[SML] picky charger

[Charlie Richmond]

Sounds like a perfect thing for Big Clive to investigate!!
https://www.youtube.com/user/bigclivedotcom

C-)

On Sun, Jun 24, 2018 at 9:22 AM, Jerry Durand via Stagecraft <
stagecraft at theatrical.net> wrote:

> The charger is two wire double insulated, but note it's a wireless one.
> It charges the device when it's just close to it.
>
> The inverter output isn't floating, but I'm pretty sure the way it
> generates a pure sine wave is the key.  In making a pure sine wave the
> first thought that would come to mind is tying the neutral to ground in the
> inverter and then just making a sine on the "hot", but that requires it to
> have twice the internal DC voltage to go from positive peak to negative
> peak.
>
> So what this does is the "neutral" output is a pure square wave while the
> "hot" output is two half sine waves.  When the "neutral" is at ground, the
> "hot" makes a half wave from ground up to peak, then back to ground.  When
> it gets back to ground, the "neutral" and "hot" are switched together to
> peak voltage, then the "hot" makes an inverted wave starting from the peak
> voltage, going down to ground at what would be the - peak, then back up to
> peak voltage.  Both lines are then switched together back to ground to
> start everything over again.
>
> From the point of view of any modern device (pretty much everything is
> agnostic about which wire is "neutral" and which is "hot") this works great.
>
> But, back to the wireless charger, this would be putting a mains frequency
> (50/60Hz) bias into the air-coupled signal to the device to be charged.  I
> suspect this either prevents the charger from detecting the presence of a
> device to be charged or the device to be charged from realizing it's within
> range of the charger.
>
> Remember when battery chargers were a transformer, a full wave rectifier
> if you were lucky, otherwise a single selenium rectifier, and that was
> about it?
>
> On 06/24/2018 04:47 AM, Dan Sheehan via Stagecraft wrote:
>
> 1) Is perhaps the charger miswired so it uses hot-to-ground instead of
> hot-to-neutral ?
>     You could check for this by making an adaptor with neutral opened.
>     If the charger works on this, it's wrong.
>
> 2) Inverter output is just floating ?
>    That's perhaps a no-no, unless it's *specified* to be a ground isolator.
>    Should be OK, and desirable, to tie the inverter output  neutral to
> ground.
>
> 3) I've seen flourescent light fixtures (the 4-foot-long tube "shop light"
> kind)
>    not start if the metal case is not grounded, or in at least one case,
>   not start if the sheet metal cover is not present;
>    touch the glass with your hand, and it lights up then runs find.
>   Apparently it requires capacitive coupling from the tube to ground to
> start.
>
>
> On Sun, Jun 24, 2018 at 1:48 AM, Me via Stagecraft <
> stagecraft at theatrical.net> wrote:
>
>> I just had a wireless charger refuse to work on a pure sine wave
>> inverter.  I tried it on a wall outlet, works fine.  Tried again on the
>> inverter, no work.
>>
>> I checked the inverter output with a 'scope in differential mode, looked
>> close to perfect.  So...???
>>
>> Finally figured out the inverter isn't referenced to ground like the
>> mains are.  Nothing cares except this one charger.  Must be a marginal
>> design in the charger and the lack of a ground reference kills the function.
>>
>> Every day is a surprise!
>>
>> --
>> Jerry Durand, Durand Interstellar, Inc.
>> www.DurandInterstellar.com
>> tel: +1 408 356-3886
>> @DurandInterstel
>>
>> ____________________________________________________________
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>>
>
>
>
> --
> ...Dan Sheehan
> Fixer of things that break
> TD Walpole (MA) Footlighters
>
>
>
> ____________________________________________________________
> For list information see <http://stagecraft.theprices.net/> <http://stagecraft.theprices.net/>
> Stagecraft mailing listStagecraft at theatrical.nethttp://theatrical.net/mailman/listinfo/stagecraft_theatrical.net
>
>
> --
> Jerry Durand, Durand Interstellar, Inc.www.DurandInterstellar.com
> tel: +1 408 356-3886
> @DurandInterstel
>
>
>
> ____________________________________________________________
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> Stagecraft mailing list
> Stagecraft at theatrical.net
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>
>


-- 
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