C / C++ / MFC

Period and Duty cycle calculation [modified]

14-Jul-09 0:01

Stuart Dootson wrote:
const std::string p = "ddddd";
std::string q;
q=p;

std::string q = "ddddd";

FFY

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sks8313-Jul-09 20:37

13-Jul-09 20:37

Hello,
I have a 2D waveform data (Sine/Square/Triangle). Could some one tell me how to calculate period and duty cycle from it.

Note:
I am new to this forum, if this is a wrong place to post this topic, some one re-direct me to correct place.

Thanks.

modified on Tuesday, July 14, 2009 2:47 AM

LittleYellowBird13-Jul-09 21:52

LittleYellowBird

13-Jul-09 21:52

Hi,

I'm not ure what you asking, a quick Google should tell you how to calculate period & duty cycle. Try to think of a more specific programming question and perhaps someone here can help you.

Ali

sks8313-Jul-09 22:17

13-Jul-09 22:17

I am just trying to implement the period and duty cycle calculation in a C++ class based on the waveform array data. Trying to figure out some formula to find those values.

Stuart Dootson13-Jul-09 22:32

Stuart Dootson

13-Jul-09 22:32

Period - find the max/min values of your waveform. Now look for the times when the waveform crosses (min+max)/2. The period should be double the time between adjacent crossings of that value.

Alternatively, calculate the FFT of the waveform and look for the big peak - that'll show dominant frequency in your signal.

Duty cycle[^] - Wikipedia defines as Duty cycle is the proportion of time during which a component, device, or system is operated. First you need to decide what the 'active' state of your waveform is and work out what fraction of time it's active.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

sks8313-Jul-09 23:01

13-Jul-09 23:01

Thanks Stuart.

But i have an unsymmetrical waveform data, so i couldnt use (max+min)/2 to determine the level crossing. Also without the sample rate of the waveform how can i find period by finding the total noOfSamples of a cycle.

Stuart Dootson13-Jul-09 23:05

Stuart Dootson

13-Jul-09 23:05

sks83 wrote:
without the sample rate of the waveform

If you don't know the sample rate, you can't calculate the period in terms of time - only in terms of samples.

sks83 wrote:
But i have an unsymmetrical waveform data, so i couldnt use (max+min)/2 to determine the level crossing

In that case, find the number of samples between maxima or minima.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Re: Period and Duty cycle calculation [modified]

Cedric Moonen13-Jul-09 23:07

Cedric Moonen

13-Jul-09 23:07

If your waves are "pure" (square, sine or pure triangular), you could calculate the time were the signal is positive and negative. You add those two times and you end up with the total period. The ratio of those times will give you the duty cycle.

To calculate those times, this is quite easy: simply walk over your points and check when the sign changes. At that time, you keep the time (start time) and walk over the data until the sign change (stop time). The difference between stop and start time gives you the time were the signal is negative or positive (depending of the sign).

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

sks8313-Jul-09 23:12

13-Jul-09 23:12

Thanks Cedric.

1. My waveform is not symmetric and it can have n number of cycles. Also waveform data may be clipped at the beginning.
2. If you could tell me how to determine the crossing level of the waveform. With that i can determine the period.

modified on Tuesday, July 14, 2009 5:18 AM

Cedric Moonen13-Jul-09 23:19

Cedric Moonen

13-Jul-09 23:19

sks83 wrote:
My waveform is not symmetric and it can have n number of cycles. Also waveform data may have clipped data at the beginning.

Not symetric is not a problem. What I mean is that if you have a very complex waveform (like sound), then this technique won't work. If a period of your signal is the time in which your signal is positive plus the time were the signal is negative, then this will work fine (and it is quite easy to implement).
If you have multiple cycles, that's fine, you can for instance do an average of all the positive times and all the negative times (well, that depends on your requirements of course).
For the clipping, simply skip the first half period: start your calculation were the sign of your signal is switching.

sks83 wrote:
2. If you could tell me how to determine the crossing level of the waveform. With that i can determine the period.

What do you mean by crossing level ? The time at which your signal sign changes ? If yes, then that is really easy to do: simply walk over your data points and check when the sign of your data changes.

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

sks8313-Jul-09 23:56

13-Jul-09 23:56

Hello cedric,
I could not walk through each data points, since i have more than 20,000 samples.
FYI
Unsymmetrical Sine waveform data is as below,
ON time
Start - 5V.
Stop - 5V.
Max - 7V.
OFF time
Start - 5V.
Stop - 5V.
Min - 1V.

There will not be any negative data points. So how could i find that the waveform crosses at 5V.

Re: command buttons in SDI

LittleYellowBird14-Jul-09 0:05

LittleYellowBird

14-Jul-09 0:05

Hi, You may well have 20,000 samples but you can still 'walk through' them, in fact you will have to analyse each point in some way to get the results you require.

I do not entirely follow the description of your waveform, but since you have no negative points you could find the time between two peaks (maximums) or troughs (minimums), this would be an equally valid measurement of period.

Hope that helps,

Ali

command buttons in SDI

Member 59031013-Jul-09 20:27

Member 590310

13-Jul-09 20:27

can we add command buttons to SDI application.

_AnsHUMAN_ 13-Jul-09 20:35

_AnsHUMAN_

13-Jul-09 20:35

Yes

You need to google first, if you have "It's urgent please" mentioned in your question.
Wink | ;-)

_AnShUmAn_

datetime control on Windows mobile 5.0 win32 application.

zakkas248313-Jul-09 20:23

zakkas2483

13-Jul-09 20:23

Respected all,
I am working with win32 application for windows mobile 5.0. I need use datetime control on one of the my dialog box. after adding the datetime control on the dialog box. The application compiled successfully but that dialog box is not loaded while running application.

Thank you.
Hiren.

Re: datetime control on Windows mobile 5.0 win32 application.

David Crow14-Jul-09 9:02

David Crow

14-Jul-09 9:02

If you remove the control from the dialog template, does the dialog then display?

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Socket

navneet198513-Jul-09 20:15

navneet1985

13-Jul-09 20:15

Any event fired by the windows on establishment of new socket?

Re: Socket

Michael Schubert14-Jul-09 0:52

Michael Schubert

14-Jul-09 0:52

Absolutely.

how to detect the data on the transmission line when using a comport

jitendrapothuru13-Jul-09 19:55

Re: how to detect the data on the transmission line when using a comport

13-Jul-09 19:55

Hi,
i am using comport communication in my application
so i have to detect whether the data is there on the tx line
or not and then send the data is there anyway to implement
this functionality

CPallini13-Jul-09 21:33

Re: how to detect the data on the transmission line when using a comport

13-Jul-09 21:33

Why do you need that? Don't you like output buffering?
Smile | :)

jitendrapothuru13-Jul-09 22:13

Re: how to detect the data on the transmission line when using a comport

13-Jul-09 22:13

no the output buffering was not working so
i want to implement this way... to transmit data

CPallini13-Jul-09 22:15

Re: how to detect the data on the transmission line when using a comport

13-Jul-09 22:15

Output buffering usually works. Could you please give more details about your problem?
Smile | :)

jitendrapothuru13-Jul-09 22:20

Re: how to detect the data on the transmission line when using a comport

13-Jul-09 22:20

actually i am implementing a functionality in
which the tx and rx will be in a session
so while i am sending the data at a baudrate(baudrate can be any)
this is coming out of session.even though its taking the whole value into the
tx buffer its abruptly comes out of session.

CPallini13-Jul-09 23:04

Re: how to detect the data on the transmission line when using a comport

13-Jul-09 23:04

Are you changing the baud rate on the fly, without closing and the opening again the port? I don't know if it might work, anyway you've to make sure to flush the buffer, before even trying.
Smile | :)

jitendrapothuru13-Jul-09 23:29