Carrier current communication on Low voltage/high current AC

Tell me about it! BTDT, YMMV, ISTR, IIKTWIIN, etc, etc, etc....

Cheers! Rich

(and, of course, the big one: "I told you so!", which, as it turns out, isn't that great of a money maker. )-; )

On Fri, 10 Jun 2005 16:49:29 -0700, John Larkin wrote: ...

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Master!

Teach me?

Thanks, Rich

On Fri, 10 Jun 2005 16:49:29 -0700, John Larkin wrote: ...

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There are those who say, "The Customer is Always Right, Even When He's Wrong!"

Right or wrong, the Customer is the one who puts food on my table.

Of course, it would be nice if the customers would follow our advice such that they would continue to have money to put food on our table with.

Like the Psycho son of the Psycho PHB said recently, "Let him be proud."

Cheers! Rich

What, am I > >> A little one-off (at the moment) G-job here:

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How hard is it to separate a 9600 baud data stream from a 12VAC power line frequency?

Or is it too simple?

Thanks, Rich

Hello Mike,

Many PLC schemes simply blast RF onto the wires, with the driving impedance as low as can be. Or as low as the parts budget allows. A current coupling core would be way too expensive for most.

In Spehro's case this might work well if the driving transformer is high enough in RF impedance. Most likely it is. A few ohms can be enough. So in a low voltage app it would boil down to a stiff driver that is capacitively coupled to the lines and protected against spikes by diodes or something.

PLC such as X10 tend to fail when there is too much EMI filtering on the line, like all the X-caps and Y-caps. In LV gear that often isn't the case. IOW, know thy loads.

Regards, Joerg

the

ARGH! Is this an ego issue?

It should be trivial! You've got, what, 30M of 12V power line?

AC couple AFSK through a current transformer, and pick it off on a current transformer at the other end with a tone decoder.

Why is this turning into such an ordeal? Just because I joke around a lot people think I'm incompetent electronically? I _do_ know stuff, albeit at this point it's getting into an ego issue, and I have had a couple of lubricative imbibations, but still! C'mon! How hard does this have to be?

Thanks, Rich

But I suggested this very thing last Wednesday! Waaaaaaahhhhh!

)-; Rich

Ya gotta love it when that happens. I love that Gore Vidal quote - "It is not enough to succeed, others must fail"

Cheers Terry

Hello Spehro,

the

With respect to mains applications there is also a legal limit and most likely some further regs imposed by the utility.

Some that I had seen just pound logic level onto the line, via a stiff driver and a resonant circuit. The driver was often a plain old transistor because it cost a few cents less than a driver. On the line there may only be a volt or so left but that would be plenty if there aren't too many EMI measures inside the loads near the receiving end.

The trouble with X10 is that it's an AM protocol and if the level at the receiver drops below 100mV (which it easily does) reception becomes flaky. FM should be much more robust. Just make sure no harmonics will get you into regulatory trouble. That is another reason why a lower frequency can be an advantage. Personally I wouldn't go to 455kHz.

Regards, Joerg

But that wrecks all the fun! How about blow-in fiber?

John

Hello Mike,

LOL! That was a good one.

For X10, yes. For a good FM scheme you'd have lots of dB of head room but it depends on the noise that rides along.

Regards, Joerg

I like the wireless idea a lot more than carrier current. You can have a proper bandpass I.F. with plenty of gain to handle signal levels down in the microvolt region, and can go high enough in frequency to avoid most of the man-made noise. This is difficult to do at low frequencies with carrier current.

ISM is a good idea, but some bands are better than others. For example, Diathermy machines may wipe out lower bands, such as 13MHz, and induction heaters use other bands. These machines can have leads going between the machine and the load, so there is plenty of opportunity for radiation leakage.

The 2.45GHz band may be useless due to interference from microwave ovens. However, there is a way to use this band without interference.

Since the magnetron only produces power when the anode reaches 4KV, there is a brief interval at each zero crossing when no maggies anywhere are conducting.

Just use this to transmit and receive data, and you have the band to yourself:)

Mike Monett

Just plug an electric razor, vacuum cleaner or 3/8 inch drill in the same wall socket as the receiver and verify the system still operates. Even better, run them all at the same time:)

Mike Monett

Hello Fred,

Then there are the clients who think they don't need to spend the money on you, trying it on their own or offshore and never coming out with a product. I had a potential client do that until their financial backing ran out a few years later. In consequence the company no longer exists. Coulda, woulda, shoulda... the problem they had wouldn't have been all that difficult to solve.

Regards, Joerg

Hello Spehro,

Just food for thought: It may also be possible to use a shortwave ISM band in a common mode arrangement. 13.56MHz or something. Crystals are cheap and widely available. This makes the FCC issues a lot easier.

Sometimes when faced with similar situations I just use a function generator to pipe in a carrier and look how much comes out at the other locations.

Regards, Joerg

Well, if I have to mess with 2.x GHz, I'll just slap a Zigbee or two in there and be done with it.

Best regards, Spehro Pefhany

LOL! Sometimes it pays to post. Thanks - I was not aware this product existed.

Seems simple and attractive. Any reason you prefer to not use it?

Mike Monett

"John Larkin" a écrit dans le message de news: snipped-for-privacy@4ax.com...

Well, I once told a client that if he wanted the work to be done like this and like that, he had to go to the competitors. I also told them that they will fail like this and like that, which of course they didn't believe.

Guess who I saw coming back a year later?

Of course you have to be pretty sure of what you say.

A clip-on toroid looks real good... It appears that the real reason for most of the carrier communication stuff using differential Line-Neutral drive is the convenience of driving the signal out the same cord that powers the circuit- can't beat that. But someone is going to look none too bright installing all these filter components and line breaks when it sounds like all he needs is to pull a few bucks worth of cheap twisted pair through the power conduit- he can do this with a low voltage power circuit- but not a 120VAC type circuit.