how to drive pulse train out at lower frequency

[Sidd Goyal]

Hi

I am using PCI-1426 to capture no. of frames using pulse train. Assume that I am capturing 25 frames per sec whenever pulse is high, which means that pulse train has a frequency of 25 Hz. I am also sending this pulse train out at external trig. But I want the same pulse train to be sent out at different frequency say at 5 Hz, which means I should get a pulse high after every 5 pulses of 25 Hz pulse train. Please tell me how can I do that?

Thanks

Sidd 

[Hueter]

Sidd

Do you want the slower pulse train to be a multiple of the other?

You said  "I want the same pulse train to be sent out at different frequency", could you clarify this, is the original pulse train going to be irregular? Do you want to aquire several seconds on the original then send out a slower train on this line, or will it just be a slower dervied clock?

[Sidd Goyal]

Hi

Let me explain you in detail. In a pulse train of 25 Hz, there are 25 highs in 1 sec. Suppose 1st high starts at t=0 sec, 2nd at .04sec and so on... I want the same pulse train out, but it should have less frequency than the  original one. If I assume that I should get a 5Hz pulse train out, It means that I should first pulse high at t=0 sec, 2nd pulse high at 0.2 sec.. so on. This 5 Hz pulse train should be synchronized with 25 Hz pulse train. The difference is that 5 Hz pulse train should get the 1st pulse high, then it should remove next 4 pulses from the 25 Hz pulse train, then it should go high again...and this goes over and over. I hope that I have clarified it very well.

Please ask me again of you have any doubts.

Thanks,

Sidd 

[Alain_S]

We still don't know if you need both frequencies at the same time or not?

If yes, the you have a problem 😞

If no, then just generate a frequency according to a user input 🙂

The way you explained it, the duty cycle of the 5Hz train won't be 50%, is that a problem?

[Sidd Goyal]

I need 25 Hz pulse train to capture 25 frames per sec, which can be done using pulse train easily and I dont need to send this pulse out at any external trigger. I want to connect another device to PCI which operates on 5 Hz frequency,which I need to send out at any of the external trigger.

Regards,

Sidd 

[Alain_S]

You mean, the 25Hz signal is software between the PC and the camera. No physical trigger line, read trigger wires, between PC & camera.

The 5Hz signal is hardware between PC and something unknown to us . Here there is a physical wire.

But you need to synchronise both of them.

Is that it?

mmmm....

Can't you just set & reset any digital I/O line based on that 25Hz signal?

Message Edited by Alain S on 07-08-2009 11:41 AM

[BCho]

Hey Sidd,

If you are able to generate your pulse train at 25 Hz, you should be able to use a second counter to generate your 5 Hz signal. All you have to do to ensure the these two pulses are synchronized is make sure you reference the same clock source when setting up your DAQmx task. This way the two pulses will be synchronized.

[Sidd Goyal]

Hey Ben,

Thanks for the information.

Suppose If I have generated two pulse trains of different frequencies as shown in IMAQ pulse train generation example. Can you please tell me how to synchronize those two different pulse trains.

Regards,

Sidd 

[Alain_S]

Hi Sidd,

I still don't understand your hardware 😞

First you wrote : "...and I dont need to send this pulse out at any external trigger."
From that I conclude that you trigger your camera by software. That there's no wire between the PC and your camera for the 25Hz trigger.

Now you write: "Suppose If I have generated two pulse trains of different frequencies as shown in IMAQ pulse train generation example."
So, what will it be?
Two hardware trigger lines or only one?

Regarding your question to Ben. The answer is in his post.
Maybe you overlooked the part : "...to ensure the these two pulses are synchronized is make sure you reference the same clock source..."

Can you make a drawing of your hardware, PC, camera, ..... and how they are connected.

That will clear out a lot of things

Regards

[Sidd Goyal]

Hi

I said I dont want to send out 25HZ pulse train because i am using it in labview to trigger the camera. As there are two ports (26 pin and 15 pin) on PCI-1426. It uses CC lines in 26 pin port to trigger camera. However I want to send the 5 Hz pulse train out at external trig (which is on 15 pin)  so that I can trigger another device.  

Sidd