| ??? 09/13/06 15:23 Read: times |
#124209 - the worse 485 wiring Responding to: ???'s previous message |
Erik Malund said:
I even have seen "wiring RS485 in a star configuration" OUCH!!. Despite of how many notes we wrote on RS485 wiring and in how big and bold letters it is written there "NO STAR", and "NO ETHERNET WIRING", the typical installation situation is, "we had a company who pre-wired the premise for us" and granted there sits the structured ethernet cabling, under the plaster on the wall or whatever so we can't simply change it. Erik Malund said:
A typical idiocy (this from the wikipedia) "Ideally, the two ends of the cable will have a termination resistor" Huh, how true! Again, no matter how much paper and ink (sorry toner) is spent on this and how many times I and my colleagues repeat to those who install and service that the terminator is a must (it's just putting in the jumper), invariably there are two states: either a jumper is present on each node, or nowhere, depending on how the assembly house set it... So, we run max. 19200, standard load, all the protection available, and very very defensive protocol and coding. Most of the time, it works satisfactory. Now, this belongs to the "worst 485 cabling and practice" thread and not this one, I know... Jan Waclawek PS: Erik, please don't argue, please do accept that I simply have no influence on the idi... sorry personnel who actually install this, except I put it into the documentation to back my..self. |
| Topic | Author | Date |
| RS485 and DE, \RE | 01/01/70 00:00 | |
| not pantyhose | 01/01/70 00:00 | |
| Thanks Erik | 01/01/70 00:00 | |
| stick to the National and B&B stuff | 01/01/70 00:00 | |
| the worse 485 wiring | 01/01/70 00:00 | |
| automatic termination is the solution | 01/01/70 00:00 | |
| what\'s that? | 01/01/70 00:00 | |
| its simple | 01/01/70 00:00 | |
| Cool! | 01/01/70 00:00 | |
| hmmm | 01/01/70 00:00 | |
| actually very simple | 01/01/70 00:00 | |
| I am still none the wiser | 01/01/70 00:00 | |
| chain | 01/01/70 00:00 | |
| I've got it. | 01/01/70 00:00 | |
| It works, you work out the details | 01/01/70 00:00 | |
| maybe not biasing A&B... | 01/01/70 00:00 | |
| then use a high enough voltage | 01/01/70 00:00 | |
| biassing | 01/01/70 00:00 | |
answers | 01/01/70 00:00 | |
| if you supply via cable... | 01/01/70 00:00 | |
| Transceiver with switchable termination | 01/01/70 00:00 | |
| thanks for the tip! | 01/01/70 00:00 | |
| great.Oliver, just this | 01/01/70 00:00 | |
| it would, but think this through | 01/01/70 00:00 |