7 posts in this topic

Good day fellow PLC ninjas!

I have a question/ concern which I would love your opinions on. We have 3 FX3U PLC’s+ENET cards. Two of the 3 PLC’s move around in an EMS trolley. The other is a ‘base station’ with a GOT2000 connected via Ethernet.

Base PLC IP = 192.168.1.11

HMI IP = 192.168.1.31

Carrier 1 IP = 192.168.1.61

Carrier 2 IP = 192.168.1.62

I have programmed the base PLC to use Active communication; we are using fixed buffer communication to send and receive data to/ from the Carriers. The carriers are set up as Fullpassive ‘slaves’. This part works well and the update time changes (using a counter in the base station) from 1s to 100ms (because it enters a different work station). 

My issue is the following: using a network sniffer (WireShark), I pick up plenty of re-transmits and sequence number errors coming from the base PLC’s ENET card. This is troublesome and causes delays when the update time is required to be fast (100ms). I am sending and receiving 10 words of data. The wifi seems stable, and there is minimal noise in the area. The power has been turned down and the antennas used are suited well for the application. The antennas are at a similar height to minimize possible loss of signal. I have LOS (line-of-sight) to the carriers at all times; to at least one of the antennas (I am using 802.11n).

Has anyone picked up issues or found settings which can be used for comms over wifi?

I can easily do this using a S7-1200 Siemens PLC and have done so using 12x S7-1200 clients and 2 AP’s with 1 base PLC. I have also successfully done this using 8xFX3U client with a System Q base PLC.

My suspicion is that the delay in reading and writing to/ from the BFM in the ENET card is causing this. I am not sure that if I change to a FX5U will help. The communication cards on the Mitsubishi PLC’s seem very limited.

Does anyone have any technical details on the access times between the CPU and communications cards’ BFM?

Help is as always, appreciated.

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Hi Wayne

Well, first off unlike the FX3U where you require a card to do fixed buffer memory (FX3U-ENET) with the FX5U with the build-in Ethernet port, you can do fixed buffer memory directly on the PLC block. So the change of errors is nearly none and if you look at what you are getting with the FX5U (16 in and out, 2 Analog in, 1 out, build-in Ethernet and serial comms), it is actually better than the FX3U where you still require an additional FX3U-ENET unit.

PS - Adroit Technologies are currently running a promotion on FX5U. Not sure if you know about it, but maybe give them a call. 

Moenie skaam wees nie. Sal so ver moontlik probeer help.

 

 

 

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Curiosity question and off topic.

Does EMS stand for emergency medical services like it does in the US?

If so, are there no HIPA, (privacy),  concerns with using wifi to communicate with these carts?

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Never mind. I just talked to my wife who works IT at a hospital and they run all their stuff off wifi. 

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Thank you for the replies.

We had a look at replacing the FX3U with the FX5U; but there is no stock available... Our time was limited so we decided to use an Omron 1-wire communication instead. 

I have come to the conclusion that the Mitsubishi FX3U PLC simply is not designed to operate reliably over wifi or even fixed Ethernet. It is disappointing to see this as I have been a huge Mitsubishi fan for a very long time.

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my point of view fx 3u is better 4ever  because fx3u support all functions transfer speed is more efficency in fx5u and fx5u is very slow online communication monitor and change take more times . fx3u enet module u can open 8 ports ..

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On 7/26/2017 at 8:52 AM, Daran said:

my point of view fx 3u is better 4ever  because fx3u support all functions transfer speed is more efficency in fx5u and fx5u is very slow online communication monitor and change take more times . fx3u enet module u can open 8 ports ..

I love these little CPU's for their awesome instructions and the speed at which one can develop; but, when it comes to comms, it is a bit lacking. 

We tested this situation with a FX5U and the issue went away. I assume that the bus between the cards is faster in the newer CPU's. It is a pity that you are disappointed with the FX5U; will have to do a few experiments myself first.

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