f



QI wireless charging??

I've been experimenting with wireless charging using receivers that
plug into the USB port like these:

http://www.ebay.com/itm/Universal-QI-Wireless-Charging-Receiver-Charger-Module-For-Micro-USB-Cell-Phone-/311711694882?var=&hash=item4893770022:m:mYzdYomY6gT4IsBfKhzpgpw

I no longer have to fiddle around in the dark trying to plug in the
charger without busting the connector.  Just throw it on the charger
and be done with it.

They work great with phones.

I tried 'em on small tablets.  Work for a while, but self-destruct.
The regulator chip melts the plastic and dies.  I haven't tried
heat sinking it.

The tablet wants 1.8A, but charges just fine from a wired charger
of lower rating.
The QI receiver is specified at 1A.

I thought I understood that the QI receiver and transmitter negotiated
the current so that neither would be damaged.  I'm wondering if changing
to a different receiver or transmitter would help?  And how do I determine
which is at fault?

Anybody got experience/advice on this issue?
Is there an affordable receiver that won't self-destruct on a higher-drain
tablet?


0
mike
12/20/2016 12:58:13 AM
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mike <ham789@netzero.net> wrote in news:o39vkq$gp4$1@dont-email.me:

> I've been experimenting with wireless charging using receivers that
> plug into the USB port like these:
> 
> http://www.ebay.com/itm/Universal-QI-Wireless-Charging-Receiver-Charger
> -Module-For-Micro-USB-Cell-Phone-/311711694882?var=&hash=item4893770022
> :m:mYzdYomY6gT4IsBfKhzpgpw 
> 
> I tried 'em on small tablets.  Work for a while, but self-destruct.
> The regulator chip melts the plastic and dies.  I haven't tried
> heat sinking it.
> 
> The tablet wants 1.8A, but charges just fine from a wired charger
> of lower rating.
> The QI receiver is specified at 1A.
> 
> Anybody got experience/advice on this issue?
> Is there an affordable receiver that won't self-destruct on a
> higher-drain tablet?
> 
> 
> 
I have been using this charger for my Nexus 7 2013 for almost a year now.

https://www.amazon.com/gp/product/B00Y839YMU/ref=oh_aui_detailpage_o01
_s00?ie=UTF8&psc=1

My tablet is rated for somewhere around an amp and a half, but charges 
just fine at one amp from this Anker QI charger. It actually seems to 
charge faster than when I plug in directly to my Anker 2A charger. The 
only drawback is that I can't use a case anymore because it is too thick 
and the charger and tablet don't see each other. Also, make sure you have 
your tablet's charging area squarely on the charger. Otherwise the light 
might indicate charging, but the full charge isn't getting through and 
you don't really get anywhere.
0
Tim
12/20/2016 1:22:38 AM
On 12/19/2016 5:22 PM, Tim wrote:
> mike <ham789@netzero.net> wrote in news:o39vkq$gp4$1@dont-email.me:
>
>> I've been experimenting with wireless charging using receivers that
>> plug into the USB port like these:
>>
>> http://www.ebay.com/itm/Universal-QI-Wireless-Charging-Receiver-Charger
>> -Module-For-Micro-USB-Cell-Phone-/311711694882?var=&hash=item4893770022
>> :m:mYzdYomY6gT4IsBfKhzpgpw
>>
>> I tried 'em on small tablets.  Work for a while, but self-destruct.
>> The regulator chip melts the plastic and dies.  I haven't tried
>> heat sinking it.
>>
>> The tablet wants 1.8A, but charges just fine from a wired charger
>> of lower rating.
>> The QI receiver is specified at 1A.
>>
>> Anybody got experience/advice on this issue?
>> Is there an affordable receiver that won't self-destruct on a
>> higher-drain tablet?
>>
>>
>>
> I have been using this charger for my Nexus 7 2013 for almost a year now.
>
> https://www.amazon.com/gp/product/B00Y839YMU/ref=oh_aui_detailpage_o01
> _s00?ie=UTF8&psc=1

My Qi transmitter looks exactly like that one, but I got it far cheaper
from China.  No idea whether it's the same inside.
I have several transmitters, but it's difficult to instrument
exactly what's going on. I've burned out three receivers so far.
I think I'll tap into the receiver ahead of the dead regulator
and plot the V-I curve for all the transmitters.

One of my tablets is a Nexus 7 2012.  It has no internal Qi receiver,
so I'm using the external USB one linked above.  The RECEIVER is the
part that is breaking.

>
> My tablet is rated for somewhere around an amp and a half, but charges
> just fine at one amp from this Anker QI charger. It actually seems to
> charge faster than when I plug in directly to my Anker 2A charger. The
> only drawback is that I can't use a case anymore because it is too thick
> and the charger and tablet don't see each other. Also, make sure you have
> your tablet's charging area squarely on the charger. Otherwise the light
> might indicate charging, but the full charge isn't getting through and
> you don't really get anywhere.
>

0
mike
12/20/2016 2:04:13 AM
mike <ham789@netzero.net> wrote:

> I've been experimenting with wireless charging using receivers that
> plug into the USB port like these:
> 
> http://www.ebay.com/itm/Universal-QI-Wireless-Charging-Receiver-Charger-Module-For-Micro-USB-Cell-Phone-/311711694882?var=&hash=item4893770022:m:mYzdYomY6gT4IsBfKhzpgpw

There are some that will connect the coil pack to an internal port.
Those are for smartphones that have the feature but wireless charging
was left off in a cheaper version of the product.

When you get the ones that have to connect to the outside USB port, you
have to make sure you get the one that has the correct orientation of
the USB connector.  You could end up getting one that, after bending up
and around, is reversed.  When bending up the flat cable, the narrow and
wide sides of the connector have to match up with the narrow and wide
sides of the port.

Something else to consider is that you never be able to use the phone's
USB port for anything else.  You won't be able to transfer files between
the phone and your computer.  You won't be able to use much faster
charging wired chargers.  You could leave a loop of the coil pack's
cable hanging outside the phone but that means it could get snapped and
rip the cable or damage the port.  Typically you connect the coil pack,
shove it inside the phone so its cable is snug, and snap on the back of
the phone.  You lose use of the USB port on the phone to have slow
wireless charging.

Oh, and that coil pack won't give you wireless charging.  You will still
have to go buy a Qi charger (~$40-$50).  That they list 2A is what the
charger eats, not what it supplies via inducation across air to the
phone.  See mention below on why you need to be careful what Qi charger
you buy.
 
> I no longer have to fiddle around in the dark trying to plug in the
> charger without busting the connector.  Just throw it on the charger
> and be done with it.

Be careful.  Some cordless chargers have only a single coil.  If you
don't properly align your smartphone atop the charger, the misalignment
generates heat and the smartphone could burn up.  Get the cordless
chargers that have 3 coils so placement can be much more sloppy.  Some
even include an indicator (visible and/or audible) to tell you when the
smartphone is properly aligned atop the cordless charger.

Induction charging is far less efficient than direct connects.  It will
take a lot longer to use a cordless charger than a corded one.  Plus
wiht a corded charger you may have the choice of plugging into a USB2
port (only 1/2 amp load), a USB3 port (2A load), or into an A/C adapter
(often 2A capacity but can be more although the phone will problem use
current limiting to protect the lithium battery).

Because the USB port on the phone gets used up just for the wireless
coil pack, and because charging is slow via wireless, I opted to skip
getting a Qi coil pack and Qi charger.  I want to charge my phone
anywhere with a highly portable USB cable (to a power pack or computer)
or even with the USB cable plus the small A/C-to-USB adapter (to use an
A/C outlet to charge).  I've got a couple power packs (small and big
capacity) because there are times when the phone is not just on but
active for long times, like when using GPS and mapping to tell me how to
get somewhere that is hundreds of miles away.  With Qi, I don't get
another charge until I got back home.  I suppose I could buy another Qi
charger to leave in my car, and another to leave at my workdesk.  The
convenience (well, no cord to phone but slow charging) would get quickly
get pricey.

As you have found out, the Qi coil packs are cheap.  A *good*, like
multiple coils, Qi charger is expensive.  Getting several of them to
have at common locations (home, work, car) will be expensive.  What are
you going to do when on vacation?  Haul one with you?
0
VanguardLH
12/20/2016 5:02:56 AM
VanguardLH <V@nguard.LH> wrote in news:ebrsc0F2850U1@mid.individual.net:

> Induction charging is far less efficient than direct connects.  It
> will take a lot longer to use a cordless charger than a corded one. 
> Plus wiht a corded charger you may have the choice of plugging into a
> USB2 port (only 1/2 amp load), a USB3 port (2A load), or into an A/C
> adapter (often 2A capacity but can be more although the phone will
> problem use current limiting to protect the lithium battery).
> 
> 
Actually, a true USB 3.0 port only provides 950mA, as opposed to the 500mA 
for USB 2. USB 3.1 does allow higher rates in some features, but those are 
very rarely implemented on a desktop or laptop computer. It is only with 
wall warts/car chargers/power banks that one can get more than .95A of 
charging current.
0
Tim
12/20/2016 8:17:06 AM
On 12/19/2016 9:02 PM, VanguardLH wrote:
> mike <ham789@netzero.net> wrote:
>
>> I've been experimenting with wireless charging using receivers that
>> plug into the USB port like these:
>>
>> http://www.ebay.com/itm/Universal-QI-Wireless-Charging-Receiver-Charger-Module-For-Micro-USB-Cell-Phone-/311711694882?var=&hash=item4893770022:m:mYzdYomY6gT4IsBfKhzpgpw
>
> There are some that will connect the coil pack to an internal port.
> Those are for smartphones that have the feature but wireless charging
> was left off in a cheaper version of the product.
>
> When you get the ones that have to connect to the outside USB port, you
> have to make sure you get the one that has the correct orientation of
> the USB connector.  You could end up getting one that, after bending up
> and around, is reversed.  When bending up the flat cable, the narrow and
> wide sides of the connector have to match up with the narrow and wide
> sides of the port.
>
> Something else to consider is that you never be able to use the phone's
> USB port for anything else.  You won't be able to transfer files between
> the phone and your computer.  You won't be able to use much faster
> charging wired chargers.  You could leave a loop of the coil pack's
> cable hanging outside the phone but that means it could get snapped and
> rip the cable or damage the port.  Typically you connect the coil pack,
> shove it inside the phone so its cable is snug, and snap on the back of
> the phone.  You lose use of the USB port on the phone to have slow
> wireless charging.
>
> Oh, and that coil pack won't give you wireless charging.  You will still
> have to go buy a Qi charger (~$40-$50).  That they list 2A is what the
> charger eats, not what it supplies via inducation across air to the
> phone.  See mention below on why you need to be careful what Qi charger
> you buy.
>
>> I no longer have to fiddle around in the dark trying to plug in the
>> charger without busting the connector.  Just throw it on the charger
>> and be done with it.
>
> Be careful.  Some cordless chargers have only a single coil.  If you
> don't properly align your smartphone atop the charger, the misalignment
> generates heat and the smartphone could burn up.  Get the cordless
> chargers that have 3 coils so placement can be much more sloppy.  Some
> even include an indicator (visible and/or audible) to tell you when the
> smartphone is properly aligned atop the cordless charger.
>
> Induction charging is far less efficient than direct connects.  It will
> take a lot longer to use a cordless charger than a corded one.  Plus
> wiht a corded charger you may have the choice of plugging into a USB2
> port (only 1/2 amp load), a USB3 port (2A load), or into an A/C adapter
> (often 2A capacity but can be more although the phone will problem use
> current limiting to protect the lithium battery).
>
> Because the USB port on the phone gets used up just for the wireless
> coil pack, and because charging is slow via wireless, I opted to skip
> getting a Qi coil pack and Qi charger.  I want to charge my phone
> anywhere with a highly portable USB cable (to a power pack or computer)
> or even with the USB cable plus the small A/C-to-USB adapter (to use an
> A/C outlet to charge).  I've got a couple power packs (small and big
> capacity) because there are times when the phone is not just on but
> active for long times, like when using GPS and mapping to tell me how to
> get somewhere that is hundreds of miles away.  With Qi, I don't get
> another charge until I got back home.  I suppose I could buy another Qi
> charger to leave in my car, and another to leave at my workdesk.  The
> convenience (well, no cord to phone but slow charging) would get quickly
> get pricey.
>
> As you have found out, the Qi coil packs are cheap.  A *good*, like
> multiple coils, Qi charger is expensive.  Getting several of them to
> have at common locations (home, work, car) will be expensive.  What are
> you going to do when on vacation?  Haul one with you?
>
Wow!
Looks like wireless charging is not for you.
It IS for me.  I'm WAY less demanding.
Just need to figger out why the receiver is melting on a tablet...
and a way to prevent it.
0
mike
12/20/2016 9:33:10 AM
On Mon, 19 Dec 2016 16:58:13 -0800, mike <ham789@netzero.net> wrote:

>I've been experimenting with wireless charging using receivers that
>plug into the USB port like these:
>
>http://www.ebay.com/itm/Universal-QI-Wireless-Charging-Receiver-Charger-Module-For-Micro-USB-Cell-Phone-/311711694882?var=&hash=item4893770022:m:mYzdYomY6gT4IsBfKhzpgpw
>
>They work great with phones.
>
>I tried 'em on small tablets.  Work for a while, but self-destruct.
>The regulator chip melts the plastic and dies.  I haven't tried
>heat sinking it.

So your phone draws less power when charging than the tablet and the
tablet manages to max out the receiver which gets hot when going at
maximum. So far no surprise.

>The QI receiver is specified at 1A.

Just to give you some comparison:

Qi-Backcover for Samsung Galaxy S4 is rated at 5V 650mA
Qi-Backcover for Samsung Galaxy S5 is rated at 5.3V 760mA
Qi-Backcover for Samsung Galaxy Note 4 is rated at 5V 800mA

You'll notice a (modest) increase over time but basically some no-name
and very cheap product does magically better than something that has
actually seen some egineering? Phoney! If the rating is actually true
it's likely out of Qi-Specifications and that's why it's overheating.

>Anybody got experience/advice on this issue?

As convenient as they may be those third-party pads are potentially
dangerous and I'd recommend to stop using them. 

There are micro-usb cables that not only have a printed mark on the
plug to show the correct orientation but also a phyiscal knob or bar
to indicate which side is up. With these correct orientation is
guaranteed even in total darkness.
0
Hubert
12/20/2016 5:21:50 PM
mike <ham789@netzero.net> wrote:

> VanguardLH wrote:
>
>> Be careful.  Some cordless chargers have only a single coil.  If you
>> don't properly align your smartphone atop the charger, the misalignment
>> generates heat and the smartphone could burn up.  Get the cordless
>> chargers that have 3 coils so placement can be much more sloppy.  Some
>> even include an indicator (visible and/or audible) to tell you when the
>> smartphone is properly aligned atop the cordless charger.
>
> Just need to figger out why the receiver is melting on a tablet...
> and a way to prevent it.

Misalignment (and using 3-coil chargers to reduce misalignment) was
already mentioned.  You need a better wireless charger base: 3 coils,
visible or audible indicator to notify when alignment is good.
0
VanguardLH
12/21/2016 12:23:58 AM
Tim <timothybil@yahoo.com> wrote:

> VanguardLH <V@nguard.LH> wrote in news:ebrsc0F2850U1@mid.individual.net:
> 
>> Induction charging is far less efficient than direct connects.  It
>> will take a lot longer to use a cordless charger than a corded one. 
>> Plus wiht a corded charger you may have the choice of plugging into a
>> USB2 port (only 1/2 amp load), a USB3 port (2A load), or into an A/C
>> adapter (often 2A capacity but can be more although the phone will
>> problem use current limiting to protect the lithium battery).
>> 
> Actually, a true USB 3.0 port only provides 950mA, as opposed to the 500mA 
> for USB 2. USB 3.1 does allow higher rates in some features, but those are 
> very rarely implemented on a desktop or laptop computer. It is only with 
> wall warts/car chargers/power banks that one can get more than .95A of 
> charging current.

Oops, you're right.  A/C chargers can (but not always) give the highest
charging capacity.  USB3 next.  USB 2 is low.  Wireless Qi charging is
worse.

With A/C charging, there is a transformer involved but its primary
windings are tightly bound to the secondary.  Distance is small.
However, the coils in the phone coil pack and those in the wireless
charger base are much farther apart.  Plus there is the problem of
misalignment which doesn't happen in a transformer.  Users are
accustomed to the A/C wart feeling warm and yet they think a less
efficient coupling between their phone and charger base will be cool (or
the same warmth) rather than a lot warmer.  If A/C chargers were just as
badly misaligned and distanced as for wireless phone charging, they
would be a lot warmer, too.  

Misalignment creates heat above that already inherent in using induction
in a transformer (of which the coil pack in the phone and charger base
make a transformer).  Adding pretty cases onto smartphones adds distance
for even less efficiency.

I'm not sure the coil packs the OP is using are the problem.  More
likely misalignment of coil pack (inside the phone) to the charger base
is causing all the heat that he remarks is burning up the coil packs.
When users put those inside the back cover of the phone, they are not
perfectly aligned or perpendicular to the sides of the phone.  Once
inside, the user won't know exactly where is the coil pack, especially
since it will be positioned on its backside atop the charger.

The wireless receiver (secondary coil inside the phone) has a PCB with
A/C to DC conversion and regulation.  Conversion generates heat, too.
Maybe the cheapy wireless coil packs don't convert efficiency (to reduce
heat) and regulate down to the required output DC voltage (also
generates heat) so they burn up.

As I understand, there can be communication through the transformer
setup back to the charger that somehow helps it determine best possible
(obviously not as best as in a transformer) orientation of the secondary
coil.  An inept charger could be responsible for not keeping the current
load in the secondary (coil pack inside the phone) at a safe level.
Since alignment and distance between coils (primary and secondary) and
even the angle between them can vary, I'm not sure how accurate the
charger can be in determining how to regulate the primary coil (in the
charger) so there isn't too much current going through the secondary
coil (in the phone).  

Are there any NFC-capable smartphones that don't also come with wireless
charging?  If so, I'm wondering if the coil in the receiver pack (inside
the phone) for wireless charging might interfere with the NFC
transceiver.  With phones that are equipped to have a wireless receiver
added (they have internal contacts) and if you buy the one for the phone
then it is probably right-sized to not interfer with NFC.  The ones you
slide in anywhere under the back cover and stick out with a flat cable
to plug into the outside USB port could be anywhere inside the phone so
they might interfere with NFC.

0
VanguardLH
12/21/2016 1:09:07 AM
Worth noting that many users will be considering Wireless charging 
for the same reason as me.
The Tablet/phone is getting old & the USB corded socket
is worn/dirty / loose.
If that USB socket fails the device can't be charged at all.

My Nexus 7  (2013) charges at best 15% per hour & usually around 10% hour .
A full 100% takes typically 8 to 10 hours.
Not convenient !

Wireless looks like a solution even if it is slower than
a actual (not very efficient) corded connection.

(\__/)
(='.'=) This is Bunny. Copy and paste Bunny into your
(")_(") signature to help him gain world domination.
0
Trimble
12/21/2016 2:04:15 AM
On 12/20/2016 4:23 PM, VanguardLH wrote:
> mike <ham789@netzero.net> wrote:
>
>> VanguardLH wrote:
>>
>>> Be careful.  Some cordless chargers have only a single coil.  If you
>>> don't properly align your smartphone atop the charger, the misalignment
>>> generates heat and the smartphone could burn up.  Get the cordless
>>> chargers that have 3 coils so placement can be much more sloppy.  Some
>>> even include an indicator (visible and/or audible) to tell you when the
>>> smartphone is properly aligned atop the cordless charger.
>>
>> Just need to figger out why the receiver is melting on a tablet...
>> and a way to prevent it.
>
> Misalignment (and using 3-coil chargers to reduce misalignment) was
> already mentioned.  You need a better wireless charger base: 3 coils,
> visible or audible indicator to notify when alignment is good.
>
Misalignment is unlikely to cause the buck regulator chip to overheat.

Can't argue with your suggestions, but don't think that's the issue here.

0
mike
12/21/2016 10:56:13 AM
Per Hubert H.P. Wachter:
>There are micro-usb cables that not only have a printed mark on the
>plug to show the correct orientation but also a phyiscal knob or bar
>to indicate which side is up. With these correct orientation is
>guaranteed even in total darkness.

On all my micro-usb cables I put a drop of nail polish (black for the
white cables and white for black cables) on the plug.

Easy to ID visually, and I can feel the little lump in the dark.
-- 
Pete Cresswell
0
PeteCresswell
12/21/2016 2:52:07 PM
In article <ebrsc0F2850U1@mid.individual.net>, VanguardLH <V@nguard.LH>
wrote:

> Induction charging is far less efficient than direct connects.  It will
> take a lot longer to use a cordless charger than a corded one. 

my nexus 5 charges in approximately the same time either way. the
difference is a few minutes longer (out of an hour or whatever it is).
0
nospam
12/21/2016 11:03:53 PM
mike <ham789@netzero.net> wrote:

> VanguardLH wrote:
>
>> Misalignment (and using 3-coil chargers to reduce misalignment) was
>> already mentioned.  You need a better wireless charger base: 3 coils,
>> visible or audible indicator to notify when alignment is good.
>
> Misalignment is unlikely to cause the buck regulator chip to overheat.
> 
> Can't argue with your suggestions, but don't think that's the issue here.

Misalignment = less efficiency.
Less efficiency = more power loss = more heat.

http://www.allaboutcircuits.com/technical-articles/an-overview-of-wireless-charging/
https://www.wirelesspowerconsortium.com/technology/magnetic-resonance-and-magnetic-induction-making-the-right-choice-for-your-application.html

Even if you want to argue the heat is produced only in the charger base,
well, on what is the phone resting?  I'm not sure about the receiver's
heat damaging the phone but heat is the bane of lithium batteries.

Oh, by the way, I include distancing as part of misalignment, not just
off-center coil positioning.  Putting the phone atop a block eraser is
also misalignment since the phone is too far away.  Thick cases to make
the phone pretty cause increased power loss.  Obviously metallic phone
cases are not only to cause a problem with induction charging but also
with the radios within the smartphone in attenuating signal strength.
0
VanguardLH
12/22/2016 1:26:04 AM
On 12/21/2016 5:26 PM, VanguardLH wrote:
> mike <ham789@netzero.net> wrote:
>
>> VanguardLH wrote:
>>
>>> Misalignment (and using 3-coil chargers to reduce misalignment) was
>>> already mentioned.  You need a better wireless charger base: 3 coils,
>>> visible or audible indicator to notify when alignment is good.
>>
>> Misalignment is unlikely to cause the buck regulator chip to overheat.
>>
>> Can't argue with your suggestions, but don't think that's the issue here.
>
> Misalignment = less efficiency.
> Less efficiency = more power loss = more heat.
>
> http://www.allaboutcircuits.com/technical-articles/an-overview-of-wireless-charging/
> https://www.wirelesspowerconsortium.com/technology/magnetic-resonance-and-magnetic-induction-making-the-right-choice-for-your-application.html
>
> Even if you want to argue the heat is produced only in the charger base,
> well, on what is the phone resting?  I'm not sure about the receiver's
> heat damaging the phone but heat is the bane of lithium batteries.
>
> Oh, by the way, I include distancing as part of misalignment, not just
> off-center coil positioning.  Putting the phone atop a block eraser is
> also misalignment since the phone is too far away.  Thick cases to make
> the phone pretty cause increased power loss.  Obviously metallic phone
> cases are not only to cause a problem with induction charging but also
> with the radios within the smartphone in attenuating signal strength.
>

I made one argument.  The secondary regulator buck converter chip melted
its way thru the plastic and failed.  That's how I know it was too hot.

I don't pretend to understand the process, but I believe that there
are two parts.  The inductive coupler produces a voltage.  There's some
negotiation taking place that changes the power produced by the transmitter
to achieve some coarse regulation in the output voltage of the first
stage in the receiver.
That voltage is applied to a buck converter that produces regulated
5V to the device being charged.

If I look at the thermal image of the receiver, the coil is not getting
very hot.  The buck converter is getting very hot.

I expect there is some coarseness in the power control in the transmitter,
but in general, bad coupling should REDUCE the output voltage of the first
stage until it can no longer supply the second stage and disconnect, or 
whatever algorithm they use.
The spec on the buck converter chip shows that efficiency increases as
the input voltage reduces.

If the transmitter and coil are getting hot, it's not showing up on the
thermal image.  The thermal image does show that the buck converter chip
is getting hot.

Despite your insistence, my experiments convince me that you are drawing 
the wrong conclusion...in this case.
Yes, any heat generated anywhere is probably less than ideal.
Inability to transmit  power due to bad
coupling does not have to result in huge heat generation in the second stage
buck converter chip.



0
mike
12/22/2016 7:43:37 AM
Reply: