We need to trigger a voltage output from LabVIEW to initiate an external event.

[Massdog05]

We are attempting to measure a pressure event created by the discharge of gases from a .22-caliber powder charge (think .22 rifle, but no bullet, just pressure from powder burn).  We need to initiate the powder ignition from LabVIEW so we can simultaneously begin capturing data.

What is the VI component that allows for the output of an analog signal (trigger voltage) from the DAQ board while simultaneously initiating the capture of data?

Thanks. 🙂 

[LV_Pro]

What DAQ board are you using? You could also start capturing data, then trigger the event, which will assure that you have the beginning data.

[Dustin_D]

Hi ajmassey, 

I think the best thing to do assuming you will be able to start your physical events with a 5V digital pulse would be to configure a digital write task and an analog input task in parallel.  First you would start your AI task, then your digital task.  If you need reference on programming those tasks you can find examples in LabVIEW under Help»Find Examples then select Hardware Input & Output»DAQmx then the respective category. Here is an image to show you how the two of these would look together(for illustration I haven't properly configured the DAQmx Create Channel VIs) :

 

 This would start acquiring data and then trigger your your event.  From the sounds of what data you would be capturing you would probably be able to tell where it starts!  Good luck!

Regards 

[Massdog05]

Dustin,

That sounds close to what we will need, however, I am not sure that a digital pulse would be capable of triggering our device.  Correct me if I am mistaken, but previously we have been firing the electric match with a 3-5v battery.  Wouldn't this be an analog signal that we would need to output?

Thanks! 

[smercurio_fc]

You would really need to look at the current requirements. If it's some sort of match, my guess is that the current requirement will be greater than what a normal DAQ board could provide, and you would need some sort of amplifier.

[Dustin_D]

MassDog05,

Check this link out.  This will show you how to use an electric match with a digital I/O line.  Also, it's a pretty awesome way to use one! You'll probably require a transistor of some sort to source enough current from your battery.  You should, however, be able to use your battery in place of the power supply in the schematic.  Good Luck!

Regards,

[rex1030]

You could also use really small gauge nichrome wire to do the igniting. This is actually what is inside the resistor described in that document only you would be able to expose the wire directly to the chemical you wish to ignite. Make sure you have regular wire going to and from the nichrome wire by the way. When the nichrome wire is overloaded with current the entire nichrome wire will either glow red hot, melt, or vaporize.

We experimented with making high quality resistors and had some fun with overloading the wire. Even used it to electronically light fireworks a little safer that 4th of july 🙂

The resistors may be simpler depending on your application, but it sounds like you wont be able to cram resistors into your .22 shells without effecting your test results.