On May 13, 2010, at 10:18 AM, Sascha Silbe wrote: > On Thu, May 13, 2010 at 09:24:17AM -0400, John Watlington wrote: > >>> FWIW, I've also used a ATX power supply to power an XO-1, but stopped doing >>> so once I discovered why the XO-1.5 would run from it: Being a cheap model, >>> it regulated only the 5V rail, so the 12V rail dropped down to 9V with a >>> switched-on XO-1 connected to it. The XO-1 barely coped (the power light >>> started flickering some time ago, probably due to the power supply aging >>> and delivering an even lower voltage than before) and the XO-1.5 (without >>> MPPT ECO) didn't like it at all (whining noise, LED off). >>> >>> Summary: If you're trying to replicate this setup, make sure your PC power >>> supply regulates the 12V rail (just hook up some load and check the >>> voltage). > >> Many higher power supplies like AT/ATX power supplies don't >> work properly when unloaded. I bet if you draw a couple of >> amps from the +5V supply, you would find that the +12V supply >> starts working fine. > In what way is that different from what I wrote? Or are you saying that once > I draw a certain amount of current from the 5V rail, the 12V one will be > properly regulated (i.e. keeping the voltage stable at 12V +/- 10% regardless > of the current draw on the 12V rail)?
Your latter statement is correct. There is usually a "main rail" (+5V or +3.3V) which must be loaded for the "auxiliary rails" (+12V) to be regulated. Cheers, wad _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel