07-02-2008 03:44 AM
07-03-2008 08:19 AM
Dear Mike,
The best way forward is likely to be investing in another PXI card that will allow you to produce a retriggerable pulse train – the card can be fairly simple, as long as it gives you access to a counter. You could then route the counter to the trigger line of the relay card via the PXI bus. This method purely uses hardware timing – so you can achieve high levels of precision.
You will also need to define a scan list. Once a pulse has been received your application will step through to the next item on the switch scan list (therefore making a new relay and breaking the one currently being used).
Search “scanning” in the LabVIEW example finder, and you will be greeted with plenty of helpful example VIs. I would recommend having a look at the “niSwitch Software Scanning.vi”.
>> This is all assuming that you have niSwitch installed <<
There is plenty of information on our website concerning creating scan lists and the use of the switch software.
What sort of timing specs do you require?? If you can afford to carry out the timing within software (so you can tolerate an error of, say, +/- 100ms) then you could use any old data acquisition card to read the 5V trigger, and to allow you application to produce a software trigger which can be fed to you relay board via the software trigger line on the PXI bus.
Just to confirm… there is no external triggering line. Triggering is exclusively carried out by routing signals through the back plane of the PXI chassis.
I hope this has been of some use to you,
Best wishes
07-04-2008 08:22 AM
07-11-2008 06:34 AM
Hey Mike,
Firstly, I apologise profusely for not getting back to you sooner. I have been away teaching for the past few days.
You have correctly interpreted my suggestion, although you have raised a very good question! Even though you are using a single relay you will need to implement some kind of scan list – there are 40 relays contained within the 2570 board, and so trigger lines could not be set up for each individual relay.
You should be able to create a workable scan list for a single item. If you are struggling with this, perhaps you could implement a scan list that switches between the relay you wish to open & close and a dummy relay. The dummy relay being one of the 39 unused relays within your module - interacting with this shouldn’t have any impact on your experiment.
Furthermore, there is plenty of information concerning scan list creation on the ni.com website.
Sorry again for the late reply, and thanks for your patience,
Best of luck with your application,
07-11-2008 06:40 AM
07-11-2008 12:20 PM