I currently produce a product which uses a 9v battery with 5v regulator like an Uno, I use bluetooth with this to send data to PC. I want to produce a version based on Nano that uses USB port for both data and Power.
Problem is the sensor is powered by 5v and its output is obviously dependant on the 5v. I use the internal 1.1v reference. The unit is calibrated for the specific sensor at assembly time.
My question is regarding USB power. I am concerned that the USB power on different computers may vary considerably as the spec is 4.5 to 5.45v I think. Does anyone have experience with this? If my calibration is done on my pc at 5.02v and the users pc only gives 4.8v, the result will be incorrect.
Maybe the USB power should be limited to 4.5v ? Could not use a regulator here, maybe just a zener?
Any advice would be appreciated.