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CAN-BUS

Thread Starter: Rodrigo N.   Started: 10/28/2009 8:14 PM   Replies: 15

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  10/28/2009, 8:14 PM
Rodrigo N.
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Hi people!

I need to control an engine and a transmission that uses dual channel CANBus protocol, for redundancy (CAN1 and CAN2, both with the same signal).
I was thinking about using a gateway to transform PPI to CAN to control both, but they have 2 channels.
Anyone knows any solution to solve my problem?

Thanks in advance,

Rodrigo
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  10/28/2009, 11:43 PM
J_Bell
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Dear Rodrigo,

I am sorry, I do not know any solution for the S7-200, but the S7-300 and S7-400 get some interfacing by 3rd party nodes... Some companies provide CAN Bus interfacing... just check the Internet for more information about it.

If some S7-200 specialist has any idea... i would apprechiate to know more about it.

Best regards
J_Bell
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  10/29/2009, 3:11 AM
Rodrigo N.
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Hi J_Bell!

I`ve found an gateway that works with PPI to CAN:

http://www.renuelectronics.com/pdfs/letter/gwy-300.pdf

The huge problem is that there are two channels CAN to redundancy. I don`t know how can I compare both signals with PLC to choose one of them and detect defect in one of the channels.

Thanks,

Rodrigo 
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  10/29/2009, 2:37 PM
J_Bell
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Hello Rodrigo,

well, I do not know this device but if it fills your requirements... OK.
The S7-200 has one PPI Port and one Free-Port. So you will have to decide for yourself where you want it to be connected to. The problem with redundancy, at least in my eyes is to decide which data is right and which one is wrong. Solving such issues requires a lot of technology... usually.

Maybe you post how you want to decide which one of the received Data is right and which one is wrong.

I look forward to see this.

Best regards
J_Bell
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  11/4/2009, 1:55 PM
Rodrigo N.
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Hi!!!

I will try to keep using Siemens PLCs, cause we`ve already the Step 7 software, Simatic Field PG and a bit of practice with these PLCs, so I think that would be cheaper to keep with it.
I would like to know if is it possible to implement the architecture of the file that is attached in this message, to have a physical redundant bus.

Thanks,

Rodrigo

Attachment: Architecture.JPG  (8 Downloads)
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  11/4/2009, 2:57 PM
J_Bell
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Dear Rodrigo,

I would say the left side, until the Gateways, should work. But I do not know how the CAN Bus will work with it... and how it reacts. I do not even know how the Gateways will work... but if I imagine that theses Gateways provide only some data... the S7 side would be OK.

By the way... how will you ensure the redundancy in this case?

Best regards
J_Bell
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  11/4/2009, 5:42 PM
Rodrigo N.
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Hello J_Bell!

Unfortunately I don`t have any experience with CANBus and Gateways yet, but I will try to make it works.
I was thinking about using information of only one channel most of the time, but send information to both channels at the same time.
If I had a time out in the channel that I was using, I would change to use the informations of the other channel.
Do you know if is it possible to implement?

Best Regards,

Rodrigo

   
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  11/4/2009, 11:23 PM
J_Bell
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Dear Rodrigo,

I have to admit I can not tell you that it works... I do not know.

The issue is, I do not know how the CAN Bus will handle this situation. I fear you will have to talk to a CAN Bus specialist about it... I do not know if a CAN Bus node is able to handle instructions by two differnet stations. If I see it on PROFIBUS DP side I know that it does not work... with PROFINET IO it should work but specificly only for certain IOs mapped to certain Controlers... but this is not working till now... at leased not as far as I know.. So, I do not know if it works with CAN Bus, personally I doubt it... but I do not know. I am sorry. blush

Best regards
J_Bell
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  11/6/2009, 1:36 PM
Rodrigo N.
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Hi!

Leaving the redundant CANBus aside, do you know if is it possible to implement the architecture anexed or something like that?
 
Thanks,

Rodrigo

Attachment: Architecture2.JPG  (3 Downloads)
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  11/6/2009, 1:44 PM
J_Bell
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Dear Rodrigo,

the question is, how many PROFIBUS interfaces does the Gateway carry? If it is one, I would say no. If it has two independent ones for redundancy I would say it is worth a try. (Because I do not know if this Gateway supports the redundancy the SIMATIC uses.)

Best regards

J_Bell
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Rodrigo N.
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