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Discussion in 'Electronic Components' started by ehsjr, Feb 19, 2007.

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  1. ehsjr

    ehsjr Guest

    Power Strip Liberator

    I believe this product has been mentioned before
    in the newsgroups. It's good enough that it bears
    repeating. It is a ~1' long extension cord, that
    allows you to plug a wall wart in without covering
    other outlets on your power strip. You can have your
    DSL modem, router, amplified speaker and whatever
    else all plugged in to a strip, with the other strip
    receptacles still accessible. Cyberguys (link below)
    sells them, as well as other places.

  2. ian field

    ian field Guest

    Personally I prefer the surge protected strips sold by the local Focus DIY
    store in 4 or 6 way strips for £8/£10 respectively, both the PC desk and TV
    stack have them, I consider the regular 2meter lead to be a useful addition
    of common mode inductance. If the wall-wart adapters crowd the plugs out, I
    just buy more surge protected strips and increase the protection.
  3. Guest

    Make your own powersquid...
  4. Palindrome

    Palindrome Guest

    I simply put in a whole-house filter and surge arrest system at the
    consumer unit. It is bonded to the protective earth at that point. I
    also have an online UPS, feeding its own ring main.

    But then, my mains electricity comes on poles across Dartmoor.
  5. Rich Grise

    Rich Grise Guest

    Why not just buy one that has room for wall warts? e.g.:

    (there are lots of other brands and styles - just go shop around.)

    Good Luck!
  6. Makes sense, but I have a totally different take on it.
    Why not settle for some kind of common standard that means manufactures
    can't exploit the public with high-cost warts of unusual voltage, polarity,
    whatever they can do to make their wart vital and another wart useless?

    Given the amount of warts, and the amount of waste that results when they
    are not needed, isn't it time some standard was set? Governments are
    breathing down the necks of business, urging restraint in consumption. If a
    standard were made, people would get used to a single outlet with maybe 5V
    and 12V and a slightly different conenctor for each, like the DC jacks with
    2.1 mm or 2.5 mm plugs. Imstead of warts, there's by small cables and
    plugs, cheap and standard, and a single strong PSU with a meter that let
    the user know if they were taxing it too much. It would always outlast the
    products it drove, and the product could always be plugged into a similar
    PSU anywhere.

    In short, co-operation is better than conflict if waste is to be avoided.
    The electronics world is full of successful standardizations like mains
    voltages, plug shapes, MIDI and other protocols based on specific
    connectors and signals. Sure, there are also obvious incomptibilites, but
    compared to those, the wall wart situation is a disgraceful rabble.

    I usually avoid them by buying stuff that will take an IEC mains connector.
    When I can't avoid them, I look for 12V or 5V capability, DC, postive on
    centre pin. If it won't take that, then the only way I'll buy it is if
    there is no alternative, and sometimes I'll modify it so it CAN use a
    standard PSU I have lying around, so I can avoid relying on something that
    is usually tatty, feeble, and expensive to replace with exact type.

    Most people would welcome a standard low-volt buss for home and office
    wiring. It works for boats, cars, planes, trains, wtf does it not work for
    houses? Obviously it can, so it should, and the waste dreck of plastic and
    steel would visibly decline within months of establishing it.

  7. It's $2 plus shipping. I can buy an extension cord with three outlets at the
    dollar store. That lets me hook two or three warts to one outlet for $1
    instead of $6 plus shipping!


  8. Greetings,

    Yes, they are handy. Be warned, however, that not all are UL listed.
    (AFAIK, the ones I purchased some time ago from Cyberguys aren't,
    sigh, but the new ones seem to be.) They also may be available from
    your local drug/hardware/misc store. I believe I saw some under the GE
    brand, but I'm 100% sure the only connection GE has with them is in
    sticking the GE name on them.

    Outlet Strips:
    I recall reading that surge protected outlet strips in plastic cases
    are responsible for quite a few home fires each year. I also don't
    believe that UL listing is as strong a guarantee of safety as one
    might hope. Anyone considering purchasing one -- especially one of
    those high-priced, brand name designer pieces of Chinese cr#p --
    would, IMHO, do well to consider purchasing a Wiremold "Perma Power"
    unit instead (Manufacturer (Wiremold): ; one
    distributor (Mouser): They cost no more
    than the Chinese units, but are (were?) USA made.

    Richard Kanarek
  9. Joel Kolstad

    Joel Kolstad Guest

    If you've been purchasing consumer electronics in the past few years, you'll
    have noticed that 3.3V is becoming a popular regulated output voltage as well.
    That's part of the problem: You'd really need to give people adjustable power
    supplies from at least 2.5V-18V -- if not 0V-48V -- and get everyone to agree
    on the "programming" standard that sets that output voltage. (Granted, it
    could be as simple as a resistor.... although as soon as you let some
    committee work on it, they'll come up with something fancy like PoE, which --
    usually -- works well and is -- reasonably -- cheap due to all the logic being
    in a single IC, but it's actually a rather complex protocol for what's
    inherently a simple idea... it often adds $10+ per Ethernet port on a switch!)

    Another problem you have is... who's responsible if a product dies due to
    being fried? Could you ever demonstrate that it was the "universal wall wart"
    that fried the device if said UWW appears OK now? Even if you could, do you
    think the UWW manufacturer is going to replace the $200 media box it just blew
    up? Of course not.

    If you've been around awhile you're familiar with the old Tektronix TM-500
    series mainframes -- a large part of the attraction was the single power
    supply being shared by all the plug-in cards. Why did TM-500 go away? One
    significant reason was that the power supply started becoming a smaller and
    smaller cost of the product -- these days you can get a 40W Chinese import
    switcher for <$10 in quantity.
    [Cough!] Done much world-traveling lately? I'm thankful that most switching
    power supplies are now universal input (90-240VAC).
    Yeah, you have a point, but I think that "solving" the problem is
    significantly harder from a political point of view than you might think.
    There are -- or at least were -- small businesses that cater to RVers and
    truckers that make their livings modifying equipment for 12V operation. I
    have a suspicion that many of them have gone out of business due to the
    proponderence of cheap 12V-->120V inverters, though (you can get something
    like a 300W inverter for <$20, and while it's utter junk, in many cases it
    works just fine).
    Most people are utterly clueless about this sort of thing.
    It doesn't really... cars are 12V, yes, but other vehicles are 24V, 48V... the
    IEEE wants cars to transition to 42V... older vehicles were 6V... so there are
    always going to be more "standards" than you might prefer.

    To a certain extent I think this problem slowly is fixing itself, no
    government intervention needed -- people do seem to have a preference for
    power supplies that don't block adjacent ports on a power strip, and I believe
    a significant number will buy the product with the small switcher (that
    doesn't block the next port) over one with a traditional (linear) wall-wart.

  10. Bud--

    Bud-- Guest

    When MOVs fail they can overheat. In 1998 UL changed its standard (now
    UL1449 edition 2) to require overheating MOVs be disconnected.

    Connected outlets may be disconnected with the MOVs or stay connected
    without protection - the protector should say which option is used.
  11. Or shoot flames out of the top!


  12. A problem with a common supply is that often the gear is connected
    together and also shares a common signal ground. You will get nasty
    problems with ground loops, never mind the disasters of having some
    devices run on positive rails, and some on negative.


    Adrian Jansen adrianjansen at internode dot on dot net
    Design Engineer J & K Micro Systems
    Microcomputer solutions for industrial control
    Note reply address is invalid, convert address above to machine form.
  13. No-one knows more about the exact power requirements of a product than the
    people who build it, so for special needs they can add internal regulation.
    This is usually done anyway. There's not much difference between 3.3 and
    5V, just a little extra heat dissipation in the regulator when fed by 5V.

    I don't agree about the adjustable type. The point of standards is to try
    to remove the need for that, just as Joerg and others seek to remove the
    need for a product to be shipped with preset pots in it. Good design to
    established standards will reduce waste energy.
    Ideally, its maker. The mains supplier isn't responsible for repairing a
    110V unit plugged to 240V. Same logic applies. Also, up to a point, the
    user should be responsible. If a unit intended for a 5V buss is regulated
    with thermal or overvoltage protection, then plugging it to a 12V buss
    would make it shut off periodically and annoyingly, or perhaps do something
    more appropriate to warn the user to plug to a lower volt buss. Users would
    generally know that if in doubt, plug to the low-volt buss first.
    Connectors should be different for each buss, eliminating this risk.
    This cheapness of SMPSU's allows devices to have their own regulators in.
    Unlike linear types, it might not even matter which low-volt buss it's
    plugged to, or even if it's AC or DC, if it has rectification and smoothing
    built in. As this is no more than the effort and cost put into most warts,
    this ought to be doable. (I'd suggest a DC buss system though, things
    needing AC specifically are rarer and might best use their own
    Not much. :) This universal input thing IS a big step in the right
    direction, for sure. It will make it increasing painless to adapt to common
    standards in the future. If products needing low-volt DC input also had
    more of this, the standard low-volt buss becomes more feasible too.
    Yes. Which is why I'm saying this to engineers not politicians. If the
    politicians end up enforcing unenforcibles because the industry can't reign
    in its conflict-induced waste, things will be worse, not better.
    As a business like that is answering a need, it proves the need exists. I
    could rest my case right there, but that would be boring. >:)

    Going out of business as you describe means the need just got answered
    differently. All that's happening is conversion to ANY standard buss, at
    whatever cost. That's not just a need, it's a roaring demand! So there's a
    new motive, profit. If that doesn't make the industry sit up and watch, and
    think, what will?! They're small businesses, so I guess that's why. Most
    big things start small though. If the thing were addressed so it's easy for
    most people to get, it would grow enormously.
    Only because no thoughtful, simple standard exists. If the industry isn't
    willing to at least try, you can't blame the end consumer. Judging by the
    number and type of inquiries that clog the queues of Maplin and Radio Shack
    type stores, the consumer is really trying to find a way, and they are NOT
    being helped adequately. Maybe it's time they were given a simpler choice
    when they need to find sensible power supply and connector arrangements.
    Agreed, but if the product has its own regulation for anything other than
    standard 5V and 12V (the most commonly used in domestic locations), and
    protection against plugging to a higher voltage, then it will work.

    The question is which volts to standardise, and how many voltages. I'd
    suggest a maximum of three (24V, 12V, 5V), ideally just two (12V and 5V),
    because the biggest demand for clean DC voltages between 12V and 24V are
    for analog IC's. These are usually small-signal devices, or have their own
    mains supplies built in, and in either case, benefit from additional local
    supply cleaning anyway, so a tiny power converter running off a 12V buss is

    Almost all things of 5V and lower can run off 5V, with linear regulation or
    power converter on very small scale. Many things are designed to run on 5V,
    so it's extremely easy to adapt to. Same applies to 12V, hence my choice.
    6V and 9V are common, but 9 is easy, regulate off 12V. 6 is a tad harder,
    some things might need the 12V and waste a bit, most might be able to run
    on 5V well enough.

    Higher voltages like 48V are worth making a special case for, but it's just
    a variant on the same idea. In small cluttered places like homes and
    offices, few things demand voltages that high, and those that do either
    have their own mains inputs or can be made to work on 12V with a small
    power converter built in. As a wound transformer might cost more, it's
    worth doing. It's more efficient too.
    I'd hope that no government intervention will happen at all. But with the
    current pressures being put on industry, can you imagine they won't?
    They're already wreaking havok with CO2 emissions controls, and the sudden-
    ness of the demand to phase out the use of lead. The problem is fixing
    itself because it must.

    I'm only pointing out that trying to accomodate wall warts on a purely
    physical basis is the wrong way of looking at the problem. Most switchers
    for public consumption seem to be 5V or 12V output, unless you buy for
    something specific. This is good, it's as you say, part of the self-fixing
    effort the industry is making. All I'm saying is, why not go further, make
    more powerful ones, standardise connectors per voltage, NOT on some
    arbitrary way to make firm A's wart useless for B's product. That way the
    end user buys one per room, and anything in that room will plug into it.

    There are better ways to bring heads together than waiting for government
    to bang them together.
  14. That is true, BUT, if you look at any studio audio guide to best practise,
    you'll know of the 'star network'. As this requires that there be a common
    connection point for all supplies and grounds, a standard buss isn't the
    cause of trouble is it? It's the only correct basis for a cure.

    Solving of grounding problems per device is required, just as an end user
    should not be expected to break a safety ground to solve suck loops. It's
    the maker's problem. Again, if they knew there was a standard, they'd know
    what method of ground-loop prevention they'd need to use.

    The polarity thing IS a problem, and a very nasty one, too, but I've rarely
    seen a positive ground in a device that didn't do it either out of
    convenience, or an attempt to deny the use of a more standard supply. Just
    because arbitrary choices have been made, is no reason to ignore the
    problem. They MADE the problem, so exonerating the people who made it as if
    they have the last word is going to be counterproductive. Fortunately the
    positive-centre-pin is begining to win out. Personally I don't care which
    had won, as electrons flow from the other pole, but as the worst risk of
    damage is reverse polarity, this problem needs standardising ASAP! In the
    meantime, we can always use diodes. >:)
  15. Chris Jones

    Chris Jones Guest

    People seem to be using the USB connector as a 5V bus, and usually they
    blatantly ignore the current limit specification too...

    Ground loops are certainly a problem even now - my laptop has an external
    power supply which has an earth pin on the mains cable, and the negative
    terminal of the DC output of the SMPS is earthed at the power supply. With
    about 3 Amps flowing in the negative wire of the DC cable from the power
    supply to the laptop, the ground of the laptop is at about 50-100mV above
    mains earth. This voltage changes when the CPU or hard disk does
    something. When I plug the audio output into an external hifi amplifier
    with its own mains earth connection, all sorts of nasty sounds come out of
    the speakers because the laptop's ground is not at the same voltage as the
    amplifier's ground (and a couple of amps are flowing through the ground of
    the audio cable).

    What would be much nicer would be a power supply for the laptop with no need
    for a ground connection to the output side, and ideally something similar
    for the hifi.

    Since cables from your multi-wart are going to drop a significant amount of
    voltage anyway, I think it is not useful to attempt very close regulation
    of the output voltage. In that case, it might be quite feasible and cheap
    for each output of the multi-wart to be floating with respect to all of the
    others, since all of outputs could be derived from separate secondary
    windings on the SMPS transformer. If it is a small flyback converter, each
    winding would need a diode and a couple of capacitors, and the regulation
    could be based on just one of the outputs. Each output would not have very
    good regulation (but cable will ruin the regulation anyway), and the
    outputs would all be isolated, permitting people to ground whatever parts
    they want without the power supply causing any particular extra problem.

  16. Nice idea. I've considered the floating output too, it allows a star
    network ground without current induced voltage drops, and a cure for
    polarity differences, though only up to a point. It's still possible to
    common the wrong terminals through a chain of equipment, possibly with
    disastrous compound failures resulting. In short, separate isolated outs
    won't solve the problem of incompatibly chosen polarites, only agreement
    and co-operation can do that. (Or, possibly, litigation by the those
    adhering to the dominant standard against those of the other, in cases
    where deliberately chosen incompatibility causes another firm to lose money
    because of damage and lost customers).

    The current in a grounded supply negative can cause bother, I agree, but
    there are two ways to deal with it in current use. (I like bad puns). One
    is a coax DC line. That lowers the negative rail resistance enormously,
    reducing the voltage difference from negative to earth, and screens the
    positive line which is also useful. The other is a psuedo-balanced audio
    line. Even basic designs can use a common mode cancelling input to remove
    the noise, and a twin core shielded by a screen that is connected at only
    one end. The problem isn't really the use of a common standard with a
    common ground, audio gear manufacturers deal with this all the time, and
    they get by, and standards help there, the problem is when makers ignore
    standards founded in good sense, like those you mention who ignore the
    limits of a USB 5V line.

    Re the lack of useful regulation due to line losses, I agree, which is why
    I think local regulators will still be needed. My point is that it's no
    longer expensive to have a small room or house local buss for 5V and 12V. A
    lot of stuff will be fine plugged right in to one or the other with only
    basic protection against use with the wrong buss.

    I don't even think that any kind of standardisation needs to be drafted in
    some kind of comittee. All it needs is some firm to start punting them out,
    and people WILL buy them. It worked for the universal remote control. If
    end users can get their heads round that, they'll not have much trouble
    with a 12V/5V distributing board. It just needs someone willing to make
    them, and then other firms will want to make sure their products will work
    with them.
  17. Don Kelly

    Don Kelly Guest

    Lets see. 12V DC wiring over what distances? In a car it appears OK but with
    the increasing electrical loads in cars, there is serious consideration of
    higher voltages for cars. In a house, or in other than small aircraft and
    definitely not in trains- something like 12V is simply too expensive in
    terms of material costs and weight. The problem is that to get something
    sufficient to supply my computer, monitor, printer, scanner, speakers etc.
    requires a dedicated circuit equivalent, in terms of wiring, to at least 3
    standard 15A circuits (based on 180 watts at 15A, 12V). That is for
    equipment located at one place and doesn't allow for devices elsewhere . You
    will still need a converter and will also require more expensive circuit
    breakers than 120V AC needs. There is also the problem that, for most of
    us, with more existing house than retrofit funds, this centralized approach
    is out of reach.

    Note that mains voltage and plug standardization (or standardisation
    depending on the countries involved) have nothing to do with "electronics"
    standardisation except that the power utility standardizations determined
    the sources that the electronics industry standardized to. Note that the
    former "electronics" standardization of 117V (apparently +/- zilch) was a
    fiction that led to poor designs that couldn't handle normal variations in
    line voltage. The problem was resolved when it was realized by both
    utilities and electronics designers that there were normal variations along
    with one hell of a lot of crap coming in on the lines.

    Maybe wall warts aren't that bad- admittedly standardization of plugs and
    voltages is needed along with elimination of "in-between" sizes.

    rant returned with another rant :).
  18. 10 feet? One per room, on average. Considering the stupid proliferation of
    warts that is why this thread even exists, that seems like a good scale to
    work with. The total wiring thickness and length on that scale would be no
    worse than the wiring currently bringing low-volt lines out of those warts.
    Most of them are in one location, concentrated near a hi-fi or a computer,
    or a bed. People like to organise when things get out of hand, especially
    when the disorder is always in close proximity.

    The 'buss' need not be any bigger than a mains 4-way plug strip. You could
    fit a 200W PSU and lots of connectors on that, with a cost below £25, which
    given the wart count reduction, is a good spend.

    I agree with you about cars though, a lot of high currents there, it would
    save a lot of metal in switches and wires to use 24V. More is NOT a good
    idea. In a crash, there's enough deal with without adding electrocution.

    This is my rant. There are others like it, but this one is mine. >:)
  19. Or explode. We had some large block MOV's across some electrolytics in a big
    620V 150A power supply/charger. Occasionally we would get a start-up spike from
    the thyristor bridge that popped one, huge flash and bang and lots of smoke.

    Eventually found some high voltage elco's that obviated the need for the MOV's
    in the first place. The original elco's were failing through spikes which is why
    the MOV's were fitted!

  20. Looking under my desk, I see that we have a total of 12 X 240V 13A sockets, all
    occupied with various PC-related devices, plug-top PSU's taking half that number
    for the network router, modem, network switch, scanner and so on.

    Given that we have a decent sized PSU in the PC itself, why not have an
    auxiliary output from there to power all these PC-related items?

    A daisy-chained PSU lead could then run to all external devices.

    It'll never happen, but it would save a lot of floor space.

    Then there's the KVM leads.....

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