Carrier current communication on Low voltage/high current AC

No, the customer is not always right, but he's always the customer.

It's perhaps an appropriate application for the technology (low power, low speed signalling/data transmission), but the toolchain and so on is pretty involved for a one-off. Here's the RF section- as you can see, it's dead simple. All the RF smarts are in the IC design (the small one at the top, of course, the larger QFP is a micro).

Best regards, Spehro Pefhany

Except when you decide to fire him.

Best regards, Spehro Pefhany

Yeah. Sometimes the culture is such an obvious mismatch that you just have to walk away, even when the deal would be mutually beneficial. My biggest problem is usually with high-level people, often PhDs, who just *have* to be smarter than anybody else. Physicists are probably the worst.

John

It seems ideal for many of the projects I get involved in. Thanks!

Mike Monett

Things may seem quiet for a long time, then a new company can move in next door and everything goes to hell. It reminds me of a consulting trip to LA back in the 1980's. I happened to look out the window during a break and noticed some people dressed in funny suits wandering around my rental car making measurements.

I asked my hosts what was going on, and they said the company next door was working on some kind of linear accelerator for military applications, and I happened to park in the beam. They were checking to see if the car had become radioactive. That was 20 years ago. I guess they could melt the car with today's technology:)

Mike Monett

Don't throw out the baby with the bath water, some of them may really have something to say. But most of them talk because they have to say something, of course.

I like the idea someone mentioned, to simply send bits from the cpu to the mains, with a capacitor as the connection to the mains.

In a 3-phase house short the phases, for the signal frequency, with two

Prepare the message in the memory, and then write it out to the output port in a steady stream, frequency 100-455kHz. A simple output stage gives some oompa to the signal before sent into the mains wiring.

The receiver circuits. Selectivity through LC circuits, or 455 kHz filters, and amplification, like a simple IF stage in a radio. After that we have the cpu, which runs at a much higher frequency than the signal frequency, so we can use the cpu to analyse the received signals. Use error-correcting code.

Every unit has a number, and adds this number to every message it sends.

A central unit takes control of the system and polls the units.

All units need a cpu, and selectivity receiver circuits, and the power output stage for transmitting. A high voltage capacitor and maybe other safety components for the connection to the mains.

To receive the bits we could use a flank sensitive circuit instead of resonance circuits for selectivity. The flank sensitive circuit reacts only to flanks within a certain risetime range.

Hello Fred,

Yes, good point. It's just that much of this wireless gear is very limited in range. It takes a simple obstruction and reception is gone. Next to our lab there is a wall which contains aluminum backed fiber insulation. I can't even walk behind there with the cordless phone without losing the call.

I am afraid ZigBee could be affected as well. If Spehro's solution was for, say, irrigation equipment and someone places frost cover blankets over it in the fall this could already block the RF path. Sometimes PLC is just the ticket.

Regards, Joerg

Hello Mike,

Yes, although I found that if you aren't in a heavy industry area and away from hospitals even 13.56MHz is pretty clean. Out here (east of the Sacramento burbs) that frequency is open.

That's a good idea. But then there are WLAN, cordless phones and so on.

Regards, Joerg

Then you have no customer. ;-)

Everyone has a customer, even "captives" like myself. I can also fire my customer, and he me. Until either happens, he *is* the customer though. ...after I'm a free man. ;-)

...and they let it loose? Yikes! I guess it's a good thing you weren't living near a medical research facility.

Yeah, Zigbee is nice! Just finished a project using the Freescale chips, and it was pretty simple. Freescale is coming out with a chip that combines their Zigbee radio and the HC processor in a single package that will really lower chipcount. The big problem is getting all the protocol stacks set up...

Charlie

I think they are ideal for some applications. Inexpensive, simple, small, low power, good data rate, reasonable range, different LAN modes, large address range, security, multiple vendors... what did I miss?

Thnx, Speff.

Mike Monett