Sascha, that's correct, once the 5V rail is loaded the 12V rail is properly (properly depending on the power supply quality) regulated. Apparently, switched power supplies need a proper load to correctly regulate voltage. You may try something like 1A in the 5V rail. Be sure to use a resistor which can tolerate 5W (4,7ohm, 9W for example) !
Ismael 2010/5/13 Sascha Silbe <sascha-ml-ui-sugar-olpc-de...@silbe.org> > 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)? > > > > CU Sascha > > -- > http://sascha.silbe.org/ > http://www.infra-silbe.de/ > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.10 (GNU/Linux) > > iQEcBAEBCgAGBQJL7ApLAAoJELpz82VMF3DacX4H+wdaJccvnIKGh8+7CvdAeQnQ > FuhShcjiM3h6MzZTPxLXH4KjDm8upzGCtPJlNLGl9izL+MPizGdebiufMRujeouH > ZZk3Da/RhtIsugKPKYLVBuXo2bGX6vG4Jsm4VExRHWxQjS8WBV6UTW2iYMOkOjt4 > Awb78u/K9A/WoS6L2Az/ZTRvs1VHiprdWoMtGtLJA13FJ5LZaixuTmWk14ZCAMRK > NdGM3sD36PJzUlHejDDJADxWeLhLnkbbLDaf+AbS3rQYGpTbNnVEh80yiWRKYTkp > JYc5YMAjsXyKelMmVJaiQRfea2juJ3rUALn/rq1F4xL74rVSm273D5dxVS3tbbU= > =QlEW > -----END PGP SIGNATURE----- > > _______________________________________________ > Devel mailing list > Devel@lists.laptop.org > http://lists.laptop.org/listinfo/devel > > -- Ismael Schinca Plan Ceibal - Depto. Técnico - I+D Avda. Italia 6201 Montevideo - Uruguay. Tel.: 601 57 73 Int. 2227 E-mail : ischi...@plan.ceibal.edu.uy
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