I appreciate that this sounds really odd. My laptop is a Dell XPS with a metal skin. If it is plugged in, when I run my finger over the surface of the lid, my finger feels like it is running over a slightly fuzzy surface. If I unplug the USB power supply, the surface feels very smooth. Today, I asked someone else in the pub to do the same thing, charging and with the usb lead removed. He confirmed that I am correct and not totally bonkers. Why would that be?
Fuzzy feeling from laptop lid
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Power supplies have a class Y suppression capacitor from the primary to the secondary of the transformer.
If this is nearly failing it can pass some high DC (a bit AC ish) voltage to ground of the charging port which then connects to the metal frame of your laptop.
Are you using a charger of a known brand? If not then that'll explain why. Cheap power supplies manufacturers ignore these safety factors and install a non class Y safety capacitor.
If your power supply primary input has a connection to ground, then inspect that and check if it's not disconnected as class X capacitors do suppress harmonics to ground.
If this is nearly failing it can pass some high DC (a bit AC ish) voltage to ground of the charging port which then connects to the metal frame of your laptop.
Are you using a charger of a known brand? If not then that'll explain why. Cheap power supplies manufacturers ignore these safety factors and install a non class Y safety capacitor.
If your power supply primary input has a connection to ground, then inspect that and check if it's not disconnected as class X capacitors do suppress harmonics to ground.
Does the mains supply into the power supply module have an Earth connection ?.
Without an effective Earth the internal circutry will float. Capacitive coupling will pull that floating crcuitry to a potential between Live and Neutral, typically about 125 Volt above Ground, mid point of 0 and 230 but this depends on the ratio of capacitor values. (*)
The potential on the internal circuitry will be capacitively coupled to any metalwork and current flowing though this capacitive coupling and into a finger is the cause of the fuzzy feeling, The amount of capacitive coupling is ( should be ) small which limits the current into fingers to a non hazardous level.
(*) If there is an Earth connection to the power supply module and Live and Neutral are correctly connected then ( in theory ) the ratio of capacitance to Live and capacitance to Ground is such that the potiental on the floating circuitry is pulled very close to Ground,
Without an effective Earth the internal circutry will float. Capacitive coupling will pull that floating crcuitry to a potential between Live and Neutral, typically about 125 Volt above Ground, mid point of 0 and 230 but this depends on the ratio of capacitor values. (*)
The potential on the internal circuitry will be capacitively coupled to any metalwork and current flowing though this capacitive coupling and into a finger is the cause of the fuzzy feeling, The amount of capacitive coupling is ( should be ) small which limits the current into fingers to a non hazardous level.
(*) If there is an Earth connection to the power supply module and Live and Neutral are correctly connected then ( in theory ) the ratio of capacitance to Live and capacitance to Ground is such that the potiental on the floating circuitry is pulled very close to Ground,
If the power supply was manufactured with an earth connection then of course the designer would have installed the "appropriate capacitor values" unless if its a very cheap design then it may have been omitted/not designed properly.
Thanks for the reply. I am currently using the laptop (plugged in). The fuzzy thing is not evident. I suspect that is down to the fact that the battery is currently fully charged.
The charger is made by Monarch. It is about 7 months old.
65W USB-C PD Home Charger UK
Power up your devices with our 65W USB-C home charger. It is engineered with the latest USB-C Power Delivery and PPS technologies can provide efficient, fast, and safe charging for a wide range of devices. Key Features: Supports 65W PD fast charging 5V/3A/15W...
www.monarchgadgets.com
The wall wart charger has no earth. The earth pin is plastic.
Thanks.
I have never seen a laptop charger with an earth.
I think I almost understand what you are saying- I wasn't concerned.... however, although the battery is currently charged (with the lead plugged in), I popped of to the loo and put some tracks on the jukebox. The fuzziness was back, until I opened the screen. Then it disappeared. Admittedly, now I think about it, the fuzz is possibly only when the lid is down, and only under certain circumstances.
I don't want to turn in to DiyNutJob but I cannot recall experiencing it when I used to use the official Dell barrel charger (which no longer works- a pint got spilt on the laptop whilst it was plugged in using the official charger, hence I now use a USB-C charger).
I am not contradicting the information given above, but there are other explanations/viewpoints.
I definitely have seen laptop chargers with an earth connection – these have “kettle” leads (IEC C13). Whether the internals of the charger actually connect to that earth is another matter. Also, the UK adaptor for Apple laptop chargers also has a metal earth pin - again whether the charger itself makes use of that is another matter.
With some metal laptops (Apple anodised aluminium), you do get a “fuzz” feeling when running your fingers over the surface – whether they are plugged-in/powered/sleeping/off.
However, I’d get yours tested.
I definitely have seen laptop chargers with an earth connection – these have “kettle” leads (IEC C13). Whether the internals of the charger actually connect to that earth is another matter. Also, the UK adaptor for Apple laptop chargers also has a metal earth pin - again whether the charger itself makes use of that is another matter.
With some metal laptops (Apple anodised aluminium), you do get a “fuzz” feeling when running your fingers over the surface – whether they are plugged-in/powered/sleeping/off.
However, I’d get yours tested.
As long as the charger is a legitimate brand and CE marked, there is little to worry about - the class Y cap will pass a touch current of a fraction of a mA.
This tends to be a 'thing' when aftermarket chargers are used.
For example, the official charger for the Unibody Mac, appears to be Double Insulated, but has a kOhm resistor connecting the earth to the Gnd in the PSU and several high value resistors connecting the Gnd, to the body of the laptop.
I've experienced the tingle on Macs with aftermarket PSU and even with an official PSU, that has been used with a 2 pin plug adapter.
The OEM parts are also often better specified, with tighter control of components (adding cost), allowing for an acceptable touch current whilst minimising RFI - especially true if the appliance is a medical device.
It's unlikely that any component is failing, or the device is dangerous; its more likely that the OEM part is better specified and it may also have had a link to the earth - most of the dell laptop chargers I have dealt with have a cloverleaf 3 pin mains connector on the power brick.
Edit:
1KOhm earth to Gnd on a Dell USB-C charger, I have here...
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I've experienced this in the past and some time ago attempted to measure the current - it was way down in the "not a raliable reading" level.on my not very high spec multimeter. Apple's supplies are earthed if you use the power cord, but not if you use what they call a duck-head adapter.
Another factor to bear in mind is that you only need one connected peripheral to be earthed and that will earth everthing else - since most interfaces (ethernet excepted unless using screened cables) connect a screen between the bodies of the connectors.
Another factor to bear in mind is that you only need one connected peripheral to be earthed and that will earth everthing else - since most interfaces (ethernet excepted unless using screened cables) connect a screen between the bodies of the connectors.
The official "duck head" adapter is earthed as well, through contacts in the rear slot.
This is what I meant when I said...
The third party (eBay special) duck head adapter had a plastic earth pin (and had a fake fuse holder with no fuse
), hence a small tingle, even with the official PSU.It's also possible to plug in a figure of eight DI power cord into the MagSafe PSU, so I don't think Apple are particularly bothered whether it is earthed, or not!
And just to add, if Opps can find a friendly PAT'ter, a touch leakage of less than 0.25mA would be deemed a pass.
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The 'fuzzy feeling' is common, when you contact any unearthed conductive part, of many things. It is just a bit of leakage, or induced voltage, usually nothing to be concerned about. There will be a measurable voltage, when measured against an earth, but there will not be enough current behind the voltage, to be a concern.
And from where do we obtain the earth from?
From anything or ony body what is near to the real earth ( the ground ) and is therefor capacitively coupled to the Earth
Yes, but the power supply is isolated from true earth, isn't it?
No, it's connected to the mains, one side of which is earthed. The filters and parasitic capacitance will generally pull the secondary side (output) towards half the mains voltage (i.e. 120V for us) relative to esrth.
As we have a weak link to earth (again, mostly capacitance), there is a very weak circuit through our body.
As we have a weak link to earth (again, mostly capacitance), there is a very weak circuit through our body.