Start and Stop Trigger

[pankaj mohan]

Hi, I've this silly problem going on for quite a while now.I just cannot
figure out the solution. May be somebody can help.

I am using LABView 5.1. I wish to incorporate a start and a stop trigger
on my VI. If the force value goes above a certain level, it has to start
aquiring. This sounds simple can be done by a simple analog trigger. Now
I want to stop the acquistion once the value is below that same level.
How do I go about doing this?

Thanks in advance !

Pankaj

[bubucis]

Some cards just can't do it. See your cards specs. usually they brag about
start-stop triggers. Other option is to gate the i/o instead of triggering,
that also depends on the hardware. You can also build a simple flip-flop
circuit to give you start-stop signal. Also you can monitor the trigger in
software on the second channel and then stop your VI.
"pankaj mohan" wrote in message
news:3818F523.964C8A1F@netscape.net...
> Hi, I've this silly problem going on for quite a while now.I just cannot
> figure out the solution. May be somebody can help.
>
> I am using LABView 5.1. I wish to incorporate a start and a stop trigger
> on my VI. If the force value goes above a certain level, it has to start
> aquiring. This sounds simple can be done by a simple
analog trigger. Now
> I want to stop the acquistion once the value is below that same level.
> How do I go about doing this?
>
> Thanks in advance !
>
> Pankaj
>

[abrause]

I have attached a vi that triggers an event when a voltage reaches a certain
threshold
but "never again", even if the voltage subsides and then rises to the
threshold on
subsequent occations.
Perhaps this vi could be modified to do what you need. The description for
this
function was presented on Info-Labview but I've misplaced the authors name.

Alan Brause


pankaj mohan wrote in message
news:3818F523.964C8A1F@netscape.net...
> Hi, I've this silly problem going on for quite a while now.I just cannot
> figure out the solution. May be somebody can help.
>
> I am using LABView 5.1. I wish to incorporate a start and a stop trigger
> on my VI. If the force value goes above a certain level, it has to start
> aquiring. This sounds simple can be do
ne by a simple analog trigger. Now
> I want to stop the acquistion once the value is below that same level.
> How do I go about doing this?
>
> Thanks in advance !
>
> Pankaj
>



[Attachment Clever Single Event Trigger.vi, see below]

[Harry King]

In article <3818F523.964C8A1F@netscape.net>,
pankaj mohan wrote:

>I am using LABView 5.1. I wish to incorporate a start and a stop trigger
>on my VI. If the force value goes above a certain level, it has to start
>aquiring. This sounds simple can be done by a simple analog trigger. Now
>I want to stop the acquistion once the value is below that same level.
>How do I go about doing this?

It sounds to me like the best way of doing this would be a true/false
node (aka case node, I believe). Write your aquiring code in the true
node, and a null in the false node. Send a conditional controlling the
node.

Give that a shot. I use it for something that (I think) is similar. I
take a reading every 10 seconds. When my timer hits 10 seconds, my node

turns true, and it sends one reading to a spreadsheet. It doesn't do
anything while false.

If you have any problems, feel free to e-mail me.

Harry

--
"Little Joe for the Big Heisman, '99"

[pankajmohan@my-deja.com]

Thanks Harry:

Couple of things thats bothering me with this method is the time lag
and abundance of data. My acquisition is in KHz on one board. And when
this Khz board kicks off, it is also suppose to kick off the
acquisition on the other board, and for this "other board" we are
talking about acquisition in MHz. I don't think the scuzy HD on my m/c
can handle this abundunt data. There has to be some way that will ask
the boards to stop doing anything whatsoever when the conditions are
false.





In article <7vckac$5e8@catapult.gatech.edu>,
hk16@prism.gatech.edu (Harry King) wrote:
> In article <3818F523.964C8A1F@netscape.net>,
> pankaj mohan wrote:
>
> >I am using LABView 5.1. I wish to incorporate a start and a stop
tri
gger
> >on my VI. If the force value goes above a certain level, it has to
start
> >aquiring. This sounds simple can be done by a simple analog trigger.
Now
> >I want to stop the acquistion once the value is below that same
level.
> >How do I go about doing this?
>
> It sounds to me like the best way of doing this would be a true/false
> node (aka case node, I believe). Write your aquiring code in the true
> node, and a null in the false node. Send a conditional controlling
the
> node.
>
> Give that a shot. I use it for something that (I think) is similar.
I
> take a reading every 10 seconds. When my timer hits 10 seconds, my
node
> turns true, and it sends one reading to a spreadsheet. It doesn't do
> anything while false.
>
> If you have any problems, feel free to e-mail me.
>
> Harry
>
> --
> "Little Joe for the Big Heisman, '99"
>


Sent via Deja.com http://www.deja.com/
Before you buy.

[Labview user name]

Use the analog trigger on the first DAQ board and trigger the second board
using the Route.vi and a pfi line out to the digital trigger of the second
DAQ board. It works quite well and it is easy to pre-trigger the second
board if needed. The timing is flawless.

A few notes:

1. The NI manual (at that time) had the incorrect usage of the route.vi.
Use the device number in place of the Task id.

2. Do not use parallel while loops. Nest both reads in the same loop.

3. Windows NT is much preferable to 95/98 for this sort of thing.

4. Avoid extraneous devices such as network cards and sound boards. They
clog the bus.

pankajmohan@my-deja.com wrote in message <7vcs4a$7e8$1@nnrp1.deja.com>...
Thanks Harry:

Couple of things thats bothering me with this method is the time lag
and abundance of data. My acquisition is in KHz on one board. And when
this Khz board kicks off, it is also suppose to kick off the
acquisition on the other board, and for this "other board" we are
talking about acquisition in MHz. I don't think the scuzy HD on my m/c
can handle this abundunt data. There has to be some way that will ask
the boards to stop doing anything whatsoever when the conditions are
false.





In article <7vckac$5e8@catapult.gatech.edu>,
hk16@prism.gatech.edu (Harry King) wrote:
> In article <3818F523.964C8A1F@netscape.net>,
> pankaj mohan wrote:
>
> >I am using LABView 5.1. I wish to incorporate a start and a stop
trigger
> >on my VI. If the force value goes above a certain level, it has to
start
> >aquiring. This sounds simple can be done by a simple analog trigger.
Now
> >I want to stop the acquistion once the value is below that same
level.
> >How do I go about doing this?
>
> It sounds to me like the best way of doing this would be a true/false
> node (aka case node, I believe). Write your aquiring code in the true
> node, and a null in the false node. Send a conditional controlling
the
> node.
>
> Give that a shot. I use it for something that (I think) is similar.
I
> take a reading every 10 seconds. When my timer hits 10 seconds, my
node
> turns true, and it sends one reading to a spreadsheet. It doesn't do
> anything while false.
>
> If you have any problems, feel free to e-mail me.
>
> Harry
>
> --
> "Little Joe for the Big Heisman, '99"
>


Sent via Deja.com http://www.deja.com/
Before you buy.