writing software for a hydrolysis rocket thruster

[HydroRocket]

To whom it may  concern,  

I am a Midshipman at the United States Naval Academy and am currently working on an aerospace engineering project that entails building a rocket which produces thrust from igniting the oxygen and hydrogen produced  from the hydrolysis process. Myself and another classmate have built the entire setup of the rocket and have everything connected to separate oxygen and hydrogen tanks as of now.  However, we are currently in the testing phase and are trying to automate the data acquisition of a test run.  The basic background behind our task is being able to start a program which begins collecting data from pressure transducers (located at various points along our lines), opens 2 solenoid valves (1 for the oxygen line and 1 for the hydrogen line) , and after a certain amount of time (say around 5 seconds) closes the valves so the motor no longer burns.  There may be a few more steps, however we would like to at least have this as a starting point.  We are using LabVIEW  
and have the following NI parts:

NI cDAQ-9174
NI 9219
NI 9481

Neither of us have ever used LabVIEW before and we are having a great deal of trouble trying to figure out how to make this work.  Our pressure transducers are rated at 20mA and 36V.  Also we are using 115V solenoid valves with a max of 8W.  Any help or insight you could provide would be greatly appreciated. Thank you very much for your time.

Very Respectfully,

Chase Rogalski
MIDN           USN

[smercurio_fc]

Well, I have to admit that sounds like a fun project. It sounds like you have an open-loop system. You're basically collecting data, opening valves, and then closing the valves. Presumably you're always collecting data. Is there a specific time after you begin collecting the data that you open the valves? Is the "test run" the start of the data collection to the closing of the valves? Do you still collect data after the valves are closed?

As for the LabVIEW code itself, what are you having trouble with? Have you taken a look at the DAQmx examples that are installed when you install DAQmx. Or, are you using the DAQmx Assistant? What kind of file are you trying to save?

[lmtis]

If I lived anywhere near Annapolis I'd be happy to stop by to offer my services as a tutor, that does sound like a fun project.  The DAQ chassis you have is fairly easy to use with DAQmx.  Open the LabVIEW Example Finder and look under Hardware Input and Output > DAQmx > Digital Generation and DAQmx > Analog Measurements.  That would be a good starting point.  This is a good place to come back to if you have any specific questions, plenty of folks ready to help out.

[Been bitten by LabVIEW]

Fun... and deadly. 😞

A

[NIquist]

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@Been bitten by LabVIEW wrote:

Fun... and deadly. 😞

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I'll bet they all know NOT to stand in front of the part where the fire comes out.

[mikealder]

Please ensure you fit a twin poleEmergency Stop switch inbetween the outputs of the 9481 and the solenoid valves, you need to be able to quickly shut this down in the event of the PC crashing while the solenoids are open and the PC is running Windoze.... - Mike

[Been bitten by LabVIEW]

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@NIquist wrote:

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@Been bitten by LabVIEW wrote:

Fun... and deadly. 😞

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I'll bet they all know NOT to stand in front of the part where the fire comes out.

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Yeah, they stand in front of the pointy end. 😄

[HydroRocket]

There is no specific time after we begin collecting data that we would like to open the valves. However, we dont want to wait a very long time since we are concerned with collecting the data and not just getting a great deal of steady state information.  The test run encompasses everything from the start of the data collection til the valves are closed and possibly a second or two of data collection after all the valvles are closed just to see how much pressure is left within the lines after the burn.  For the LabVIEW portion we seem to be having the most trouble with actually putting the block coding together and getting a working program from start to finish.  We were able to use Labview to open and close the solenoid valves, and also take a reading from the pressure transducers.  However, we accomplished this on an individual basis and we are not sure how to string everything together.  We have worked a great deal with MATLAB coding but the block coding is very new to us.  Also we took a look at the examples, but at the same time we are having trouble understanding what is actually happening in the examples and how all processes are put together in a certain order.  Im not 100% positive on the type of file we are trying to save but I believe our best bet would be just to go with an excel file that logs all the pressures. 

[smercurio_fc]

Can you upload the code you've already put together, or is there a government restriction on doing so?