3 ms·
The paper seems to say they use 200 kHz sinusoidal waves for the field. If that translates directly into what I see in an FCC table of frequency allocations, th
by yourapostasy 9y ago
The paper seems to say they use 200 kHz sinusoidal waves for the field. If that translates directly into what I see in an FCC table of frequency allocations, then that is in the AERONAUTICAL RADIONAVIGATION regulated by FCC Rule Part Aviation (87) [1]. They are driving the signal at 6 Vpp (peak-to-peak), at most 0.42 mA current with the lowest-resistance spray. I don't know how to even crudely calculate radio interference from those specs, so would appreciate someone giving guidance on where to look for a start.
What worries me about this approach is the need for calibration. I don't see anywhere that indicates they've tested to see the effects of the wearing down of the topcoat and conductive spray layer upon the accuracy. It would be cool to be able to simplify a light switch installation to slap(electrodes)-spray-spray-calibrate, it would suck if I had to re-calibrate once every few years.
Now if we can figure out how to beam low-voltage, low-amperage power over building distances and through insulation, then we could remove a lot of copper runs. Beam just enough low power to drive and sense these kinds of control surfaces, and control relays sitting in front of the actual devices' electrical connections.
[1] https://transition.fcc.gov/oet/spectrum/table/fcctable.pdf https://transition.fcc.gov/oet/spectrum/table/fcctable.pdf
- joezydeco 9y agoThat's great detail, thanks for looking that up. The 200Khz wave may not be a big deal, but when you start getting strong harmonics then things really go south in your certification tests. Once on a capacitive screen controller design I had to stick in some pseudo-randomization on the electrode PWM to avoid this coupling. It was a pain in the ass.
- csoete 9y agoJust for your information (I am not big fan of the product), but there are battery free (energy harvested) switches which can replace copper runs already. See for example: https://www.enocean.com/en/enocean_modules_902mhz/ https://www.enocean.com/en/enocean_modules_902mhz/