Wireless data transmission

For power, just mount a couple of permanent magnets on the stator and a coil on the rotor with a suitable rectifier/filter/regulator.

For data, optical will work if the environment isn't too dirty or oily. And if you can solve the interruption problem by mounting the TX/RX devices co axially. Practically any short range RF solution will work if its got some error detection/correction to overcome local noise sources.

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Paul Hovnanian  paul@hovnanian.com
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Have gnu, will travel.

ing

er

That's not a commutator unless it has sectors that make and break connection. It's 'slip rings' if it's just a connection to the rotating part. If you use two brushes onto a slip ring, probably the data and power transfer will be continuous (and a little ECC treatment can keep the data clean). Redundancy of brushes is... cheap. Three slip rings, power/ground/data, would that be enough?

Some transceiver technologies (18V CMOS, notably) can tolerate series- resistance changes better than others (RS-485 would be ... bad).

I would make a generator with the coils on the moving bit and the magnets on the fixed bit. The data could use a Bluetooth chip or an optical system.

Nice picture.

Web search for "slip ring". It can be made reliable. Your version of inexpensive may not expand to match most slip ring suppliers' version of inexpensive, though.

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www.wescottdesign.com

Ah, slip rings. That term escaped me, thanks.

Yes, 3 rings would be enough.

The power is frequency modulated with 116us period for 1 and 200us for

0 so it's between about 5 and 10kbaud.

MBQ

Every spinning VCR head assembly works this way, at 20-40MHz IIRC.

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Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

4Mbps Fast IrDA should do the data rate, and the chips and transceivers are off-the-shelf.

Theo

Thanks, that looks exactly like what I need.

rotating=20

are=20

copper=20

as=20

or=20

data=20

There lots of moderate to high cost ready made solutions out there. = Google=20 "Rotary coupler". They may give you some ideas, but watch out for = patents=20 owned by lawyers.

=20

Nonsense. You do not need a "carrier" at all. Direct modulation at 1 = MHz=20 will work when you have a decent S/N. It is often called Manchester = coding.