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dreamweaver1408
New User
Joined: 10 Mar 2009
Posts: 2
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| Mar 10, 2009 8:30 am |
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Hello,
I am having communication problems on a RS 485 data line. I have checked the cable and all is connected as should be.
However there are unfortunately other cables nearby (mains cable, loudspeaker etc) which might interfere with the data line.
I read about choke coils & ferrite rings but it seem be that there are different makes&models. Can you recommend any specific choke coil / ferrite ring?
Thank you very much for your help in advance!
Alex |
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lammert
Site Admin
Joined: 13 Mar 2007
Posts: 146
Location: Netherlands and Kazakhstan
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| Mar 12, 2009 11:53 pm |
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| You should first put an oscilloscope on the line and look what kind of communication problems you have. Ferrite coils only help to filter very high speed noise. Mains cable and loudspeakers are low frequency and ferrite won't help you much in that case. |
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olmari
Full Member
Joined: 02 Mar 2008
Posts: 38
Location: Vaasa, Finland
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| Mar 14, 2009 11:04 am |
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Also if nothing other helps, you can try to use shielded rs485 cable and ground the shielding properly so it does its job.
But as lammert said, it would help to know what type of interference there is, but ofcourse there isn't allways an oscilloscope on every corner.. |
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dreamweaver1408
New User
Joined: 10 Mar 2009
Posts: 2
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| Mar 14, 2009 11:05 pm |
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Hi!
I have got an oscilloscope and I have checked the data line. The problem is the data line is 100% OK most of the time but devices drop offline every few days to months in between. We have checked the cable/connections as far as possible and have replaced most of the hardware. Only thing left now is inductions through nearby AC cables and we also found some 477Mhz radio transceivers aerials nearby.
What type of choke coil could I use to suppress AC noise? |
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olmari
Full Member
Joined: 02 Mar 2008
Posts: 38
Location: Vaasa, Finland
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| Mar 14, 2009 11:08 pm |
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| If I may say, for that kind of interference an shielded cable would work better than any choke coil will, unless you can either move cables or wireless transceivers more apart from eachothers... |
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guest
Guest
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| Dec 26, 2009 5:02 pm |
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 would you like to inform regarding the circumstance or situation of the line when the errors occured?
for example)
- vibration like an earthquake
- humidity if raining
- lightning
- operation of a welding machine
- etc |
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