PC PSU for networking equipment?

Discussion in 'General Electronics Chat' started by HKPolice, May 3, 2014.

  1. HKPolice

    Thread Starter New Member

    Oct 10, 2013
    3
    0
    I have 2 modems, 2 routers & a VOIP device all on the same table in the basement and the AC adapters for them are starting to die off. I've had 2 go within the last 2 years. Since they all use either 12v or 5v DC inputs, I was thinking about hooking them up to a PC PSU instead which has 12v & 5v outputs and a lot less ripple/better regulation than cheap AC adapters.

    Would that be an issue? I thought about it a bit more and I know that using a common ground with sensitive audio equipment can cause a feedback loop. What about networking equipment? Would sharing the same power source cause some kind of interference or short over the CAT6 cables?

    Thanks in advance!
     
  2. Brownout

    Well-Known Member

    Jan 10, 2012
    2,375
    998
    The 5v output will be low amperage. Add up all your 12v and 5v current requirements and make sure the PS will provide enough current on each rail. Other than that, you should be fine. To avoid ground loops, use good layout/connection methods and filtering.
     
  3. #12

    Expert

    Nov 30, 2010
    16,252
    6,750
    Your worries are without merit. Internet frequencies are so far from audio that you'd have to work at it to make a ground loop problem. The modems and routers have capacitors inside them that should take care of cleaning up any power supply noise.
     
  4. paulktreg

    Distinguished Member

    Jun 2, 2008
    609
    120
    The +5V output on any decent ATX power supply will be of the order of 25A~30A so it won't be a problem.
     
  5. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,136
    200
    I'd like to interject and be slightly off topic. So, far I haven't lost any network stuff that wasn;t connected to a surge suppressor. That said, MOST of my network stuff is now on a UPS.

    I did have issues with wall warts falling out, so I placed them on octopus cables and they lie on a shelf. All ends are labeled with things like 5 V 1A (5.5/2.1) C+ and the adapters are labeled as well.

    I lost a Slingbox power supply and a repeater power supply that was not protected and on 24/7. The repeater died when a neighbors oven control died,

    I did loose a DSL modem itself and it was on a 9 VAC wallwart and operated on 12 VDC POE. I don't know what killed it.

    When I did commercial stuff, my favorite suppressor was the Trip Lite ISOBAR, I did see one toast and the connected equipment warranty honored.

    For contingencies, I did buy a few of these: http://www.aliexpress.com/item/5-PC...20V-Constant-Voltage-Voltmeter/609668731.html from ebay.

    It;s basically an adjustable buck converter with V and I meters and current limit. I put it in a box with both a 5.5/2.1 and 5.5/2.5 coax inputs and an Adapt-a-plug output. So, now, I'm in a position to create what I need with minimal effort. Input polarity can easily be changed on the terminal strip and output polarity can be changed there or on the adapt-a-plug tip. The power isn't isolated.

    I have been running the Slingbox on the supply for at least a year. A 6V supply was purchased for like $4.00 from ebay, but not used yet. www.powerstream.com has some nice adapters.

    So, I too looked at the power supply mess: surge suppressor, UPS, a quick fix adapter and the octopus cable.

    As art of a planned upgrade I will have a device that uses a 17 V, 1+ Amp wall wart and probably one (serial server) that uses 24 VDC.

    Ethernet devices are essentially isolated because of the Ethernet magnetics so they will not be an issue operating off a single supply. USB devices however may have troubles and so might serial devices. USB isolators are too expensive.

    One of the other ideas I had was to use multiple meanwell DIN rail supplies. http://www.trcelectronics.com/Meanwell/din-rail-power-supply-mdr20.shtml with a kinda mix and match. The case and various outputs, strain reliefs polarities sharing, current limiting etc. just made the prospect yucky.

    So, the real word is to protect and make sure that the wall warts have good solid connections and are surge suppressed and I have the ability to make a replacement supply if I have all the adapt-a-plug tips. Radio Shack has a decent supply. My networking stuff hangs out in the ceiling.

    A UPS is better. I have two UPS at home, one runs the phones, answering machine and provides secondary backup for an emergency response system. The other runs my network. One was free and the other was bought at a thrift store. Both needed batteries.Neither work if the batteries are dead. I need the UPS for a RAID server.

    For very robust power, a ONEAC power conditioner and a surge suppressor is fantastic,

    The "back burner" has lots of stuff planned. Wired patch panels. Better wired connections. Upgrade to wireless ac networking and hopefully 3G backup and an automation server.

    Now, I am considering building a low voltage UPS with 4 non-isolated outputs, Part of the reason is I want a specific form factor to hide in the living room. The main use will be for the repeater, It's 5V now, but the new one requires 17 V.

    Your ATX solution may consume too much quiesent power. It's still more important to provide surge protection. That should be your #1 priority. The modems may need isolated power. Not sure if they are cable or DSL? Anything with Ethernet only should be OK.

    The meanwell solution might work for you.
     
  6. HKPolice

    Thread Starter New Member

    Oct 10, 2013
    3
    0
    Thanks for the input guys. I wired them all up last night and it's working great. I have a PC NAS under the same table so I just spliced all the DC plug wires to a molex connector.

    I have an APC Smart-UPS 1500 running everything including the ac adapters that died so it wasn't damaged by surge or dirty power. They're just cheaply made switching power supplies and maybe putting them on the same power bar caused some kind of degradation from the EMI. They did last a good 5yrs+ before dying so I guess I can't complain too much.

    I'm glad to have switched to a PC PSU because while looking into getting a big 5a 12v power brick, I found out that even reputable models are spec'd for 240mV+ of ripple. The ATX standard is spec'd for 120mv max on 12v and my Antec PSU (made by seasonic) has less than 20mv ripple under low loads according to online reviews. This cleaner power should hopefully make things more stable in the long run.
     
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