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I’m looking to create a battery powered sealed sensor device. Battery recharge would be via inductive coils. Is it possible to use the wireless power transfer as a data transfer link simultaneously?

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    \$\begingroup\$ Have you looked at any of the commercially-available inductive charging systems? Some of them include a data channel used for charging control, and may have design guides and/or patents that you may reference. \$\endgroup\$
    – nanofarad
    Commented Feb 10, 2021 at 18:46
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    \$\begingroup\$ The Qi standard used by many phones for wireless power transfer, specifies the use of modulating the power channel with data. \$\endgroup\$
    – Linkyyy
    Commented Feb 10, 2021 at 19:03
  • \$\begingroup\$ Yes it is possible. I don't know exactly how to do it but it is definitely possible. \$\endgroup\$
    – user57037
    Commented Feb 10, 2021 at 19:04
  • \$\begingroup\$ @Linkyyy The Qi standard looks like it has unidirectional comms from power receiver to transmitter. Do you know of any commercial systems with bidirectional communication? \$\endgroup\$
    – tomtomnz
    Commented Feb 11, 2021 at 1:04
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    \$\begingroup\$ @tomtomnz Sorry i dont have time to write a proper answer, but yes, all WPT systems has communication from rx to tx for the control loop. The receiver communicates with the transmitter by modulating the load, like turning transistors on/off with a digital signal, that loads the circuit down. \$\endgroup\$
    – Linkyyy
    Commented Feb 11, 2021 at 20:03

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Transmitting data from the charger is fairly easy, but signalling back from the load less so, although you might be able to do so by changing the effective load impedance between two states. Back in the 90s I worked on a system that used inductive charging and then had an infra-red link for data transfer, which worked very well.

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  • \$\begingroup\$ Thanks for the suggestion of infrared - good idea! Regarding the load impedance (excuse my lack of terminology) - are you suggesting that the changing load at the receiver would require change in power demand at the transmitter?creating a basic high/low state at the transmitter? \$\endgroup\$
    – tomtomnz
    Commented Feb 11, 2021 at 1:10
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    \$\begingroup\$ Yes pretty much. In a simple implementation you could monitor the current being drawn by the driver. The IR approach would mean that you could still transfer data when the battery was fully charged, which might be a challenge otherwise. \$\endgroup\$
    – Frog
    Commented Feb 11, 2021 at 8:58
  • \$\begingroup\$ Thanks @frog. One other rides I had was a second set of coils to transmit data using the device battery. So an input set for power + data in, a second set for data out. Would they interfere with each other? And would there be sufficient power from a battery? \$\endgroup\$
    – tomtomnz
    Commented Feb 12, 2021 at 19:37
  • \$\begingroup\$ That does beg the question of whether that arrangement would be any better than using a shared coil for power and data. I guess if the data channel is sufficiently out of band from the power channel then you should be fine. If you low pass filter the power at source and load then the data won’t be trying to drive into a very low impedance and you should be able to transfer data with the power on, off or modulated. \$\endgroup\$
    – Frog
    Commented Feb 13, 2021 at 0:10

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