Post by thread:[EE]: rationalising power supplies

The closet has become the communication closet (much to my wifes annoyance) and contains or provides power for via PoE the following server, printer, scanner, amplifier, tuner, 2 x 5 volt VOIP adapters, 2 x 12volt wifi routers, 3 x 9volt cordless phones, 4 x 12volt usb drives, 1 x 9-25 volt pic-maxi-web, 1 x 24 volt ac water solenoid PSU. 1 x 5 volt IP camera A total of 14 wall wart style PSU's many of which terminate on DDF krone strips so I can easily do my own version of PoE. This keeps the end units tidy as there is no ugly PSU to be seen. Under test the so called/labeled 9 volt psu's for the cordless phones still provide 11.45volts at the base unit when loaded and drop down to 10.45Volts when charging the remote unit. Unloaded they measure 12.3volts. So I suspect they will tolerate a 12 volt regulated supply. So I am entertaining the idea of using 1 ex PC PSU that provides 12v 8Amp and 5v 20amp. Therefore all the 9Volt and 12 volt devices will be supplied by the 12volt rail and the 5 volt devices from the 5 volt rail. This would reduce the PSU count to 2. That is 1xPC PSU and 1x24v AC which should provide increased PSU efficiency, save space and reduce heat. Additionally I have a bunch of 5 volt and 12 volt rechargeable devices that I would provide leads for in the closet. Therefore mobile phones, lanterns etc can be charged in the closet with no additional PSU's. So this all sounds good in theory but I suspect there are some gotchas. The obvious one is the PC PSU may be capable of destroying all the end devices in one go in the event of a fault. However, my experience at work is that PSU's tend to destroy themselves and the PC hardware often remains serviceable. Anyone rationalised PSU's in this way or any other experience or comments. Cheers Justi

On 10/20/2011 11:28 PM, Justin Richards wrote: > So I am entertaining the idea of using 1 ex PC PSU that provides 12v > 8Amp and 5v 20amp. > > > Anyone rationalised PSU's in this way or any other experience or comments.. > > Cheers Justin I have done what you are suggesting for my router, cable modem and voip adapter. They all used 5VDC and there was no point in using 3 adapters. I just bought a larger current adapter and put them all on it. I also have a wdtv live player, usb hard drives powered off a single 12VDC adapter , rather than the 3 it would take normally. Some devices are not designed to share grounds with other devices. My cordless phone would have audible hum if connected to the voip adapter and the same power source. It also would not ring while they shared the power ground. Otherwise everything worked out fine and things like routers, modems, hard drives don't seem to have any issues. Mark

On Friday, October 21, 2011 11:28 AM, "Justin Richards" wrote: > The closet has become the communication closet (much to my wifes > annoyance) Perhaps she could fit a nice new coat into that closet and your transgressions would be forgiven? Or does she have a hobby that could benefit from some more support? > So this all sounds good in theory but I suspect there are some > gotchas. The obvious one is the PC PSU may be capable of destroying > all the end devices in one go in the event of a fault. However, my > experience at work is that PSU's tend to destroy themselves and the PC > hardware often remains serviceable. "Often". My work PC about ten years ago died while I was using it. The screen went black, the power supply fan spun like a turbine, and I could hear capacitors and varistors popping. I reached back through the smoke and pulled the power cord out of the back. The power supply apparently lost its regulation and all the voltages shot as high as possible. Nothing was salvageable except the cpu, a Pentium III I recall, which apparently was subregulated by the motherboard. Bob -- http://www.fastmail.fm - mmm... Fastmail...

On Fri, Oct 21, 2011 at 12:13 AM, Bob Blick <spam_OUTbobblickTakeThisOuTftml.net> wrote: > My work PC about ten years ago died while I was using it. The screen > went black, the power supply fan spun like a turbine, and I could hear > capacitors and varistors popping. I reached back through the smoke and > pulled the power cord out of the back. > > The power supply apparently lost its regulation and all the voltages > shot as high as possible. Nothing was salvageable except the cpu, a > Pentium III I recall, which apparently was subregulated by the > motherboard. Cheap power supplies of that era regularly suffered that failure mode. I lost an entire PC in exactly the same way. Every PC I have built in the years since has gotten a power supply from a reputable manufacturer. My OCD side likes the idea of reducing all the extra power supplies. The pragmatist side says, if it ain't broke, don't mess with it. -p.