Avoid conflicts with USB and external power supply

Using Arduino General Electronics
1

I have different designs that can be powered either by the USB port or via external 5v power supply, I want to avoid blowing up something and think I have soled it using two different strategies:

  1. By using two diodes

autopowerselector
autopowerselector1466×664 11.6 KB

  1. By using a mosfet

autopowerselector2
autopowerselector21131×484 8.55 KB

Both solutions seem to work and do it's job but ... which one is more reliable avoiding any possible problem if both the USB port and the external power supply are connected at the same time?

2

Either should work, the MOSFET solution uses less power then the 2-diode solution because the MOSFET does not have the voltage drop the diodes do. The MOSFET has one diode active when on USB and will supply a lower voltage to Vin. Both will supply the same voltage from USB.

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