Transferring data over induced coupling

[ardhuru]

I built a propeller clock (one of those POV things) a few years back, and am always looking for ways to improve the design.

My version uses a brushless fan motor, with a hand wound pair of coils to form an air-core transformer to transfer power to the rotating clock PCB.

The 'primary' is driven by a 555 oscillating at about 32 Khz; this I found to be somewhere near the optimal value. The pic on the PCB does everything, including driving the display, reading the RTC etc.

Now, I'd like to move the RTC to the base unit, to make the rotating PCB significantly lighter (the RTC chip, battery, holder). So, I need a way to transfer the time information to the rotating PCB; one way of course, would be to use IR.

But, I was wondering if I could inject this information into the transformer coil itself? Suppose I use another pic in the base to read the RTC, and then output the time serially, how could I incorporate that in the 32 KHz signal required by the transformer primary? Would it make sense to interrupt the modulation from the 555 to inject the time signal every few 100s of ms? I suspect the power transfer can tolerate this. My worry is, how well would the raw serial output travel over the induced coupling? And also, how easy would it be to filter out that signal from the rotating 'secondary'?

Yet another idea would be to get rid of the 555, and use the base pic itself to generate the 32 Khz, and periodically stop that to give out the time serially.

Do hope this doesnt sound too confusing.

Any suggestions, folks?

Regards,

Anand