We have a conveyor system with a Siemens S7-317 2DP with 3 DP/AS-i Link gateways (6ES7194-5AA00-0XA0). At one of the gateways we are getting the “AS-i Power Fail” led flicker.

The AS-i bus PSU is an IFM AC1206 (http://www.ifm.com/ifmuk/web/dsfs!AC1206.html).

The AS-i network from this gateway daisy-chains out to approx 20 nodes of IFM AC2701 (http://www.ifm.com/ifmuk/web/dsfs!AC2701.html).

At node 3 we have an isolator auxillary input on I+ and I1 and an IFM OC5230 (http://www.ifm.com/ifmuk/web/dsfs!OC5230.html) on I+, I- and I3 via wires 1, 3 & 4 of the sensor. This sensor and cable have been renewed to rule them out.

The DP/AS-i Link indicates “Slave 3” flashes the AS-i Power Fail led. We have seen the IFM PSU power led flicker which led us to renew it with a new IFM AC1208 (http://www.ifm.com/ifmuk/web/dsfs!AC1208.html) which just seem to freeze the DP/AS-i Link. This happened when we tried another AC1208. We tried a known-to-be-working AC1206 from one of the working gateways on this system which worked. The PSU is set to 115vac. This supply is constant.

The AS-i node has been renewed along with the DP/AS-i Link. The cables have been checked out between nodes - SY cable not yellow AS-i cable - the inputs to this node 3 have been disconnected which stops the fault. The fault only occurs when we have the OC5230 connected. We tried another sensor but after an hour or so the fault re-emerged. Without this sensor connected to this AS-i node the network is fine yet the system has been running previously without a hitch. The voltage at the node is a constant 29.6vdc.

Can anyone point me to something I may be missing or have overlooked, please?

Thanks in advance.
s.f

Hi Silva
I will pass this onto Paul Hingley of SIEMENS for comment. However as the slave and Power Supply are IFM (not UK members) what have they advised?

Regards Derek

Thankyou, Derek

Regards
Richie

We have seen instances of a faulty node taking the whole bus out. I’m sure you’ve tried swapping the AC2701 with a unit from another manufacturer or a known good one, though you don’t mention it?  Failed units oftem come in batches!

Jon

Thanks for your reply, Jon.

All the info is in my original post. Paragraph 4 states the renewal of the sensor / cable, paragraph 5 states the renewal of the PSU and paragraph 6 states the renewal of the AS-i node (a newer version) and gateway. The thing that bugs me is when we tried a larger PSU the fault did not clear at all yet it cleared for a short while (from a couple of minutes up to an hour) when the smaller one was refitted, and when the known working small one was fitted too. Is the use of the larger PSU telling me something?

Thanks again for your time.

Regards
s.f

One last thing then. Does your machine have an inverter-driven motors or servos? You could have an EMC issue - I’ve certainly seen plenty of those! But there are ways around.

Jon

Thanks. Really useful!

Thanks for your suggestion. You can also use the instances of a faulty node taking the whole bus out. I’m sure you’ve tried swapping the AC2701 with a unit from another manufacturer or a known good one.