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Ldanielrosa

power vs. signal frequency

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Is there any serious problem with signal lines being close to power lines as long as the frequencies are the same and they are synchronized?

FWIW, I was thinking about using 15VAC (square wave, two phase, moderate frequency) to power some remote gadgets with a piece of telephone line.

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Actually, there are network devices that use your power lines of the house to communicate on. The AC is filtered out at the other end. Another example is the ABS brake system on most cars. The sensor sends an AC signal to let the processor know the wheel is moving and a DC signal is also generated to tell the processor that the sensor is functioning. This is so that the processor knows the wheel is locked and not a broken sensor wire when the car is moving and there is no AC signal. It is all a matter of filtering out what you do not want at the other end.

MP

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Hi there. This question actually is confusing me a little, are you saying the frequenciy in the signal line is the same as the frequency in the power line and are syncronized? Or do you mean that there is a DC power line and a signal line running close to each other?

//Staigen

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MP: I understand that filtering can remove a lot of interference. I'm hoping to make that unnecessary by aligning the bits (timewise) with the center of the flattened peak of the power (when the ringing is the least).

Staigen: Yes to the first question. At the moment this is conjecture. Since the devices would be remotely located, trying to supply 5VDC to all of them from a central supply is unrealistic. Since I may want to use some analog components, a split supply may be necessary. Raising the frequency allows for smaller capacitors.

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Yes, a schematic would be very helpful. I think that you are still going to have a problem with inductance characteristics. Filtering is going to be essential to make it work.
MP

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The advantage of AC power is that you can transmit at high voltage and low current, for low loss, and transform back to low voltage and high current at the load. But, 15 VAC is not high enough to be efficient, why not send the power as DC? The signal coming back could be on an AC carrier, or if it is logic could be sent directly with Manchester coding.

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Disclaimer: This is somewhere between conjecture and fantasy, so a schematic of my ideas is a bit difficult to produce.

That much taken care of...

russlk: I'm constrained by a few realities. The wire size is about 22ga, and I'd like to locate some gadgets 50m or more from the power supply. Some of them may have devices that want a higher voltage than 5V, or a split supply. If these are _ever_ subject to inspection, I want to keep _all_voltages low enough to be exempt from permits/regulations. I'd also like to load the power supply evenly regardless of the device in question.

all: The last point gets a bit sticky. To keep true with this objective, I may have to run uCs on a

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