I guess this is not the right forum

[rrb011270]

Mabuhay!

I have a project that will use the RS485 thing... I have the system running with a few protocols implemented... but I decided if it is possible to have my power supply distributed to a network using bus..

I used a 6-wire bus cable and I have three vacant... I would use this to transmit my dc power to the different slave devices...

Anybody in the community can provide info, site and/or schematics as a startup..

Thnx

[MikeW]

I have used RS485 extensively.

I used RJ45 plugs,sockets and cable.

Its widely available, since it is Ethernet hardware.

I use all 8 wires,

1 common
2 +9volts
3 Data +
4 Data -
5 Data -
6 Data +
7 +9volts
8 common

that way, it doesnt matter which way you crimp the plug to the cable, also you have redundancy should one pin go faulty

the +9volts gets regulated down to +5 as necessary on each module
I current limit the +9volt power supply with a resettable polyfuse.


dont forget TVS diodes for transient protection on the data lines

you can get 4 in a SOT23-6 package

Hope this helps.

[Guest]

If ok can u provide the schematics in applying your setup...
I want to see the complete picture on how u place the TVS at the data lines.

Thnx

[rrb011270]

Mabuhay!

Would it be possibel if u can share the schematics of power supply circuits? What's this TVS thing?

Which do u think is more reliable the DC or AC implementation?

[Guest]

Hi there!

I am currently doing somthing very similar with RS485 data and power on the same cable.

I am still in the early stages of developement (not hardware as yet) but this is what I have done.

I am using RJ45 connectors, with standard Cat5 networking cables so it is very cheap and easy to maintain. I am using the same connections as described on the website :-

http://www.aptcommunications.com/ncode.htm

(there are plenty of others aswell, a searchs along the lines of Cat5, connections, diagrams etc should show loads).

Rx+ and Rx- must be on a twisted pair, as must be Tx+ and Tx-, to stop EMI and EMC problems.

I am then using pins 4 and 7 to supply 5V, with pins 5 and 8 supplying the 0V referance. There is a new Power Over Ethernet (PoE) standard, which specifies different connections to this (which I am currently looking into, but I dont seem to be able to find much data on it - any ideas, anyone ).


As for how to get the power into the system, I am not quite that far on yet, but I suspect a box with DC in, RS485(no power) in and RS485(with power) out will be how I do it, the DC simply being connected to the appropriate pin of the connector.



Hope this is of some use

Richard

[SherpaDoug]

A lot of scientific instruments use 12VDC and RS485 on a 4 pin connector like this:

pin 1 Ground
pin 2 Data +
pin 3 +12VDC
pin 4 Data -

Be sure if you are using RS485 (one bidirectional data pair) or RS422 (one data pair each way).

I read one article about a Power Over Ethernet protocol and it was very complex with power level interrogation and negotiation. It was far too complex for anything I build until someone makes a dedicated power control processor for it.
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