Is it worth using Industrial Digital I/O and DAQ instead of a standalone PLC?

[karthik9]

I wanted to know that   "Is it worth using Industrial Digital I/O and DAQ instead of a standalone PLC" such as Modicon for running some Motors, pressure sensors, actuators?

In particular what I wanted to know is that "If NI USB 6525,NI USB 6008(As this is the cheapest it would be less expensive to experiment) can be used as a replacement for Modicon"

The thing is that if we use other PLC's 2 codes would be necessary to be written. one for the PLC and the other for monitoring....

[Norbert_B]

You are mixing things here.

PLC (programmable logic controllers) are autarkic systems with, in most cases, very limited resources for "simple, but deterministic" tasks.

Your stated NI devices are measurement extensions for (most likely Windows based) PCs for data collection and manipulation. If you are not running a deterministic OS (called "real time system"), you will have quite some jitter in your software execution. So things like "control" are hard up to impossible to realize with that approach.

I think you should look into cRIO, which is NIs 'version of a PLC'. But to be honest: cRIO is much more expensive than standard PLCs, but it is by far more powerful. Having both a real time controller and an FPGA at hand gives you flexibility and computation power no current PLC can really catch up with. Just as the PLC, a proper implemented cRIO system is autarkic so it really can be a replacement.

Norbert

[crossrulz]

If doing control, especially if safety is of any concern, then avoid USB like the plague.  If you are doing really simple motor control for a small motor that doesn't really do much, then you could possibly get away with a PCI(e) card or two in your PC.  But, as was already said, you can't trust Windows to be deterministic.  I'm a huge fan of the cRIO system.  There is a learning curve, but it is a truely powerful system if done correctly.

[r_good]

I agree with the above.  They make some small controllers for simple control applications for around $1200.  If you can get all of your code to fit on the FPGA you can have deterministic monitoring and control with an eRIO and would need a simple windows UI for just that, UI not deterministic control, leave that to the FPGA.  Implement your state machine on the hardwre if possible otherwise cRIO is the ideal.

here are a couple links:

https://www.ni.com/en-us/support/model.crio-9075.html

https://www.ni.com/en-us/support/model.ni-9146.html