(Replying to PARENT post)

Could you put a pressure sensor on the pad and only power on the coils directly underneath the object? I assume with software you could selectively turn on/off areas of the mat to manage the heat problems that come with multiple coils being on at once. I could see it being a problem if they were charging all at the same time but you should be able to fake it and call that good enough. All the devices have to charge, but they don't have to all charge at once. I think you could get tunnel vision and forget that.

Could someone who is better qualified tell me why that wouldn't work?

👤pg_bot🕑6y🔼0🗨️0

(Replying to PARENT post)

There wouldn't be any need for pressure sensors; this already happens. The charged device adds some power to its own coil and the charging station detects that (it's unidirectional communication). For example my charging station lights up about a second after putting my phone down, and can show the battery status with the light. I would assume that when there's nothing on them the coils transmit in a low-power mode, with the protocol allowing the device to ask for more/less power as required (edit: Wikipedia confirms that the device can actually send some pretty precise instructions to the station, with voltage controllable in 50 mV increments [0]).

So logically it would seem the heat issue happens when there are three coils active at the same time transmitting at high power - the peak heat output is the issue.

[0]: https://en.wikipedia.org/wiki/Qi_(standard)

👤the_pwner224🕑6y🔼0🗨️0

(Replying to PARENT post)

Right. Or similarly, you could figure out which coil(s) were drawing the most power and perhaps power the others down?
👤leoh🕑6y🔼0🗨️0