Protecting RS-485 busses

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jgmdesign
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Posted by jgmdesign: Mon. Sep 23, 2019 - 01:52 PM
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Interesting short read:

 

https://www.digikey.com/en/artic...

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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kabasan
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Posted by kabasan: Mon. Sep 23, 2019 - 04:25 PM
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This is the circuit that I use a lot for my product.
Please use as a topic in this thread.

 

In order to omit expensive high wattage resistors, low wattage resistors are used in parallel.

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jgmdesign
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Posted by jgmdesign: Mon. Sep 23, 2019 - 04:46 PM
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kabasan wrote:
In order to omit expensive high wattage resistors, low wattage resistors are used in parallel.

 

Ok, I'll byte.   How is this cheaper?   a 1 watt 120 ohm resistor is maybe $0.22usd?

 

https://www.digikey.com/product-...

 

5 1/4 watt resistors are $0.10 each:

 

https://www.digikey.com/product-...

 

PLUS then there is the PCB layout/fab costs.

 

so how is 5 resistors cheaper to use than one ?

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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kabasan
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Posted by kabasan: Mon. Sep 23, 2019 - 04:55 PM
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The examples are just in line with my special environment.
In my case there is only a small amount of production, so I don't want to pay for the purchase, maintenance and management of the 120Ω that I use only.

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Bronze Markawneil
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Posted by awneil: Mon. Sep 23, 2019 - 05:28 PM (Reply to #4)
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OK - but that wasn't what you said in your first post!

Top Tips:

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kabasan
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Posted by kabasan: Mon. Sep 23, 2019 - 06:08 PM
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Expensive I say is not determined only by the unit price.
Sorry at the lack of explanation.
Should we write high cost?

Last Edited: Mon. Sep 23, 2019 - 06:09 PM
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jgmdesign
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Posted by jgmdesign: Mon. Sep 23, 2019 - 06:21 PM
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I think the subject other than the OP should be dropped before the fights start.

 

JMO

 

JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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m.majid
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Posted by m.majid: Mon. Sep 23, 2019 - 07:33 PM
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AN-1057 worthes to remind again, is mentioned several times before in this forum.

. 

There are also robust RS-485 ICs that can survive from wiring faults and ESD of harsh environments.
.
IC manufacturers use keywords such as:
"fault protected"
"fault free"
"fault tolerant" 
 

Majid

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