This is my 2nd post here.

After scan thru some of the post here , i notice PC base control is more accepted compared to 8 yr ago.

I can see that both PC and PLC control have their own application. for example for small I/O application is it cheaper for PLC. and for large application with motion, and c/w HMI , Ethernet access. PC control will be more suitable.

Can some one give what other reasons why PC base is more accepted now ?

paul yeo

 

That's easy, price out what you have to do with a PLC to do networking, databases, barcode readers and all the other things that are add-ons to the PLC paradigm. As things get more and more connected, it becomes much easier and much cheaper to add PLC capability to a PC than it is to add PC capability to a PLC.

Actually, big automation is solving the problem by making odd shaped PCs and calling them PLCs, but maintaining markups that keep system prices high. On some large projects the price differential would pay for someone to write a PLC add-in from scratch. I suspect this is how some of the "soft PLCs" came into being. What isn't being addressed and presents an opportunity, is what separates a mainframe from a powerful PC. The mips may be the same, but the difference in IO capability is dramatic. With the right architecture, a PC class processor could easily run a whole plant.

As long as it wasn't running Vista.......:^)

Regards
cww

 

"More accepted" is probably too strong a term. It might be better to say that people are less afraid of PCs today than they were in the past.

As for cost, if all you want to do is save some money on PLCs then have a look at using a different brand of PLC. The applications that you cite for "motion, and c/w HMI, Ethernet access" are things that many modern small PLCs can often do reasonably well, although their Ethernet access capabilities may be weak.

Where a PC has an advantage is with things like sophisticated data acquisition, mathematical processing, logging results in a database, and
communicating those results to the rest of the company. A PC can deal with more data and do more things with the data.

If I was asked to design the control system for a new project, I wouldn't start by asking "where can I use a PC?". On the other hand, if the application would genuinely benefit from using one, I wouldn't be afraid to use a PC either.