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What is maximum cable length between iButton and PIC?

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1-Wire cable length

Hi. I am doing some project with iButton and PIC. I would like to ask you what is maximum cable length between iButton and PIC and which type of cable should I use. I am a little afraid of EMI because a long cables should be connected directly to several pins of PIC. What is yours experiences?
 

Re: 1-Wire cable length

Hello,

I think, unshielded twisted pair should be o.k. for most applications. E. g. Conica-Minolta uses it inside photocopier/printer to access toner id-chips, could be 1 m cable length for each chip, several connected in parallel at controller board.

I remember, the topic is also widely discussed in some Dallas application notes.

Regards,
Frank
 

Re: 1-Wire cable length

FvM said:
Hello,

I think, unshielded twisted pair should be o.k. for most applications. E. g. Conica-Minolta uses it inside photocopier/printer to access toner id-chips, could be 1 m cable length for each chip, several connected in parallel at controller board.

I remember, the topic is also widely discussed in some Dallas application notes.

Regards,
Frank
Click to expand...

Cable length that my application required is approximately 15m in noisy enviroment (mostly fluo lamps). Can you point me to that application note. I skimed through some today and didn't find anything useful.
 

Re: 1-Wire cable length

Hello,

in AN244 "Advanced 1-Wire Network Driver" cable length up to 100 m is discussed. Noise immunity of 1-Wire-Protocol is said to be based on integrity checking and retranmission when necessary, see app159 "Ultra-Reliable 1-Wire Communication". To my opinion, If the fluorescent lamps aren't switched on and off permanently, you have a good chance of succesful transmission after one or two retries at maximum.

Regards,
Frank
 

Re: 1-Wire cable length

FvM said:
Hello,

in AN244 "Advanced 1-Wire Network Driver" cable length up to 100 m is discussed. Noise immunity of 1-Wire-Protocol is said to be based on integrity checking and retranmission when necessary, see app159 "Ultra-Reliable 1-Wire Communication". To my opinion, If the fluorescent lamps aren't switched on and off permanently, you have a good chance of succesful transmission after one or two retries at maximum.

Regards,
Frank
Click to expand...

I am reading iButton often is possible and I'm doing crc check. Thats not a problem. I am consider of eventual strange behaviour of PIC (reset, buging...)
 

Re: 1-Wire cable length

Hello,

yes, the PIC interface should be mainly protected against voltage transients, that could probably damage it. Also high frequency interferences should be supressed. I think, that the "Advanced 1-Wire Network Driver" circuit is a good starting point. To suppress interferences, a common mode filter could be meaningful.

Regards,
Frank
 

1-Wire cable length

hello,
max 10m for ds18b20
 

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