Yes, was measuring AC voltage. It’s probably a badly calibrated multimeter as all the AC voltage readings seem high.

I started with a wired Ethernet cable and 5V DC supply, and things worked well. Switching to wireless took a lot of time, but now I’ve got the wireless drivers working with good reliability.

The issue is that the system seems prone to brown-outs often when running from 24V AC with the USB wireless adapter. System works perfectly (wireless connects and passes traffic without lockups, regardless of CPU load) with a 5V 1000mA DC supply connected directly to the BBB in the same physical location. I’ve replicated this on the bench (short cables) and in the field.

I think I can have 120V AC available where this unit will eventually be installed, so I may just end up with two power supplies– a 24V AC brick for the valves and a 5V power supply connected to the BBB. Is there any problem powering the system with both a 5V brick (connected to BBB) and 24V AC simultaneously? I assume the 5V rail will draw from whatever supply has the higher voltage, but want to confirm that supplying 5V to the BBB will not harm the on-board AC-DC supply.