switching power sources I have a small project I am working on that accepts power from either a 5v DC power source or a USB power source.
Now, I know that both of the power sources are effectively 5v. I have measured the power on both with my meter and can see that the USB supply is at 5.4 and the DC supply is at 5.01v.
I would like to be able to build something that switches over to the USB supply when the cable is connected. However, I have never done this before. I have taken a look around on Google already and have read some things about P Channel MosFETs and PowerPath controllers - but I am a little confused as to whether the two incoming voltages I have are suitable for this?
Would someone be able to give me a little advice on this at all?
Cheers,
Rafa
Consider copying the Arduino Uno reference design.  This is part of that schematic showing the MOSFET used to turn on / off the USB power when the barrel jack power source is active: