is that I need an optocoupler with a programmed distance of 1000 meters with CAN bus

[picdad]

is I need an optocoupler with a programmed distance of 1000 meters with CAN bus

hi ,
I found it on the CAN bus but I want SOMEBODY explain this to me. "For a length of bus, CAN, greater than 200 meters it is necessary to use an opto-coupler, and a length greater than 1 km bus it is necessary to use interconnection systems such as repeaters or bridges "


if I scheduled my bus with 50 kbit / s, ie a distance of 1 km I will not need either an optocoupler or a system interconnexionat
?
is it true?

 

[chuckey]

As your bus cables get longer they pick up more interference and the two ends start getting spurious voltages induced in them. The equipment at either end will also be grounded to separate earths. If you use opto isolators, you can isolate the cable from these effects.
When the cables get sufficiently long the waveform gets distorted (sloping edges), so they need to be regenerated.
This sort of thing is highly dependent on the quality of the cables and the local installation. One thing not to be ignored with very long data cables is lightning protection. If one site has a nearby lightning strike, its local earth potential will rise to as much as 20 KV above the actual earth. If this earth is connected to a different one that is still at 0V, then huge currents can flow down the data cable and cause much damage at the FAR end.
Frank

 

[picdad]

thank you for reply, I have another question, can I use the wire CAN_V+ to power the cards that are connected to the CAN network, or it is necessary to supply each card a external power ?