I am designing a board with a uC to read data from a sensor and send to pc via USB.
I am using the 5V from USB to power the board and the sensor.
The board has 3 cables that are connected to the sensor: Data, 5V and GND.
My question is: I would like to protect the board against stupid users, in case someone decides to use an external power supply.
I would like to know if there is a simple solution for that, like a diode. The problem with this is the voltage drop, which is too big for the sensor, since the USB voltage is not always perfect 5V.
Is there something I am missing here? Or should I aim for something a little bit more complex, like amp-op?.
Is there anyone out there that has done something similar?
Any tip will be appreciated.
Thank you very much!