Two wires bus for data and power

There are many commercial solutions for home-automation systems that are based on a two wires bus both for bidirectional data and for powering the modules. The number of connected modules could be high, 100 or more.

What is the technology of those kind of buses? Are they simple half-duplex RS485? In this case, how the power can be distributed on the same wires of data? Is the protocol master/slave? In this case, the time to poll all the modules could be some seconds and the reaction of user commands is very bad.

Or are there other solutions?

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pozz
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luni, 18 aprilie 2016, 13:12:49 UTC+3, pozz a scris:

24VDC is the minimum I'm aware of. There are also solutions for 220VAC. You need quite expensive specialized driver chips. These are like RF chips: they modulate some frequencies on the carier wire like the RF parts do over the air. For details search the web, but this is the basic technology.
Reply to
raimond.dragomir

There are a few. HART, Foundation Fieldbus H1, Profibus MBP, etc.

No. Typically you AC-couple manchester-encoded (or FSK) data onto the wire-pair. You also have to add a filter to your power-supply to make it high-impedance at the comm frequencies.

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Grant Edwards               grant.b.edwards        Yow! Now that I have my 
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Grant Edwards

I did a two part blog on some of the options

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I hope this helps a bit

-Aubrey

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Reply to
antedeluvian

The general idea is that you use diplexers everywhere, to separately couple DC and comms onto the same set of wires.

But -- there's a reason that wireless is popular.

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Tim Wescott 
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Tim Wescott

A proprietary system that I once worked with used a DC voltage for logic high and a somewhat lower DC voltage for logic low.

Peter

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Pete

Il 18/04/2016 14:49, snipped-for-privacy@gmail.com ha scritto:

Quite expensive? They are products for consumers. It isn't a low-end market, but it isn't industrial too.

It's very simple to have 50-100 modules on the bus even for small-medium private buildings (homes).

I couldn't find any ready-to-use chips, except KNX standards that are very closed and it seems impossible to understand the technical details of the bus.

Reply to
pozz

They seem all industrial solutions where the cost is higher than consumer market.

HART seems a master/slave protocol, it can't be used for building automation applications, where you need a fast response to a push button press.

Are there any ready-to-use cheap solutions? I don't think building automation products are based on complex and big electronic boards.

Reply to
pozz

In this case, each module on the bus should be capable to inject a DC voltage on the bus (and changes its value when transmitting). I don't think it is a simple solution.

Do you remember the bitrate?

Reply to
pozz

Any ready-to-use chips or reference designs to suggest?

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pozz

mar?i, 19 aprilie 2016, 11:47:00 UTC+3, pozz a scris:

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ST7540 ST7538 ST7570 ST7580 ST7590 Mouser have them all

Reply to
raimond.dragomir

Nobody said anything about the consumer market.

Mostly, but not entirely

And now we're talking about building automation?

Perhaps it would have helped if we knew you looking for cheap, consumer-market, building automation technology. Are you?

Are you looking for mains powerline communication?

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Grant Edwards

Home automation is consumer market.

Yes, my original post was about "home automation".

I'm curious about commercial (already on the market) technologies that allow to create a bus with only two-wires for power and data.

I'm interested mainly in consumer medium/low price products.

Is powerline used only with AC mains (230/110Vac)? Home automation systems usually have small devices that are DC powered.

Reply to
pozz

Il 18/04/2016 12:12, pozz ha scritto:

One technology already used in home automation systems is KNX on twisted pair, what is called KNX TP1-256.

You have a two-wires bus where DC voltage (about 30Vdc) and data (9600bps) are mixed together.

On a KNX bus line you must have a specific KNX bus power supply that injects DC voltage for powering modules on the bus.

When one node wants to transmit zero, it puts a load on the bus for

35us. The load should sink as much current as possible to have a decrease of 6-9V on the DC voltage on the bus.

The power supply integrates a choke that should make the magic.

There are some ready-to-use chips that integrates many useful features: bus coupling, DC/DC, bit decoding and so on. For example, ON semiconductors makes: NCN5110, NCN5121 and NCN5130.

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pozz

Il 19/04/2016 11:05, snipped-for-privacy@gmail.com ha scritto: > [...]

Those chips are for powerline (mains AC). Could they be used with DC low voltage (12-24V) too?

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pozz

Il 18/04/2016 12:12, pozz ha scritto:

Another simple solution, IMHO for very specific situations:

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pozz

Il 20/04/2016 09:48, pozz ha scritto:

There is an application note from ST that shows how to use their PLC modem in DC powered bus applications.

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Other manufacturers make PLC modems that should work in DC bus. For example ON Semiconductor (NCN49599), NXP (TDA5051A, up to 1200bps), Cypress (CY8CPLC10), TI

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There is an israelian company that sells a proprietary solutions:

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Did someone use one of those solution? Any suggestions for a low-cost consumer applications? What I need is to have a DC powered (10-30Vdc) half-duplex multi-master proprietary bus with a low bit-rate (at least 9600bps). The number of nodes will be 50-100 at maximum.

Reply to
pozz

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