Siemens S7-1200 relay problem

[Israelsson]

I have problem with hanging relays in S7-1200 main CPU unit.
After a couple of weeks on and off (30sec)with a small load my outputs starts to hang.
I have seen this on my two instalation and it looks like bad quality on the used relays in the CPU.
My load is a EXx saftey barriar 9176 fron Stahl, data sheet added to the thred.
Cant see any reason for this problem, please help?

 

[Israelsson]

Data sheet Stahl 9176

 

[RajeevCell]

S7-1200 CPU comes with transistor outputs, not relays. What is the complete part number of your CPU?

Are you turning on/off the relays using any counters? If so, then check if the counters are reaching their maximum values.

 

[Israelsson]

The CPU is 1214C DC/DC/Relay.
My load is non inductive and only 60mA
On and off 30s,
starts to get problem after a couple of week usage

 

[Skogsgurra]

Cable length? Those rather tiny relays can't take much capacitive loading before they weld. You may need series resistors to reduce the charging current.

BTW: Is it Johan?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Israelsson]

Yes its Johan
Im using a safty barrier directly connected to the PLC.
EXx ia

 

[Israelsson]

Siemens asked me to add diods, cant see any reason its not inductiv load....

 

[Skogsgurra]

Well, you know Siemens, Stockholm...

Where are your systems? Anywhere near me?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Israelsson]

Boden and Norrköping
Do you still have skype

 

[Skogsgurra]

Yes, but I have mixed up skype names and computers. I don't know any more if it is Skogsgurra, Skogsgurra1 or Skogsgurra11. But my phone number is on our home page. So is the e-mail address.

I will visit Braviken soon. Is that where your system is? I have just bought a fast contactless current probe (5 MHz 10 mA-20 A) that may come in handy.

I can pop in and have a look when I go there. Won't cost you a dime - but you'll have to buy me lunch or dinner.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Israelsson]

Deal
Give you a call tomorrow
/Johan

 

[Skogsgurra]

OK.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.