In the main figure for HEGduino, it says that the low power of the sensor circuit protects tissue. While it is intuitive that an extremely high power EM field in close proximity would cause damage, I was wondering what backing there is for this statement specifically in relation to the device. Doing some searching on the subject, I found some relevant research, but it's a bit difficult for me to parse so I figured I'd ask and see if there was an easy answer.
Part of my concern comes from the fact I've been getting headaches after/during long (1-3hr) sessions using the device purely for recording, without attempting to control blood flow. Pain usually starts nearing the end of the first hour and continues for about 30-45mins after discontinuing use. It is possible that the discomfort comes from having the device strapped there and the hardness of the sensors/emitters, and I'll do a trial tomorrow to test that, but I find it unlikely.
Hey Ivan, First check none of the solder points are contacting your skin, it could be a 3V shock, which would build up heat slowly enough not to be noticeable for a period. Otherwise the wavelengths and power levels I'm using are safe and on par with other industry pulse oximeters (though mine isn't quite a pulse oximeter). The amount of power that actually penetrates your skin is very low anyway. The wireless stuff should not be a concern either, it's all toned down in power quite a bit and worst it can do is heat your skin on direct contact, though the ESP32 should not be on your skin if it's secured correctly. All things considered I've noticed this effect before after long term wearing without doing any training, and I wonder if it's a classical conditioning sort of reaction to seeing the flickering. You can see it plainly in the corner of your eyes if the sensor is close enough to them. Like maybe your brain is automatically stimulating blood flow in response to you sensing the flickering due to the association. This doesn't seem to happen to everyone mind you, but I would be curious what others' experiences are.