On 31/01/2019 15:10, whisky-dave wrote:
On Thursday, 31 January 2019 11:44:36 UTC, Martin Brown wrote:
On 30/01/2019 13:39, whisky-dave wrote:
On Wednesday, 30 January 2019 04:16:40 UTC, Rod Speed wrote:
wrote in message
...
On Tuesday, 29 January 2019 17:09:04 UTC, Dave Plowman (News) wrote:
In article ,
R D S wrote:
And why do similar rated ones differ so much in bulk? Is this just a
build quality issue?

Older ones will have a transformer. Newer ones a SMPS - smaller and
lighter.

All wallwarts use a transformer.

Not all of them do. Some of the lower
power ones just use a capacitor dropper.

How do they work then ?

Did they not teach you the impedance of a capacitor then?

Well yes but it's really Reactance you're refering to isn't it.

And we donlt in the UK for wall marts use capacitors to drop the voltage.



It is a potential divider for AC implemented with capacitors rather than
resistors. It is the capacitive equivalent of an autotransformer.

except they aren't really used , it;s OK in theory for an idea capacitor but they don't exist in the real world.



Snag is that there is no isolation of the mains this way.

Another reason we donlt use them in the UK.

The "low
voltage" output can find itself at mains potential if the wrong
capacitor fails open circuit. Killed some Apple user in the bath.

https://www.telegraph.co.uk/news/201...g-iphone-bath/

I actually fail to see how he was killed by a genuine Apple charging
device - all the ones I have seen were properly engineered.

Not a very good report is it.
It shows the headphone to lightning adapter as the charger ?
It also says that the charger was in the bath which is a differnt type of accident, and what;'s this extention cord they are refering to ?


"We found an iPhone plugged into the extension cable and then the charger element in the bath," he explained."


How do you know what voltage they produce and how will it convert the AC to DC.

Electronic engineering and rather simple formulae.

Which only works in theory NOT in the real world unless you;re making cheap chinese chargers.
The forst enalrger timer I built from a magazine used a 10W 33K dropper resistor to power a 555.

I used to have a battery charger for NiCd button cells that consisted of
a resistor and a diode. In a ventilated plastic case with a little
carrier thing to insert the cell. (Used for a teeny Russian LW/MW
personal radio about 1"x3/4"x1/4" which used thin film integration and
six transistors.)

--
Max Demian