Signalling over power line

Hello all, I'm looking for a method to send digital, very low bitrate over power line. The signalling must be bidirectional, at a baud rate of less than one bit per second (can be half duplex). The power line carries 220V RMS at a current of about 10A. The distance between the two stations is about 10 meters. All the vendors I found produce such chips for broadband communication, and this is an overkill for my application.

Thanks, Avishay

Reply to
avishay
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"avishay" ha scritto nel messaggio news: snipped-for-privacy@g49g2000cwa.googlegroups.com...

Hi think you can take a read on X-10 protocol, this one is used in home application to send digital signal through the power line.

If aI can remember right Marmitek have some power modem, then a modem wich through a serial cable conected to the PC is able to inject our signal into the power line. At the other end simply put another power modem to retrieve the data signal.

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Hope this may be useful for you.

Bye Fabio

Reply to
POWERMOS

"avishay" ha scritto nel messaggio news: snipped-for-privacy@g49g2000cwa.googlegroups.com...

Some other useful link:

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Cheers Fabio

Reply to
POWERMOS

You're looking for X-10. A very old but widely used home automation protocol. It transmits data during the powerline's zero crossing so you'll get roughly 100bps (two zero crossings for each half of a 50Hz waveform, if your powerline is 60Hz then you'll get 120bps).

Reply to
slebetman

Thank you all, but the X-10 way is still way beyond the requirements. It is also too bulky for the space I have (it should fit inside an existing box) and too expensive. I thought of using a small current sense transformer, designed for the

20KHz-50KHz range, modulating the signal using FSK. On the receiving side, I want to put another transformer of that kind, bandpassing its received signal and detecting the FSK signal. Does anyone have an idea if such setup might work?

Thanks, Avishay

Reply to
avishay

Blah, Blah, Blah .............................................................^ UNSTATED requirements - if you do did not care enough about them to specify any in an operative format then why do you think anyone will care enough to even begin solve your "problem".

Jeez: You can send exactly one bit with by shorting the supply with your tongue, if that is lowly & cheaply enough for you!!

Why do you think that implementing a power line modem yourself will be smaller, cheaper, simpler and smaller than the chipsets already designed for exactly that purpose, tested over the years and available in volume right now??

Especially when you cannot say what you want.

Reply to
Frithiof Andreas Jensen

"avishay" schreef in bericht news: snipped-for-privacy@f14g2000cwb.googlegroups.com...

Something like that can be done. But since the impedance of the mains is pretty low, you may have to provide quite some energy by the transmitter to reach the receiver. Or you have to place filters on both sides. Power companies sometimes use a signalling protocol that shorts the mains a (very) short time before zero crossing. But... as you apparently have no experience in this field, I guess the cost of learning will rise way beyond the use of readily available solutions.

petrus bitbyter

Reply to
petrus bitbyter

That is basically how X.10 works. It superimposes a high frequency signal on the power line at 0, 60, and 120 degrees. They use 120kHz rather than

20-50kHz. Their coding strategy is to use a kind of manchester coding, in which a binary 1 is encoded as a 120kHz blast at zero crossing (and at 60 and 120 degrees) followed by the absence of a pulse for the next 1/2 cycle. A 0 is encoded as no pulse followed by pulses. The pulses are defined as 1ms of blast.

A communications protocol is built on top of this simple scheme using various combinations of dead cycles, 0, and 1 bits. You'll have to come up with your own scheme anyway, so why not use something that you know will work? Also, if you implement the same scheme, you can use off the shelf controllers if you want to extend the system.

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  Bob Monsen
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Reply to
Bob Monsen

Something a bit like that worked excellently during WW2, with signal sent quietly in the background of speech radio transmissions.

A filter is fairly essential, L on the mains to stop it shorting out your rf, and C on the rf kit to stop it getting fried.

While you can use standard protocols, simple digital circuitry to produce 2 frequencies may be all you need for some apps. Depends how you want to handle transmission data errors.

For some types of data, errors dont even matter, eg where baud rate is well in excess of data bandwidth. These would be most simple to design for.

If you dont need isolation you could skip the transformers.

NT

Reply to
meow2222

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