How to trigger a TTL output with an analog input

[JohnPags]

Hello,

I have an apparatus for measuring the flame speed of various hydrocarbon/air mixtures.  The chamber uses central ignition as the means for igniting the mixture.  My goal is to film the ignition process with a high speed Phantom video camera.  I control the ignition with an analog output signal from a SCC-68 DAQ.  I would like to trigger the camera with the same signal that triggers the ignition sequence.  The camera is triggered with one TTL pulse so ideally I would connect the output analog voltage signal to an input analog voltage port that would be used to trigger a counter output that generates one pulse.

I have a sample VI that triggers a digital pulse each time the analog trigger level is met and it works for what I am trying to do but I do not understand how the two channels are connected. I also can't figure out how to make the VI end after just one pulse.  In the VI the digital counter is supposedly triggered using the /Dev1/ai/StartTrigger slot on the DAQ but nothing is connected to this slot.

I need to first figure out how to make the output_pulses_on_sine_wave.vi terminate after a single pulse is generated. Then I can try to incorporate it into the VI that I use to control the ignition and measure the temperature and pressure once the mixture is ignited.

John

[johnsold]

Why not generate a single Digital Output pulse and use it to trigger both the camera and the analog output signal for the ignition? 

The SCC-68 is a terminal block. It is not a DAQ device, only the connector to it.  Please tell us what actual DAQ device you have.

Lynn

[JohnPags]

I am using the USB-6259, sorry for the confusion.  I would be nice if I could trigger with an analog signal to the ignition system but it is controlled with a high voltage relay that operates when 12 volts are supplied to it. It really isn't a trigger as much as powering on the high voltage relay. To control it, I have a 12 V supply line that is switched closed using a SCC-RLY module.  Could I somehow connect the 12 V supply to one of the buses and use a digital trigger to supply the 12V on command to the high voltage relay?

Thanks for the quick response. 

[John_P1]

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@johnsold wrote:

Why not generate a single Digital Output pulse and use it to trigger both the camera and the analog output signal for the ignition? 

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/agree

You could even simply export the start trigger from the analog output task.

Best Regards,