Laptop to PLC heartbeat

[LP123]

Hi everyone,

I have a task at work that I'm hoping someone will be able to help me find a solution for. Here is the background info: I have a laptop that is connected to a weld controller (Rexroth) and the sole purpose of this laptop is to collect weld graphs and store them on an external HD for future use. However, if the laptop is accidentally powered down, then the graphs are not collected. My task is to figure out a way to generate an alarm on the PLC (S7-300) if the laptop is powered down. I know a heartbeat is used for this purpose, but how can I set one up from a laptop then send it to the PLC? My first idea was to set up an OPC server on the laptop (kepware is my facility standard), but that seems like over kill for such a "simple" problem. Is there an easier way to do this? Has anyone done something similar to this? Any thoughts/ideas are appreciated.

Thanks!

 

[drbitboy]

What protocols are available to connect the laptop to the PLC? For example, how does the laptop "collect weld graphs" (data?) now?

 

[Eradicated]

How about using a USB watchdog card with a built-in relay? I have used PCI watchdog cards in the past to monitor a process on the PC, so if the process failed the relay would get de-energised.
You can then wire the relay into a standard digital input in your PLC.

 

[Steve Bailey]

Does the PLC attempt to send the data to the laptop when fresh data becomes available or does the laptop request data?. If the latter, what triggers the laptop to issue the request? If the PLC initiates the data transfer, you will need to add an acknowledgement from the laptop. A failure to acknowledge the the PLC's attempt to send the data will trigger the fault. If the laptop is in control of the communications, you will need to have it periodically increment a tag in the PLC and if the PLC doesn't see the value change within a reasonable time, it triggers the fault.

 

[robertmee]

How about using a USB watchdog card with a built-in relay? I have used PCI watchdog cards in the past to monitor a process on the PC, so if the process failed the relay would get de-energised.
You can then wire the relay into a standard digital input in your PLC.

What I was going to recommend. I've used them for a medical device cart to power down a laser if the controlling PC is shut off.

 

[drbitboy]

What protocols are available to connect the laptop to the PLC? For example, how does the laptop "collect weld graphs" (data?) now?

AdvancedHMI might be a possibility.

 

[LP123]

What protocols are available to connect the laptop to the PLC? For example, how does the laptop "collect weld graphs" (data?) now?

The laptop to PLC connection will be profinet (its not currently setup at the moment?. It's a local ethernet ip connection to the Weld controller.

 

[Steve Bailey]

The laptop to PLC connection will be profinet

Then the PLC will know when it is not communicating with the laptop. There will be a status word.

 

[LP123]

How about using a USB watchdog card with a built-in relay? I have used PCI watchdog cards in the past to monitor a process on the PC, so if the process failed the relay would get de-energised.
You can then wire the relay into a standard digital input in your PLC.

that's a good idea, I can get one cheap off amazon. Thank you for the idea!

 

[I_Automation]

How about using a USB watchdog card with a built-in relay? I have used PCI watchdog cards in the past to monitor a process on the PC, so if the process failed the relay would get de-energised.
You can then wire the relay into a standard digital input in your PLC.

Knowing how operators in factories love to alter and play with things to get more production bonuses while sacrificing quality, wouldn't they be able to put the USB watchdog in any device and not just the laptop doing the charting?

Also, if it's wired to a PLC input then it would have to be unplugged and stay at the machine if the laptop is taken elsewhere.

My suggestion is a dedicate logging computer in the control panel. A fanless PC can be bought for $49, used laptops for $89, 2TB USB SSD for $39

 

[AlfredoQuintero]

The laptop to PLC connection will be profinet (its not currently setup at the moment?. It's a local ethernet ip connection to the Weld controller.

CoDeSys for Windows has a PROFINET IO device that can be configured as a PROFINET IO device under the Siemens, but the license will set you back several hundred Euros. On the other hand, it would allow to do a lot more than the heartbeat application.