1-Wire connection over powerline?

doofusNovember 8, 2012

I'd like to sprinkle my house with 1-Wire sensors (temperature - everywhere, humidity and flooding - in the basement), but the only wire already present in some locations is the power-socket (110V)...

Can the 1-wire microlan simply coexist with the AC power without short-circuiting and without the readings getting lost (that is, can I use the "white" AC wire as the 1-Wire data cable, for example)? If not, perhaps, HomeLink AV devices can be used as bridges?

Alternatively, maybe, the "interconnect" (red) wire of the Kidde-alarms (which we have literally everywhere) are usable for the purpose?

Thanks for any suggestions.

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yosemitebill

The term 1-Wire refers to the fact that the communications bus does not require two wires for separate clock and data lines such as in I2C. 1-Wire also supplies parasitic power over the same line to power several of the slave devices - but others still require local power.

You still must have TWO WIRES for it to work - one for data/power and one for ground return. The protocol does not allow for piggy-backing on other wiring. It operates on a voltage of 2.8-5VDC supplied by the master and requires it's own dedicated two wire network - typically twisted pair wiring is used.

    Bookmark   November 8, 2012 at 12:01PM
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brickeyee

While there are a few designs that use power line signalling, they almost always modulate a low power and frequency carrier onto the hot line and hope it gets to the desired location strong enough to be detected and used.

Some remote equipment is meant to hang across the power line for both power, a ground reference, and low rate RF signalling on the hot line.

    Bookmark   November 8, 2012 at 12:58PM
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doofus

You still must have TWO WIRES for it to work - one for data/power and one for ground return.

It was my understanding, the ground can be local in each location. That is, only one wire (carrying 'parasitic' power and data) needs to reach from slave to master (my computer). The second, ground, can run into the nearest grounding...

Here is a link that might be useful: Single-wire earth return

    Bookmark   November 8, 2012 at 11:34PM
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brickeyee

Using the earth at 120 V is not very effective (let alone signalling at even lower voltage).

While possible it is not generally done it works so badly

    Bookmark   November 9, 2012 at 12:36PM
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yosemitebill

1-Wire is a Micro-LAN - stress the word Network - that directly connects to data I/O pins of microprocessors, micro-controllers, and 1-Wire slave semiconductors.

The network loop operates on about 3-5 volts DC @ 1-5 milliamps through a pull-up resistor. The idle state is high and the connected devices sink current to produce the data pulses. The semiconductors use internal capacitors to store the parasitic power derived from the data line.

There is absolutely no way this can work on anything other than a totally dedicated low noise, two wire network. A third wire is also often used to carry the 5 volt supply to the slaves rather than utilizing parasitic power for improved reliability.

Here's a link to a very good 1-Wire design guide that you may wish to look at.

Here is a link that might be useful: 1-Wire Design Guide

    Bookmark   November 9, 2012 at 3:56PM
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