duty cycle and sine waves

T

Tom Del Rosso

Guest
I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave. The professor provided a formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.


--
Reply in group, but if emailing add one more
zero, and remove the last word.
 
Tom Del Rosso wrote:
I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave. The professor provided a formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.


Average voltage in a square wave? I think that would be more appropriate
Click to expand...
to say average in a sine wave or pulse train.

Avg = 2/Pi; Vp = Peak Voltage; Pk = RMS*1.414;

in any case, Vavg = Vp in a 50% duty square wave (+&-) No difference
there.

A pulse train, that is an ON and base line off, no (-)

Vavg = (b/a)*Vp;
B = ON Time, A = the time from the start of ON time to the next
start of on time.


In a sine wave the average is 2/pi * Vp = 0.636 * Vp

A triangle wave:

Vavg = Vp * .5;

A trapezoid wave

Vavg = A+B / 2* A *Vp

(A) being the base line width and (B) being the Peak width and Vp
being the Peak voltage.


Jamie
 
On Sun, 23 Jan 2011 08:39:35 -0500, "Tom Del Rosso"
<td_03@att.net.invalid> wrote:

I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave.
Click to expand...
Sounds meaningless to me. What was the answer?

John
 
John Larkin wrote:
On Sun, 23 Jan 2011 08:39:35 -0500, "Tom Del Rosso"
td_03@att.net.invalid> wrote:


I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave.

Sounds meaningless to me. What was the answer?
Click to expand...
50%

--Winston
 
On 01/23/2011 05:39 AM, Tom Del Rosso wrote:
I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave. The professor provided a formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.


"Duty cycle of a sine wave" works as well as "Blood pressure of a pine
Click to expand...
tree".

For some specific purpose there may be an _equivalent_ between the duty
cycle of a square wave and of a sine wave. Or maybe the prof was
thinking 50% (which is oddly obvious). Or something.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
 
"Tim Wescott" wrote in message
news:4KydncJeRY5BGaHQnZ2dnUVZ_jWdnZ2d@web-ster.com...

On 01/23/2011 05:39 AM, Tom Del Rosso wrote:
I was talking to a guy currently in college who had a lab in which he had
to
calculate the duty cycle of a sine wave. The professor provided a formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.


"Duty cycle of a sine wave" works as well as "Blood pressure of a pine
Click to expand...
tree".

For some specific purpose there may be an _equivalent_ between the duty
cycle of a square wave and of a sine wave. Or maybe the prof was
thinking 50% (which is oddly obvious). Or something.

Tim Wescott
I usually find it non-productive to guess what the assignment was meant to
accomplish.
A good deal of the time the assignment was not even perceived correctly by
the student.
They come here looking for answers but they don't know the question.

Tom
 
Tim Wescott wrote:
On 01/23/2011 05:39 AM, Tom Del Rosso wrote:
I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave. The professor provided a formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.


"Duty cycle of a sine wave" works as well as "Blood pressure of a pine
tree".

For some specific purpose there may be an _equivalent_ between the duty
cycle of a square wave and of a sine wave. Or maybe the prof was
thinking 50% (which is oddly obvious). Or something.
Click to expand...

50%, if the DC offset is zero.


--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.
 
"Tom Del Rosso"
I was talking to a guy currently in college who had a lab in which he had
to calculate the duty cycle of a sine wave. The professor provided a
formula which he didn't remember. What's this about? In a square wave
it's proportional to the average voltage, so I thought maybe it's a matter
of having a DC component.
Click to expand...

** Normally, continuous sine and square waves are bipolar waves with average
values of zero - so, unless gated on and off, their duty cycles are both 1
or 100%.

With a rectangular pulse wave that only swings from zero to some value, the
duty cycle is proportional to the average value - only becoming 1 when the
average and peak values are identical.

If a (continuous) sine wave is offset from zero - it has an average value
the same as that offset.

The " duty cycle of a sine wave" is, as my high school maths teacher would
have wryly said - " undefined ".



..... Phil
 
John Larkin wrote:
Sounds meaningless to me. What was the answer?
Click to expand...
I didn't ask what the answer or the "right" answer were.


--
Reply in group, but if emailing add one more
zero, and remove the last word.
 
Tom Biasi wrote:
I usually find it non-productive to guess what the assignment was
meant to accomplish.
A good deal of the time the assignment was not even perceived
correctly by the student.
They come here looking for answers but they don't know the question.
Click to expand...
Possibly he got the term mixed up with phase or something. It's even
possible the professor did.


--
Reply in group, but if emailing add one more
zero, and remove the last word.
 
On Sun, 23 Jan 2011 16:59:36 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Tim Wescott wrote:

On 01/23/2011 05:39 AM, Tom Del Rosso wrote:
I was talking to a guy currently in college who had a lab in which he had to
calculate the duty cycle of a sine wave. The professor provided a formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.


"Duty cycle of a sine wave" works as well as "Blood pressure of a pine
tree".

For some specific purpose there may be an _equivalent_ between the duty
cycle of a square wave and of a sine wave. Or maybe the prof was
thinking 50% (which is oddly obvious). Or something.


50%, if the DC offset is zero.
Click to expand...
100%. 1-((time@zero)/time(non-zero))x100%
 
Tim Wescott wrote:
On 01/23/2011 05:39 AM, Tom Del Rosso wrote:
I was talking to a guy currently in college who had a lab in which he had
to
calculate the duty cycle of a sine wave. The professor provided a
formula
which he didn't remember. What's this about? In a square wave it's
proportional to the average voltage, so I thought maybe it's a matter of
having a DC component.

"Duty cycle of a sine wave" works as well as "Blood pressure of a pine
tree".

Well, with Maple it can matter. :)
Click to expand...

I am a Druid; I have been washed in the blood of The Tree. ;-)

(That's what you tell people when they comment on the roach clip pendant.)

Cheers!
Rich
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top