + the C value... hook up a Speaker and you Just get out a Tone, buzz, thats all, Unless you FM it with a Second Timer.. and feed the second Timer from pin 3.. of which you all know,:) to pin 5 CV of the 1st Astable.. then it gets interesting...
other wise I personly think Sq waves are hopless.. Yes I know there used in Logic circuits.. computers.. on & on & on...

Hope know one gets anoyed with this Post because it's purely my opinion..

Cheers all
:eek:
 

kpatz

New Member
When you think of a square wave in terms of its frequency content (fundamental + harmonics), it can be "reconstructed" using multiple sine waves, or frequency/phase modulation of sine waves (google FM synthesis for more info on this--btw, synthesizers are one of my hobbies/obsessions). Using such techniques can yield something that has the same harmonic content as a square wave, but it won't necessarily look like a square wave on a scope.

But when you say, "a square wave surely can't exist", do you mean "can't exist in nature"? Like, you'll never see square waves rippling on a pond. That's probably true, unless there's something in the animal kingdom whose voice creates square waves.

Obviously they can "exist" in the world of electronics, as the 555 and logic ICs surely attest to... but, do they really? A true square wave would have an infinitely fast slew rate, transitioning from the "crest" to the "trough" instantaneously; in real life, there's always some slew, so a square wave generated by electronic circuits are more like a nearly-square trapezoid wave. ;)
 
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audioguru

Well-Known Member
Most Helpful Member
Alternating current.. like out of the mains socket.(60hz) over in England.
No.
The mains frequency in England is 50Hz.

What year if anyone knows what Year did the very first 555 Timer chip, named "The Time machine!!!" come out?
Look in Google. It was introduced to the market in 1971.

say you build a astable circuit with the Timer.. ok R1 + R2 value + the C value... hook up a Speaker and you Just get out a Tone, buzz, thats all.
Because a square wave sounds like a buzzer.
A triangle wave sounds like a violin.
A sine wave sounds something like a flute.
 

BrownOut

Banned
In fact, all square waves can be constructed as a summation of sine waves. If two waves have the same harmonic content, they they are identical, and will appare so on an oscilloscope. But if you truncate the harmoncis, for practicality, then you won't get the same wave. To summarize, square waves do exist, and they can be deconstructed in a summation of sin's. Wether you believe that or not, it is all true.
 
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Torben

Well-Known Member
I have to agree with kpatz--a true square wave cannot really exist in the physical world since infinite skew rate cannot exist. You cannot simple jump from one value to another with no intervening time lag. However, they can certainly exist mathematically and can also exist in that skew rates can be achieved which are higher than the ability of the measuring apparatus can measure.

So practically, yes: square waves can exist. Theoretically, no, in the real world, it's not *really* a square wave--but as far as you can tell, it is, so what's the difference? If it looks like a square wave and acts like a square wave (within the constraints of the current application), what difference does it make?

If it's square enough for the current application, it's OK to treat it as a square wave. IMHO.


Torben
 

BrownOut

Banned
If you're going to be that picky, you might as well say there is no such thing as a sine wave, because there will always be some finite distortion. The difference between an ideal square wave, and what is possible for generation is too small to even be concerned about. At least at low frequencies.
 

Hero999

Banned
Suqarewave also never have exactly 50% duty cycle, even after it's been put through a divide by two counter: the high side MOSFETs tend to switch slightly more slowly than the low side MOSFETs, in a CMOS IC.
 

Torben

Well-Known Member
If you're going to be that picky, you might as well say there is no such thing as a sine wave, because there will always be some finite distortion. The difference between an ideal square wave, and what is possible for generation is too small to even be concerned about. At least at low frequencies.
Read what I wrote again. That's exactly what I said.


Torben
 

crutschow

Well-Known Member
Most Helpful Member
Don't surf square waves. Stick to sine waves and the occasional rad tube. ;)
Large breaking waves look more like sawtooth waves.
 

crutschow

Well-Known Member
Most Helpful Member
As you might expect, it takes the summation of an infinite number of sine-waves to generate a perfect square-wave.
 
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