I've bought a AC/DC adapter which per its specifications should output 5VDC and deliver 3A. I was going to use this adapter to power my BeagleBone Black (BBB) with. However, when I'm measuring the output from the adapter while it's idle (not powering anything) with a good-quality multimeter, it reads 5.24V.
The BBB System Reference Manual (Rev. C) states the following:
The board requires a regulated 5VDC +/-.25V supply at 1A. A higher current rating may be needed if capes are plugged into the expansion headers. Using a higher current power supply will not damage the board.
As one can see, my adapter outputs a voltage that's pretty close to the upper limit of 5.25V that the manual says is the maximum supplied voltage for the BBB. Is it still safe to use it to power my BBB with?
U/R*I -> I = U/R = 5/10 = 0.5A
Nonetheless, I hooked it up and measured the voltage to be 5.03V, so given that my calculations aren't too far from reality and that my test was 'OK', you were right about the voltage to drop. But what if the BBB would be connected to the adapter and fed with 5.23V while not being powered on - could that damage it? \$\endgroup\$ – InquisitiveMonkey Sep 12 '14 at 3:21