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Comment by Tepix | Hacker News Reader

Somewhat related: How unhealthy is it to wirelessly charge your phone (in flight mode) at night on your nightstand not far from your head? Have there been any studies?

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There hasn't been a lot of longterm research. Effects will also vary by frequency, intensity, etc. Some frequencies can cause heating, which is a problem for some areas like the eyes. Some frequencies increase glucose metabolism for the cells affected. No idea what that does longterm, but theoretically, that could create an environment for cancer growth.

The health risks of wireless phone charging are massively more psychological than physical. As they will very quickly abut claims of electromagnetic hypersensitivity, most of the legitimate research in this area focuses on the mental health of those who hold such beliefs against the overwhelming lack of any measurable physical phenomenon.

The concerns about the magnetic field may be bunk, but I had to give up using a wireless charger next to my bed because I could hear the coils making a ticking sound. Qi interleaves data with power so I assume the sound is the coils reacting mechanically whenever they interrupt the power to send a data packet instead.

I found that some USB wall chargers emit a high pitched whine when used to power a Qi charger as well, even if they are dead silent when charging a device directly.

Being able to hear the coil whine and finding it annoying is a fine reason to not like wireless charging. But I am pretty sure this is not what most people are going on about.

Is the ticking a function of a mechanical relay in a cheaper device, or the coil not being sufficiently glued down and moving as the magnetic field is turned off and on?

The sound comes from the windings within the copper coils vibrating due to Hall effect in the alternating magnetic field. Yes, the physical construction of the coil matters as to how much it would whine; tighter and more regular windings and appropriate potting/adhesives counteract the physical effects. The easiest mitigation, however, is to just use a switching frequency much higher than humans can hear. AFAIK the Qi standard supports the charger using anything from 80-300kHz and can vary depending on what the charger decides is optimum. Any audible coil whine from Qi would be attributable to harmonic mixing within the physical system of the vibrating coil. Also note that the coil whine could come from either the Tx or Rx coil, so you might easily eliminate it with a different charger that settles on a different frequency or has a better manufactured coil. But if the problem coil is the one in your phone, you might be hosed!

The latter I think, I found the volume varied depending on how the coils were aligned. I'll give it another shot once Qi2 brings Magsafe-like perfect alignment to non-Apple devices.

Claims of electromagnetic sensitivity have been debunked. They show symptoms to fake EM devices, and don’t show symptoms to real but hidden EM devices, so it’s all in their head. It’s the nocebo effect.

I charge wirelessly next to my head every night for the last 2 years (With wifi and bluetooth turned on) and sleep like a baby.

Now imagine doing this with an EV battery beneath you as it wirelessly charges from the ground.

Lots of interest groups would benefit from keeping any dangers of wireless frequencies under wraps.

Now if we start to ramp up to the sizes large enough to charge an EV battery, 1/r^2 isn’t going to be enough when you’re in the drivers seat

https://thehill.com/opinion/technology/4437988-why-did-nih-a...

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