The standard power adapter for Apple laptops is a work of art. The Magsafe connector has saved more than one laptop owned by the Hackaday crew, and the power brick with interchangeable plugs for different countries is a work of genius. Being a miracle of modern manufacturing doesn’t mean Apple gets it right all the time; the UK adapter doesn’t use the ground plug, leading to the power supplies singing at 50 Hz when plugged in. [Gareth] had had enough of the poor design of his charger and decided to fix it.
The Apple power adapter has two obvious connections, and another shiny metal disk meant for a connection to Earth. In most of the Apple charger ‘extension cords’, this earth connection is provided by the cord. In the smaller plug adapters – even ones where space is not an issue, like the UK plug – this connection is absent.
To fix this glaring oversight, [Gareth] shoved some aluminum foil where the earth terminal on the plug should go. A hole was drilled through the plug to connect this foil to the Earth socket terminal, and everything was covered up with kneadable epoxy.
No, aluminum foil probably won’t do its actual job of preventing horribleness in the event of an insulation failure or short. It will, however, silence the 50 cycle hum emanating from the power adapter, and that’s good enough for [Gareth].
“interchangeable plugs for different countries is a work of genius” wait what ?!
If you’ve ever seen one of their stores, Apple has a very low standards for the definition of “genius”.
Now it won’t be long until somebody 3D-prints a proper plug for UK =)
Will be expensive, as there are only very few 3D printers which can handle metal and even fewer which can handle metal and plastics in one machine.
So this muppet thinks he’s smarter than the combined intelligence of Apple, Delta, UL and certification engineers? The earth pin is left unconnected for good reason.
If there were any more remaining doubts that he’s an idiot he goes on to use aluminium foil as a ground connection…
“The earth pin is left unconnected for good reason” then why does the longer Apple cable that comes in the same box have it connected…? You have no idea what you are talking about. Aluminum is fine for the amount of current that causes the 50Hz hum. This guy may not have more intelligence than the engineers, but he’s sure a lot more intelligent than you.
OK so you have
1) a plug attached directly to the power supply
2) a plug sitting at the end of a long-ish cable
You can’t tell there’s a real difference between the two? Hint: it’s related to Engineers’ Main Curse (EMC)
Serious question: From an engineering point of view, what is the harm in connecting the earth pin in the non-cabled version? My intuition would lead me to believe that earthing the power supply should reduce EMI under all conditions. If this isn’t the case, I’d be curious to know why.
You have to remember that engineering types are very dogmatic. They believe what they believe because they, as people of higher intellect, are clearly right. They do not need a rational reason. Of course this does not hold to the majority, only those that hold emotional reactive attitudes when their views are questioned.
Same reason why so many terrorists or otherwise radicalized people hold engineering degrees.
Yeap. EMC test (specifically the conductive EMC), BOM cost and the size savings are why they are doing it.
I have done EMC filter design and have to deal with the test (which I passed first time), so I am well aware of the issue.
I know what you’re saying, but I have a hard time imagining what that reason might be. Reason I say this is because Apple sells both earthed and non-earthed plug options available in the same regions. Why not just earth them both?
Some bean counter probably realized they could save $$$$ by not including it
Right, the whole power supply is highly over-engineered and then someone decided to skimp on a little bit of metal. Sure, makes sense.
It does.
Never worked in manufacturing, have you?
It’s also the reason why ‘good’ brands put crap capacitors in their power supplies. They’ll last past the warranty period and we save 25 cents per unit, score!
(I think everyone uses crap capacitors these days.)
If you buy the same product for few years you can see this in action, it’s rather fascinating. (Sometimes the changes are good.)
Actually it does make perfect sense, unlike your comments. Once in a while you should leave the comfort zone of your armchair and venture out into the real world.
Then I’d be interested to know, since you seem to know all, why it is that Apple sells cords for these adapters which contain a working ground connection but the short “stubby” ones that don’t have a cord are completely lacking in a ground connection despite actually having a pin that goes into the outlet’s ground.
Considering I know people that have received electric shocks from the casings of non earthed macbooks on charge, I think apple are the muppets
Unfortunately, the reason for omitting the ground plug isn’t for safety. I am guessing it is so that they can pass FCC type of conductive EMC test without having to have a proper common mode filter on the power supply input and probably save themselves the cost of the parts + size.
There is leakage current coming from unbalance coupling inside a transformer. In the old day when they build power supply with a Earth ground, they use a commom mode filter which blocks the current and a pair of Y cap where this current can forced to go to Earth ground. No actual ground connections means that there are no path for common mode current to go *during* the test. That however doesn’t mean the common mode current won’t try to find a different way in real life usage e.g. grounded peripheral(s), or you touch the metal part of connector housing etc.
http://www.marcspages.co.uk/pq/3333.htm
These currents come from the use of Y-capacitors. Stray capacitance in transformers is much lower. Even on double insulated devices you are allowed to have some Y capacitance (1 or 2 nF), which got to the OUTPUT GND wire and gives this annoying shocks.
So I think, the plug and the cable was designed by two engineers/teames, they just forgot the earth connection and it was “just good enough” to comply with regulations.
I have personally experienced the problem the author is mentioning: electric shock and the hum when using the short plug and the long cable fixes the issue. I have also submitted a consumer complaint in the past to the fair trading (here in AU). So regardless of who made this product, it’s faulty. I have not found a single other charger (even the cheap ones off eBay) that does this. I have also never seen a doubly isolated charger (indicated by a double square box symbol on the charger) to have an earth pin!
I am inclined to submit another complaint, this time with support from other affected users.
When you say Earth pin, you mean a metal one? Cos usually, as you probably know, they use plastic ones, since in some countries the Earth pin is needed to open the shutter in the mains socket that covers the neutral / live holes.
Why use metal ones that aren’t connected? Maybe they ordered a job lot of them, perhaps for an earlier design that would have connected to Earth, but then changed it later when somebody realised you could save a hundredth of a penny by not doing. Or pass certification easier.
earthing it can now set up a new problem.
ground or earth loop if the apple device is then connected to something that is connected to your tv cable or satellite dish system then you will get noise caused by an ac voltage on the ground loop .
Now now, we all know this MUST be a faulty design. There is no other explanation. Don’t try to justify it to this crowd.
Standard is for all UK mains devices to be earthed, never causes a problem with cable TV (which is unpopular in UK anyway) or satellite TV. A few phone chargers and apple adapters seem to be only non earthed devices, I know a few people who have suffered electric shocks from the casings of charging macbooks.
not arguing the standard — but as to shock from charging macbooks, that seems more likely to be a static electric skin transfer to me. I fail to see how grounding the AC side of a transformer would decrease the likelihood of a shock on the DC side (the laptop). Maybe my understanding of how transformers work is just completely faulty. I don’t claim to be an expert.
Nope, more laptops suffer from this, all (“surprisingly”…) without the earthpin…
Saw an Asus laptop (don’t remember the model) create over 50V of potential on metal parts of the chassis and several mA of short circuit current, you definitely felt tingling when you touched it. Wet hands would probably hurt. The PSU was sent back several times, all had this problem.
If you’re wondering how it’s created, don’t forget that you are dealing with a switchmode PSU running at several hundred kHz, at these frequencies even the smallest magnetic coupling produces a notable potential.
Also, whenever you have something with a conductive surface that is fed from mains, it should always be grounded just because if the PSU isolation fails (for whatever reason), it can’t kill you when you touch it.
I had a problem where I was constantly zapped by one of two Macbook Pro’s. Turns out it was getting a potential is it was plugged with earth-less plug, my the other was plugged with long cable with earth.
Current was constantly going from one MBP to the other through me…
It is not just a transformer, it is a switch mode power supply. This has EMC filters which contain Y capacitors – from the mains input to the (output)-GND. If this is not earthed you have about 110-120V with high impedance (1 or 2nF @50/60Hz) against earth GND.
This has NOTHING to do with static – except that is similarly annoying
Sky (UK satellite company) boxes are definitely not grounded, they use a figure of 8 connector.
Just like most class 2 electrical equipment.
> I fail to see how grounding the AC side of a transformer would decrease the likelihood of a shock on the DC side (the laptop).
Most people that don’t understand switch mode power supply and parasitic fails to see that. i.e. anything to do with real life parts or high frequency would require you to understand that. Too much simplification of common electronic components that you failed/care to understand or just don’t have the background/experience for it..
AN1679/D How to deal with Leakage Elements in Flyback Converters
http://www.onsemi.com/pub/Collateral/AN1679-D.PDF
Also google for “cause of leakage path in SMPS” Tons of technical material on the subject. This is not the stuff you don’t learn from watching youtube video.
Fair enough – you will note that I don’t claim a level of expertise that I don’t have. My skills are limited to the “fix what looks broken and make occasional mods on low voltage stuff” level.
Virgin media covers over half of UK households and has at least 4.5m subscribers, I’d hardly call it unpopular!
How many of them like the content?
They’re buying it for the Internet. Probably.
This isn’t possible. We all know that no genuine Apple product ever has a fault.
For $3000 you’d think they could at least get the power adapter right.
Forgive my ignorance here, but I’d like to learn something. My understanding was that since these block adapters are doing the conversion from AC to DC, any of the noise generated on on the AC side would be unlikely to be transferred to the DC side and thus the device. Am I misunderstanding this?
What’s your reference? Without a reference floating voltages do just that, they float. Powersupplies are imperfect they leak current and any sufficiently high impedance will latch on to anything as a possible reference including sometimes the 50Hz signal. It’s actually a very complicated concept with many causes, but if you’ve ever lifted the ground signal from amplifier and heard your speakers hum, or grabbed the end of an oscilloscope probe and watched your body mysteriously generate a 50Hz signal you’ll realise there’s more to it.
If anything you’d see 400hz noise from the SMPS, not 50/60hz.. This guy doesn’t know what he’s talking about, that’s why he says “While this is not necessarily due to a lack of earthing per se, if the adapter is earthed the problem disappears.”
In other words he has no ideia what’s really going on.
Modern switch mode power supply runs at quite a bit higher frequency than 400Hz (tens to hundreds of kHz). Higher frequency means smaller transformers, caps etc.
400Hz is aircraft supply and transformers are still huge for that frequency.
If you run your finger along the metal surface of an ungrounded appliance, you can often feel the 50/60 Hz hum.
That sounds safe
I think Trui means that there is a vibration to the casing, I don’t see how you could phycially feel a 50hz radio emission.
Unless there is a magnet embedded in your fingertip?
You’re not feeling a radio emission. You’re feeling parasitics working their way through and an actual (but low) current travelling through your body. It gives you a nice tingling sensation.
Actually he mentions that it is 50Hz according to his multimeter, and he says it’s not necessarily due to a lack of earth because it is a floating output adapter, but nonetheless earthing it solves the problem. I think your ego was damaged in the above post where you got shot down and now you are just trying to make it better. You are wrong, get over it.
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Sounds good. I into this problem when using scope with
old laptop and had to replace parts because the mains
leakage from the laptop fried the scope.
Maybe conductive Epoxy would be better though and
mark it “ESD Ground” ???
Not connecting the power adapter to ground may have been a bad design decision by Apple. However, as it happens in most places, if the local law does not require something to be done–according to regulations–a company might leave out a feature because they aren’t required by law to implement it.
Bottom-line: A company, not just apple, will leave things done in a half-assed manner, in order to save money.
NOTE: I believe the US electrical code, maybe other countries as well, is vastly different than that in the UK.
Furthermore, if a minimal amount of current were to flow to ground and it would be enough for the aluminum foil to survive, then if it solves the problem…more power to you.
Here’s a quote from me: If it ain’t broke don’t fix it, if you do fix it, and it works … then it works.
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