On Fri, Jun 27, 2008 at 10:40 PM, Olin Lathrop wrote: > However let's keep in perspective the original question was what voltage > Dario should bus around his house to power a few distributed devices. > Simple buck regulators that are good enough can be easily designed with 12, > 24, or 48 volts input. I was advocating the higher voltage to reduce IIR > losses in the cable and maximize the amount of power that can be transmitted > for the same size cable. Over time he is likely to add more and more > devices, so designing now for more power capacity sounds like a good idea. > I envision a 48V off the shelf commercial power supply in the basement > powering the system all the time, then the modules bucking that to 5.6V with > a 5V LDO post regulator. We may disagree on whether 48V will be less > efficient to use than 24 or 12 volts, but in either case a few percent > difference in the modules isn't really the issue, and would probably be more > than offset by the cable losses anyway. If he uses off the shelf CAT5 > cable, then it will have a maximum current carrying capacity. At 48V that > same cable will be able to deliver twice the power to the distributed > collection of modules than at 24V. > In terms of distributed power, yes I agree 48V is better. But my original perspective is that 24V is more popular for automation (including home automation). Whether 48V is a safe voltage is a moot point as well. Typically we only consider <36V as safe. Xiaofan -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist