Leave it plugged in, or, NOT

Discussion in 'General Electronics Chat' started by Gdrumm, Apr 24, 2010.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Should the AC adaptor remain plugged into the wall after the device (cell phone, power tool, cordless vacuum cleaner, etc.) has finished it's charge?

    I've heard different views, and wondered if someone on the board knows the definitive answer.

    Thanks,
    Gary
     
  2. Bychon

    Member

    Mar 12, 2010
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    Facts: Wall warts use power when there is no load. Unplugging them stops this waste of energy.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    DEFINITIVE! Ac adapters use power with no load.

    The way a transformer works, it is constantly running power through the primary regardless of whats on the secondary.

    Feel them, if there warm, there costing you juice. Some of the smaller ones may not be warm, but they still use power.

    If your interested, do what I did. Get a few (or 1) of those Kill-a-watts. They plug into the wall and a device plugs into it. It shows draw, voltage, wattage, power factor, and all kinds of good stuff.
     
  4. loosewire

    AAC Fanatic!

    Apr 25, 2008
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    Kill -a-watts-Buy them at rome depot.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    The other thing is, the power is around 10¢ a month more than likely, so it is a personal decision of convenience.
     
  6. roadey_carl

    Active Member

    Jun 5, 2009
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    so the power being used when there is no load is the power it takes to run the primary winding?
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    As a general rule you should always plug out or turn off devices/light then not using them. The arguments will be both safety and environmental. This is good practice even if the device only use a small amount of energy. So saying like Bill. I do not care because the amount energy consumed is so small. Is quite selfish thinking. If we all take our part in conserving energy it will make some effort
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    Gee thanks, I love ya too!

    It is fundamentally a personal decision. In a year or so you might have used the energy that would have made an aluminum can. The term negligible applies here.

    Turning off the lights in your house makes a much deeper difference, and as anyone with kids knows it is an uphill battle.

    There are many ways to save energy, you are better off looking for the significant ones.
     
    myglaren likes this.
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    In transformers, yes. The two ends of the primary are connected to the pins on the wall. the two ends of the secondary are connected to the wire that you plug into the device. When no device is plugged in, the secondary is an open circuit.
     
  10. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    How does leaving it plugged in effect the life of the power supply?
    I've been told they last longer if you simply leave them turned on, and that by turning them on and off, you shorten the life of the adaptor.

    I've also heard that by turning them on and off, the repeated start ups use more energy than if you simply leave them turned on ( frequency of use being daily, or someting like that).

    Thanks,
    Gary
     
  11. retched

    AAC Fanatic!

    Dec 5, 2009
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    Thats true-ish.

    Some devices, like motors, require more power to start than they do to run.

    If a device took the same power to start as was required to run the device for 8 hours, and you needed to start it more than 3 times in a day, leaving it on would be an energy savings.

    If you are in Italy and you find a Rome Depot ;) get a Kill-a-watt and you can see this happen.
     
    myglaren likes this.
  12. Audioguru

    New Member

    Dec 20, 2007
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    My next door neighbour and I both got new electricity billing meters at the same time.
    Their LCD displays have huge numbers and I can see hers from my yard. After a few months, her electricity consumption is almost double of mine.

    She wastes as much electricity as she can. My wife and I save as much as we can.
    She is a retired teacher and gets paid the same high salary for her pension.
    I am a retired bum with only a low government pension.
     
  13. Wendy

    Moderator

    Mar 24, 2008
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    Truth, I don't know which is worse for the device. My personal inclination is that it will last longer if off, but turned on periodically. Many things electronic tend to rot if left off for years at a time, but there is wear and tear associated there too. Heat, even gentle heat, speeds up aging.

    I leave my phone charger plugged in full time, and plug my phone in when it is time.
     
  14. bertus

    Administrator

    Apr 5, 2008
    15,647
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    Hello,

    Most phone chargers are SMPS devices.
    I noticed they will break sooner when taken out every time
    and plugged in when it is needed.
    I leave mine plugged in as it is used for three phones.

    Bertus
     
  15. retched

    AAC Fanatic!

    Dec 5, 2009
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    The inrush will cause aging. If it were a "soft-start" it would slowly increase power during circuit close. That allows everything to come to temperature slowly, which will increase life. Avoiding the inrush current by leaving it plugged in will prolong the life of the wart.

    My brother and I had the same exact cellphones, and share a house. Same power, ect..
    When we started a contract plan, coning off pre-paid service, we got two of the 'free' phones that come with a contract. His was black, mine red. that was the only difference.

    His power strip that contains cellphone charger is on a wall switch as well as a lamp on his nightstand. When he enters his room, he flips the switch on. When he leaves, he turns it off. He does this dozens of times a day, some days.

    My charger is plugged into a non-switched outlet.

    His cellphone charger has died. Mine is still going. For a few days, he had to use my charger.. no big deal, but when he got a replacement charger, he left it plugged in and powered up 24/7 rather than a switched outlet.

    Not a scientific experiment by any stretch.

    There are outlets you can purchase for your home that connect to a master switch to disconnect power to the outlets. I wonder if these use a soft start, or straight on/off.
     
  16. Darren Holdstock

    Active Member

    Feb 10, 2009
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    I quite agree, and I'll admit it's a little disheartening to see popular myths reproduced on a technical board. The sad truth is that generally people will only do so much to reduce their personal energy consumption, and for many unplugging their mobile phone charger overnight gives them enough of a warm glowy feeling to be able to carry on driving gas-guzzling 4X4s. We're often not so smart, as a species, and it figures that if we're only going to do one thing to reduce energy consumption then that one thing is an utterly feeble effort and a complete waste of time.

    One variant of the myth I've heard is that mobile chargers use 45W. Of course they don't, that amount of power would melt the plastic in an enclosure that small, but I think I may have worked out where the misinformation came from. The original Nokia chargers were a simple transformer/rectifier/electrolytic arrangement, with the active charging circuitry being contained on the phone itself. On the back it gives the rating as 4.5VA, except that the decimal point was difficult to see, so it looked like 45VA. Now every schoolkid who's done physics knows that volts times amps equals watts, so 45VA = 45 watts wasted as heat, right? No, no, and no. For a start, that initially-correct 4.5VA is the maximum power transfer rating of the charger - much of that energy will be stored in the battery as charge. And when the phone is fully charged, the amount of power being lost as heat is negligible, as Bill quite rightly points out.

    If anyone has a Kill-a-watt meter or similar, you'd be lucky to see any reading at all when plugging in a mobile charger on its own. Try it. If you want to save domestic electricity, turn down the electric heating, wash your clothes at a lower temperature, don't leave your PC on all the time, turn off lights you don't need etc. And right at the bottom of the list, if you must, unplug your mobile charger.
     
    myglaren likes this.
  17. retched

    AAC Fanatic!

    Dec 5, 2009
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    Actually, the water heater and clothes washing temperature are BIGGIES. Not as big as your vehicle, but to tell you something interesting (kind of) Tide makes a cold water detergent that works as well cold as most do hot.

    If you always have to add cold water to your shower because the water is too hot, turn your water heater down, and use cold water detergent in the clothes washer.

    There you go. Warm fuzzy feeling, Clean clothes, no scalds, and a lower power bill.
     
  18. lordtimothy

    New Member

    Feb 7, 2009
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    There is a show where they bust myths and they did a spot on light bulbs. Myth was, uses more electricity to turn on a light bulb than what it costs to leave it on. Well the myth was totally busted even for the big ones. Quite interesting the results. I would say unplug if a long time will pass otherwise don't worry about it.

    Timothy
     
  19. retched

    AAC Fanatic!

    Dec 5, 2009
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    Leaving the cheap Made in China bulk chargers plugged in have resulted in fires. So regardless of the reason, unplugging is a good idea.
     
    PackratKing likes this.
  20. insta

    New Member

    Oct 30, 2009
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    0
    It's worth mentioning that while a transformer does always draw power, it doesn't draw anywhere near as much when it's idle. A high impedance on the secondary windings (ie, nothing to do) will cause a much slower flux through the core, which keeps impedance on the primary high. A high impedance means low current flow. I'd be surprised to see more than a watt or two idle power draw from wall-warts.

    A 5-watt parasitic draw, in Hawaii (most expensive power in the United States --$0.2671/kwh) will cost you $13 per year. I personally pay $0.08 in Kansas City, so I pay about $4 a year in wasted power per power brick I leave plugged in.
     
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