Question about triggering analogue outputs for a specified time interval after acquiring an analogue input

[REK]

Hi, I am using a NI-6259 BNC DAQ connected to a port with a beam break sensor for the input and a pump for the output.  Using the DAQ Assistant function I have it set up so that the pump will continuously be on so long as the laser beam is broken.  I would like to have it such that breaking the beam activates the pump for only a set interval of time.  I was wondering if there were some suggestions on how to go about doing this.

[Stefo]

Hi Rek,

I'm not sure if I understand properly. I think the best would be to post some more details about signals you measure, maybe timing diagram what you try to accomplish would be helpful.

If I read just question from header, then it is possible to generate signal for just specified period of time. If you have to do it one, then it should be fine to change continuous generation to finite samples. If you need to repeat the process, then you need to retrigger - which is not directly supported on M series boards (yours). However, you can use 2 counter which your board has, and you can create retriggerable, finite pulse train generation. This generated signal, you can use as sample clock source for your analog output. There is some example with explanation here: Creating a Delayed, Retriggerable and Finite Pulse Generator.

regards,

stefo

[REK]

The process only has to be performed once at the moment, so this task should be relatively simple.  The input sends out 5 V until the laser is broken, afterwhich it drops to 0 V.  Likewise the pump activates when the 5 V output drops to 0.  I'd simply like to break the laser and have the pump go for a controlled period of time and stop, even if the laser beam remains broken.

[Stefo]

Hi REK,

if you need to do it once, then change your continuous generation to finite samples and change start trigger to be digital edge, and active edge should be falling. You can use DAQ Assistant in simplyiest case to accomplish it.

Regards,

Martin