Can a pile of consumer electronics be powered from a single supply?

Discussion in 'General Electronics Chat' started by strantor, Apr 7, 2015.

  1. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    I've migrated most of the electronics from around my house to one central mothership cabinet. Right now in my cabinet I have two full power strips to accommodate all the wall warts for all of this crap:
    HDMI splitter
    Router
    Cable Modem
    DVD Player
    Karakoe Box
    Laptop
    NAS
    USB hub
    POE Ethernet Switch
    IP Camera
    USB over IP Device Server
    Projector
    DVR

    I'm thinking of adding a couple of more gadgets to the mix:
    IR Blaster
    Raspberry Pi
    Printer

    It already looks like a mess, and adding a 3rd power strip would put it over the top. All of these devices operate on 12VDC or 5VDC. I'm wondering if I am likely to encounter any problems if I were to chop off all the wall warts and power everything from one or more large ATX power supply(s). I'm concerned about making supply voltage common to devices that communicate with each other. For example, with the HDMI splitter, DVR, and Projector all being powered from the same supply; in the absence of the isolation provided by the host of wall warts, is there a chance that the Splitter, DVR, or Projector shorting one another out through the HDMI cables?
    Is there increased chance of noise?
    What issues could I face in doing this?
     
  2. MrChips

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    Oct 2, 2009
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    I don't see a problem except the heavy current draw. Use a star configuration or make sure you use heavier cabling such as 10-12 AWG for bus runs.
     
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  3. MikeML

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    Huge potential ground loop causing hum.

    Also, before adding each item to the mix, you need to determine that 0V from each device is connected to the ground side of any other input/output connection to that device, because after you cut off the wall-wart, you will effectively short all the 0Vs together...
     
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  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    there is already a common power supply for these, the ac outlet on the wall.
     
  5. MikeML

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    Yes, but each wall-wart effectively provides transformer (Ohmic) isolation between all the components. Throwing away the individual wall-warts and replacing them with one big common DC supply forces you to connect all of the individual oV nodes to a common oV output from the supply (actually, all of the +5V nodes have to be connected, too). This introduces a potential common-mode noise voltage on each of distal components because of the IR drops along the individual wire runs back to the power supply.
     
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  6. MrChips

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    That is why I suggest a star configuration. Two wires, Vsupply and GND, for each load goes all the way back to the power supply.
     
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  7. MikeML

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    That doesn't eliminate ground loops, just minimize them. Suppose you have two items A and B, each with its own ground wire going to the the supply. Wire A doesn't carry ground current for B and vice versa (good). But the common-mode voltage between A and B is still the IR voltage drop across ground wire A + the IR voltage drop across ground wire B (bad).
     
  8. #12

    Expert

    Nov 30, 2010
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    Without reading the thread:
    I did this for a guitar player with lots of different stomp boxes. The method was to make a bipolar +/- supply and use those 2 row pin headers with tiny jumpers to assign each output positive center or negative center. It worked.

    Just a hint. Might work for you, might not.
     
  9. Hypatia's Protege

    Distinguished Member

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    Not that it's any of my business, but why??? --- Just curious...:)

    Best regards
    HP
     
  10. strantor

    Thread Starter AAC Fanatic!

    Oct 3, 2010
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    So that if someone breaks in, they will get all my gadgets all in one convenient place without hunting. Also so that if something catches fire, it will burn my entire system.
    </sarcasm>

    The reason is mainly because I'm lazy. This is a work in progress home theater/home automation project. I want all my network devices hardwired but I don't want to crawl around in the attic running Ethernet cables.

    Also I have two toddlers and they are fond of rooting around in cables and unplugging things and chewing on power conductors. The less things I have plugged into the wall at toddler level around the house, the better. The more things I have protected inside a locked cabinet, the less things I have plugged into the wall around the house.
     
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  11. RayInMS

    Member

    Dec 12, 2012
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    This may not be what you're looking for...but have you considered fabricating a custom power panel that you could mount inside the cabinet? Outlets are cheap at most Lowes/HDs, or can be had on Amazon (these panel mounts are nice). Maybe use ABS plastic sheets or get someone to (3D) print you a custom enclosure. Bring power into the enclosure from a single wall socket. That way, you can position the sockets so your wall warts aren't on top of each other. Cable ties make things tidy. This way, you keep your supplies isolated via their respective transformers.
     
  12. alfacliff

    Well-Known Member

    Dec 13, 2013
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    having one power supply for everything could be bad, what if it fails? one good voltage spike or overvoltage failure could kill all of your stuff.
     
  13. Dr.killjoy

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    Apr 28, 2013
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    I am pretty sure he has enough common sense for that style of protection..
     
  14. ian field

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    Oct 27, 2012
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    An easy way to get started; is concentrate first on everything that's USB powered. I've seen USB wall warts up to 2A, but with a bit of home construction you could build up from a surplus open frame switcher - look for one with at least 5A 5V output. At the very least you should also get a +12V rail, you can use that for some 12V devices - but as someone else pointed out; you have to watch for how the grounded parts are connected inside the device.
     
  15. Reloadron

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    Jan 15, 2015
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    Using an ATX PSU I can see it working just fine with due consideration to Mike's post regarding potential ground loops. I would also give some consideration to fuses. You come off the + 5 and +12 volt rails of an ATX PSU and I would add a fuse block with fuses for each load. Something like this for a fuse block:

    Fuse Block.png

    One for 12V and one for 5V bus lines. This way each device is properly fused.

    Ron
     
  16. alfacliff

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    there are a lot of people who get their tv, phone, internet and such all from the same source. now realizing that one failure will cause thm to not be able to get their internet supplier to report the failure. same with a power supply, they fail sometimes, and all the consumer electronics is off till its going again, even if it dosnt kill various thiings. also, a common point for a lightning strike to destroy most or all at the same time.
     
  17. tcmtech

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    Nov 4, 2013
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    Given all of the devices are in close proximity to each other and all sharing common power and ground lines I don't see where it will be much of an issue. As far as ground loops go I do not see much on your list that are actually analog audio signal carrying devices and the rest are digital devices that will likely already have the necessary internal signal isolating components in them if they needed such protection.

    Over the years and doing experiments with my home theater plus numerous other computer network redesigns so far I have never had a problem combining several smaller load devices to one larger power pack so I say give it a try!
     
  18. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I'm not buying the lightning strike theory being all the devices are already sharing common physical connections between each other through their network cabling and so far I have never considered the cheap wall wart power packs to be all that great of lighting protection system any way.

    What I am saying is "what if XYZ bad things may happen" is not a very good excuse for not trying to improve or learn things from.
    I mean heck "what if" you have a stroke heart attack or get hit by a meteorite in the next few minutes and die? All that worrying about the future negatives would have been for nothing! :p
     
  19. Reloadron

    Active Member

    Jan 15, 2015
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    This has something to do with all the eggs in one basket? :)
    Always have an alternate plan B.

    Ron
     
  20. ian field

    Distinguished Member

    Oct 27, 2012
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    There are some gotcha's with using an ATX PSU - you have to adequately load both the +5 & +3.3V outputs, or the others will sag under load.

    When I repaired PSUs for a living, I had a nasty problem with a cheap low rated ATX PSU - not all the 3.3V connector pins actually carried power, one of the pins had the voltage sense wire all to itself. The connector on my test load didn't anticipate this and the unit was powered up with no connection between the 3.3V output and its voltage sense wire - the PSU went bang!

    Since then; any time I make up a dummy load, I take the snips and cut the power connector out of the scrap board rather than unsolder the connector - that way, the PCB traces automatically group all the pins that need to be connected together.
     
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