NAS for PLC program storage?

We use a combination of AB and GE PLCs and have 3 laptops that our electricians and engineers use for programming. One of my frustrations is that we usually don't know which laptop has the most current copy of the documentation. If we take out the wrong one and do an upload from the PLC, the comments could end up on the wrong rungs, making troubleshooting difficult.

So I've been trying to find a way to solve this problem. My first thought was to just buy a bunch of small USB pen drives and keep one in each cabinet with the current documentation for that machine. But then I started reading about network-attached storage (NAS) devices. Most of our newer machines have Ethernet-based PLCs and HMIs, so I'm thinking I could plug one of these NASs into the machine hub and map a network drive in Windows so that it would always be available when I'm hooked up to the machine with any laptop. I was specifically looking at this one from Linksys.

Has anyone done anything like this, or have any other suggestions about how to keep the documentation files current?

Network Attached Storage will work, if everyone remembers to save the revised file to the NAS drive. A disadvantage is that probably everyone will become addicted to the network drive, and will not also save a copy on the laptop ("Aw, come on, saving a file twice just doubles the workload, and for what?"). Then when the NAS fails, or gets disconnected, or the IT Deptartemnt decides to cut you off, then you are dead in the water not just for one machine program but for every program. In other words when you move back towards centralized storage, you are losing the fail-safe advantage that several stand-alone laptops provide. I can imagine a scenario: It is 2010, and a lightning strike takes out the NAS at the same time as the Number 1 Widget Machine. Frantically looking at old laptop files, you find the last one saved was in October, 2007, about a month after the NAS was installed....

Pen drives, memory sticks, or USB drives will work, if everyone remembers to save the revised file to the USB drive.

Saving to laptop hard drives on multiple computers will work, if you keep a simple paper log in the laptop storage cabinet, with columns for Name, Date, Machine, Laptop SN, Program Revised Yes/No. Each person is responsible for updating the log when returning a laptop. Then when you need to know the latest revision, look for the machine and laptop with the last revision date. This works where people normally check out a laptop for a shift. If they keep one a week it might be a problem.

The bottom line is: It is hard to eliminate the Human Factor when you try to use machines to fix things so that no one has to be responsible for anything important.

If your laptops on the floor have the ability to reach the NAS, then you can use the built-in Synchonization software in windows XP to keep the NAS up to date.

Where I work we have 3 laptops, each using the same set of files to edit the various PLCs. These laptops sync up at the start of the day when they are turned on, and at the end of the day when they are turned off (assuming they are connected to the network). I found this to be the simplest way to keep a standard, up-to-date set of files.

Lancie1 said:

The bottom line is: It is hard to eliminate the Human Factor when you try to use machines to fix things so that no one has to be responsible for anything important.

Click to expand...

That's essentially what I'm trying to do but you're right, you can't eliminate the human factor completely. And if the only copy of the program is on the NAS, then we're in danger of losing it. I might try the synchronization idea as suggested by Christoff.

What I do is make a 3.5" floppy disk file copy and a printed copy to keep in each machine. Works the same as the pen drive idea, only a little more archaic, but cheaper. If changes need to be made, the first thing I do is open the floppy disk file and work from that until I have made all of the changes necessary. After everything has been changed, save the file to the floppy and then save the file to the hard drive. This seemes to work great, but then, I am the only person who does the programming and/or changes.

Get one of these http://www.snapserver.com/snap/en-US/Products/hw/servers/ss410 and run it in RAID 1. Then implement a backup program of some sort (daily or weekly backups moved off-site, say a safe deposit box or similar) for the central server. I've got an older Snap server with an external drive expansion that has been running continuously for about 3 years now.

I've had two of the little LinkSYS boxes and they are pretty much garbage... fine for storing junk at home, but not anywhere near good enough for anything you want to be certain will be there next year (or week).

Despite what many here will tell you a single central file server with a routine backup is the best solution to your problem so long as nothing is ever stored on any other drive... don't let anyone store any program on their laptop, make sure everyone puts it on the central server, then you only have to backup one thing.

I do agree that you have to beware of IT when saving to a company server so at my last plant I setup my own server incorporating RAID and wireless connection.

Again, this was a situation where I was the only one with a laptop but made me feel better to have the files redundantly saved and the laptop synched with the desktop server. I basically had 2 identical machines with everything saved in redundancy.