Posted on 07/10/2017 11:11:01 PM PDT by nickcarraway
3 dozen posts so far and no one has truly nailed this mystery of why the girl died. One major flaw is lack of real information. Is her unfortunate mother an electrical engineer?:
Her family says Madison was in the bath tub and grabbed her phone that was plugged into a charger in a bathroom outlet.
There was a burn mark on her hand, the hand that would have grabbed the phone. And that was just very obvious that thats what had happened,” O’Guinn said.
(end of snip)
Where is the comment from the qualified fire chief or the investigative officer who arrived on the scene telling the public for our own good what actually DID happen? What DID she grab, the phone or the charger, for example? Will the reporter try to find out from a qualified scientific mind what for sure happened?
We really don’t know what happened.
Do we today live in a world with SMART PHONES instead of SMART PEOPLE?
Or are there no true electrical engineers who bother with Free Republic who are real scientists who can make things clear on this science of cell phone chargers and are willing to offer intelligent comment to help the regular folk prevent loss of life and use tools safely within the limits?
(Or maybe they are waiting for more hard facts from the case, which is common among qualified engineering minds.)
Why not stick with the stupid phones and work harder on becoming SMARTER people in the meantime?!
Having trouble believing it happened as stated - unless the wall socket voltage was somehow applied there was not enough juice/amperage involved.
I was just thinking the same thing.
I was just thinking the same thing.
In most states you have to be able to show you can wire up a factory to pass an Electrical Contractors Exam. If you don’t pass the exam, you cannot legally even change out a wall receptacle in a house (there are a few small exceptions). So the system works to make it very difficult and therefore very expense to be a contractor...hence, rates well over $100/hour now.
As far as I know, there are no states with ‘limited’ contractors licenses, where they are limited to relatively simple 120/240 Volt work. If those licenses existed, perhaps this family would have been willing the pay the $50/hour (and maybe way less) to have a licensed person do a quick sweep of their house and change out defective hardware (which would including making sure there are GFCIs in the bathrooms, kitchen, basement, garage, and outdoors).
But that’s not the case, so most people (maybe not most FReepers, because most of us are real men, but most others), particularly metrosexuals, simply take what they get when they buy a house, particularly an older house...rather than take the risk of having a totally unscreened ‘handyman’ illegally do that work. And so we get these results.
You can't. That is, the voltage that is available is non-hazardous in the sense that it is fairly low in relation to the body's resistance. So, you shouldn't be able to push a fatal amount of electricity (say of the order of 20 milliamps through the body). Further, the charger should be double-insulated, which means it should be very difficult to pass current from the AC line to the charger output. (Double insulated products are considered safe enough that they don't have the third, grounding wire attached.
Of course, if the phone charger is on an extension cord, and the extension cord falls into the tub, all bets are off.
There’s a lot to be said for wireless phone charging, available with many recent phones (directly or with an adapter). No charging wire ever has to be plugged into the phone.
Her phone was plugged in charging or she was connecting it to the charger. It was the charger that killed her, not strictly the phone.
The iPhone chargers do use a transformer which isolates the 120 VAC input voltage from the 5 VDC output voltage and its lower 1 Amp current. The older chargers use a 120vac to 12vac transformer, a bridge rectifier to convert the 12vac to 12vdc, then use a 5v voltage regulator is used to limit the voltage to 5VDC. The isolation of the transformer prevents the shock hazard of house line voltage getting into the output.
However, the iPhone is quiet sophisticated. The iPhone power adapter is a switching power supply, where the input power is switched on and off about 70,000 times a second in order to get the exact output voltage required. Because of their design, switching power supplies are generally compact and efficient and generate little waste heat compared to simpler linear power supplies.
In more detail, the AC line power is first converted to high voltage DC by a diode bridge. The DC is switched on and off by a transistor controlled by a power supply controller IC. The chopped DC is fed into a flyback transformer which converts it into low voltage AC. The flyback transformer also isolates the chopped DC from the low voltage AC. This prevents the shock hazard of house line voltage getting into the output. Finally, this AC is converted into DC which is filtered to obtain smooth power free of interference, and this power is output through the USB jack. A feedback circuit measures the output voltage and sends a signal to the controller IC, which adjusts the switching frequency to obtain the desired voltage.
It is the knock-off counterfeit chargers that do the voltage drop with transformerless circuits using resisters, capacitors and diodes that are the problem. It is a circuit that is basically a voltage divider that uses a capacitor instead of a resistor to takes the 120 VAC from your wall and divides it down to whatever voltage you want. They may be cheap to build, but pose a shock hazard if a line voltage surge causes a critical capacitor to develop a short. Also, the wire that serves as the circuits ground reference is the same as your homes neutral line (in contrast with the hot line). Now imagine mistakenly putting the plug in backwards. Ground is hot, and although the device works just fine because AC is symmetric, it becomes an electrocution hazard if you can come in contact with ground in a wet bath tub.
Agree. But short from 110VAC side of power cube to wet plumbing as ground certainly could.
“Ground-fault interrupters in the bathroom. Lifesavers”
Must have been and old house.
5 volts are going into the phone, so that won’t do it. The charger is plugged into the wall and is carrying the usual 120 volts, so the CHARGER fell into the tub. How about some accuracy here?
Voltage tickles. Current kills.
Under the right (or wrong, depending on one’s point of view) circumstances, much less than 1 Amp can be deadly, and someone up thread stated their phone charger was rated for up to an amp.
Nonetheless, we need to keep reinforcing with the youngsters that electricity and water cannot be safely mixed.
Thanks for the info re: GFCIs.
But the crux: Why is it bad to plug a power strip into another power strip? I do that in my garage when I need a few extra feet of cord.
I think you nailed it. To get a burn mark it had to be 110V. The wall charger was not isolated. A non isolated charger is dangerous.
Phones are smarter than the people.
Even without a GFI, the plug in AC adapter puts out low voltage/low current DC to the phone. If the phone was immersed while plugged in, how could it NOT short out the converter or even blow the fuse/trip the breaker for the outlet? And how could it deliver a fatal AC charge?
There’s more to this than what is being reported. The 5V output from a cell phone charger is “floating”, in other words, not referenced to ground. No current would flow from either the positive or negative side of the 5V circuit to her or the water in the tub.
Either the charger was defective or she came into contact with the AC line.
“But now their mission is to make sure it doesnt happen again.
This is such a tragedy that doesnt need to happen to anyone else. And we want something good to come out of this as awareness of not using your cell phone in the bathroom as it is plugged in and charging,” O’Guinn said.”
You are correct. It is a parental thing. And now, as so very often happens...
The parents are on a “mission” to teach other parents how to save their children.... even though they weren’t aware enough to save their own child.
“It is the knock-off counterfeit chargers that do the voltage drop with transformerless circuits using resisters, capacitors and diodes that are the problem. It is a circuit that is basically a voltage divider that uses a capacitor instead of a resistor to takes the 120 VAC from your wall and divides it down to whatever voltage you want. They may be cheap to build, but pose a shock hazard if a line voltage surge causes a critical capacitor to develop a short.”
I don’t buy this part. It would not be cheaper to build, and it would have to be huge. At 60 HZ, it would take a 20uf capacitor to pass an amp of current. 22uf is the size of a run cap on a small blower motor, and there about $10 each.
Resistors would be more expensive and would have to dissipate about 100 watts or so.
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