Use angular Encoder position to trigger Digital out

[ngio]

Hi,

I am a beginner labview user, I have access to three modules, two NI9201 and one NI9401.

I have an angular encoder that is used to measure the angular position of a motors crankshaft, what I'm trying to do is use the encoder to trigger a digital out (spark event in the engine) at a certain angular position.  For example, I would like to trigger at top dead center (or 0 degrees on the encoder), then I want to be able to change this to +5 degrees on the encoder, etc. 

So far I am able to read in the angular encoder when the motor is running, I am also able to output digital out signals although I can't find a way to link the two together.  

If anyone has any idea how to do this, it would be greatly appreciated, I have attached my VI.

Thanks in advance,

Nick

[Bill_5335]

Can you save your current VI for a previous version?  (i.e. 8.5)

I can't open your VI with v 8.5.

Thanks,

Bill

[ngio]

Hi Bill,

Here's the earlier version (8.5).

Nick

[Bill_5335 · Accepted solution]

Hi Nick,

I hope the attached vi will get you on track.  It's just a general concept.

The while loop will run until you hit the stop button.

   I take it you will need one spark per revoultion.

This VI is really just an If/Then

   If the encoder value is equal to (in this example ) zero,

   Then trigger the digital output.

I know I have a broken wire, but I didn't know how to get the angular position from you DAQmx.

Let me know if this help. (Also let me know if I'm off target)

Good luck,

Bill

[ngio]

Hi Bill,

Yes the concept you provided was exactly what I needed to do, it all seems easier now that I've seen it.

So I have implemented the concept and got a working function, now I am wondering if there's any way to do it faster.  I am trying to trigger the spark for the engine and the fact that I have to stop tasks every spark iteration slows my sampling down tremendously.  If there's any way you know that can do this without start/stop task blocks I would be very interested.

Thanks Again for the help,
Nick 

[Bill_5335]

I'm not that familiar with start/stop tasks.

Can you place the start and dtop outside of the while loop?

   For example, start your task before the loop and stop after you exit the loop?

Bill

[ngio]

I'm afraid not, this is the only way the task can be performed(I.e. The task must be stopped before it's started again). I will work with it a bit more and see what I can come up with.

Thanks again for the assistance.