Time Sync for ControlLogix (using PTP) ?

[slick_william]

Hello all,


We have a customer with about 10 PLC's which they want to synchronize the time (TOD, date, etc). These are mostly 1756-L82's with 32.014 firmware.

The customer has a central time server which can broadcast the time via NTP (Network Time Protocol) and possibly PTP. However with PTP, traffic is a concern as it seems to update/sync the time incredibly often and add tons of traffic to the network.

We have been looking at the 1756-TIME module, but this customer currently does not have one and would prefer to message the time server directly (if that's even possible?) vs. having to buy new equipment.

Questions:

1) If in fact the customer's time server can respond to PTP time requests, would it be possible to use PTP to sync up these PLC's? The idea was to have one PLC message the time server, then have all the other PLC's message the master PLC to sync the time.

2) If it IS possible to use PTP as mentioned above, is it possible to only poll the time when we want to sync it (as opposed to having it constantly sync at all times continuously)? I am thinking of something like "if time of day = 8 am then ... initiate MSG / open socket to time server and sync..."

3) Or would it be easier / less headache to just buy the 1756-TIME module and use that? This thing looks expensive as hell and all it does is synchronize time? (I'm in the wrong business, should have went into designing industrial time sync hardware)

Thanks all,
Slick

 

[JeremyM]

PTP traffic is no more a concern for traffic than anything else. Participating nodes continuously update and you won’t be able to implement it using periodic messaging - that would just defeat the protocol’s purpose. It’s designed to keep drift/skew minimized, after all.

You can guarantee a particular grandmaster by setting its Priority 1 lower than the others. If its Priority 1 is matched with another node, Priority 2 is used as a tie-breaker.

NTP can also be implemented using the controllers’ Socket CIP object and there’s sample code available to do so.

 

[Ken Roach]

Do these controllers run CIP Motion applications on Ethernet ?

How closely synchronized do they have to be ?

Can the customer use the Logix 5000 Clock Sync Tool on a server to periodically update the Wall Clock Time ?

 

[aawilliams85]

What is the end goal of trying to synchronize the times across these controllers?

I've generally avoided doing any kind of manual/external time synchronization in systems using CIP motion over ethernet. However, for display and alarming purposes, it is still convenient to have a real-world clock, so I've been using my SCADA system to write the current date/time to some tags in each PLC, and have the HMI (PanelView Plus 6/7) use those tags for clock sync periodically.

 

[slick_william]

Thanks all, good information.

The intent is to synchronize all target PLCs to within a few seconds of each other. The process is water/wastewater so exact synchronization (and minimization of skew as was mentioned) may be overkill in this case.

Given the comments so far, I think I would be leaning toward using NTP with a socket CIP object as one poster mentioned. I had heard though that it was impossible to do this without the 1756-TIME module.

I'll look into it more on my end. If I can set up that sync using their existing NTP server would be ideal.

To Ken's comment, I think the Clock Sync tool would work if it could synchronize with their existing NTP server.

Thanks again and talk to yall soon

S

 

[James42005]

"To Ken's comment, I think the Clock Sync tool would work if it could synchronize with their existing NTP server."

Clock Sync Tool is no longer supported. I think you can still download and install it but you wont get any support. If i remember correctly, the reason its not supported anymore is because it can be a potential security risk due to the way it works.

We used to run ours on our Dev station, had sync schedules setup. I dont believe it would allow to sync any controllers that had motion, for good reason obviously. It worked great for us for years, main goal was time sync for alarming and some logging. However, when we moved our dev machine to a windows 10 environment the sync tool quit working, very buggy, wouldnt sync, etc... and again... no support from rockwell so since its not critical for us, we just sync everything manually twice a year at DST or when an operator asks us to.

Sorry i dont have any experience in the other solutions other than doing the same research your doing now. My plant didnt see the need the to spend money on time sycnchro. Good luck

 

[Rayman_7676]

In case anyone is still having issues with trying to sync the time on multiple PLCs from a server I have found a solution using Rockwell Software, no license is required. All you need to install is 6.4 FT Services and then 1.0 FT Action Manager on the server with a connection to the PLCs. Define connection path in FT Linx (IP). Then in FT Action Manager you can create a Trigger - (Time Interval) Action - (Wall Clock) Then link the two with a Task. It is pretty straight forward, but I think there was one reboot during install. This runs as a service. Hope this helps.