Voltage ramp + hold

[Thibault_Prevost]

Hi,

I'm using Labview 8.2.1. I'd like to output to a motor an analog voltage whose profile could look like: 1) ramp from V-start to V-end @ Vspeed 2) hold V-end for t seconds 3) ramp back down to V-start @ -Vspeed. I'm new in the Labview world and I followed one of your recommendations from the many forum posts dealing with the topic. The vi I have now (see figure attached) is very basic and does only partly take care of the first ramp phase - not even mentioning the last 2 phases... The main big concern I have with these while/timed loop iterations, is that 1)  the number of iterations as well as the voltage step magnitude do not seem to change whatever value I plug in for the iteration increments (varying them from 10E-10 to 0.1...) and 2) that it does not allow me to start from an arbitrary voltage level or to program phases 2 (hold) and 3 (ramp back)... Is there a way to work around this using arrays for instance? If so, how would I implement that? I've been through your introductory courses on-line but it did not help that much.

Thanks for your help!

Thibault.

[Ray.R]

I just quickly read your post. (just taking a very quick break).

Suggestion:  breakdown the three sections into number of steps. 

Define number of steps for ramp up, number of steps for hold (constant level), and number of steps for ramp down.

Add the three sets of steps and that will give you the total of iterations.  Then you can figure the increment size based on max level divided by steps ramp up, and do the same for ramp down. 

You could use a For Loop and shift registers...  Maybe during my next break, I can do a small example..   But the above should get you going..

RayR

[Ray.R]

You are looking for something that would generate a ramp like the picture below, right?

I wrote the code extremely fast and I'm kinda ashamed of posting the code. 😉

Message Edited by JoeLabView on 12-18-2007 07:49 PM

[Thibault_Prevost]

Thanks! This looks indeed exactly like what I'm looking for
If you didn't mind emailing me the code (prevost@mit.edu), this would be great. Otherwise, can you explain to me how these three sets of steps work? Do I need to add 3 while loops? Also, can the signal be output as a voltage to a given device?
Thanks again!

Thibault.