Hi Jon,
Thank you very much for the detailed explanation on USB power supplies.
I now that I should have paired the DEVICE requirements with the USB POWER
SUPPLY capabilities:
DEVICE = Blackberry 8700 SUPPLY = TCPRIM2ULSSN 5.0vdc 750mA
DEVICE = Motorola V195 SUPPLY = PSM5037B 5.9vdc 375mA
DEVICE = Motorola RAZR SUPPLY = DCH3-05US-0300 5.0vdc 550mA
DEVICE = Motorola Earbud SUPPLY = FMP5185B 5.2vdc 450mA
From the discussion, can I "assume" if I hook the Motorola V195's USB
power
supply (5.9vdc 375mA) to the Blackberry 8700 device, that the Blackberry
will be getting more voltage than it 'expected' and that the current
delivered will be much less than expected (even more so due to the higher
voltage than expected)?
yes. Using the 195 is not a good idea. It has the lowest max current rating
and to high of a voltage.
Note though that these are MAX current safety ratings. They are the maximum
possible current that the device will draw with some headroom for safety at
the specified voltage. So in reality your Blackberry might only use 100mA
on avg. For example, I have some security cameras that use 80mA at 8V in
daytime but at night use 160mA because it switches to IR. Here I would need
a power supply that will deliver atleast 200mA(but at ~8V). Well, that is
unless I knew that the camera would not be ran at night and there would be
no way the "night vision" would be used(like if I disabled the photo sensor
to make sure).
This implies that USB chargers are NOT interchangable!
(The T-Mobile store clerks just might have been right.)
well, not all power supplies are interchangble. This is why you see so many
with different sizes. Some are very small because they do not have to supply
a large current to the device they were intended to use. If you hook them up
to another device that would use the same voltage but draw more current then
it will burn up the power supply(and possibly ruin the device).
But, what irks me is they all have the SAME CONNECTIONS!
They all "LOOK" the same to me!
lol. Yes. It can be annoying. My father has about 50 of these wall warts for
all his junk and there are about 4 different connectors. Some are very odd
while all the others usually use that "standard" jack that you always
see(not sure what the name of it is).
Does EVERYONE label all their USB chargers so they don't mix them up?
Or am I missing something fundamental here.
If it says it's a USB charger, but that we can't use them interchangably,
then are they REALLY USB power supplies?
Well, all power adapators should be labeled with the power(voltage and
current) that they can supply. The device should also say which one it
uses. I'm sure that in some cases they do not say this on the device itself
probably because the manufacturer wants increase the likelyhood of the user
ruining the device so they will spend more money on it to get it repaired or
buy a new one.
Ultimately though these are just power supplies/adaptors and do not really
have anything to do with USB. USB is a standard that devices how "USB
Devices" will behave and communicate to other USB compatible devices.
The odd thing is that USB devices are defined to use 5.0V. This is strange
because
DEVICE = Motorola V195 SUPPLY = PSM5037B 5.9vdc 375mA
Is using 5.9V which is almost a full volt over. There could be many reasons
for this. Maybe the power supply is wrong. Maybe the device does not conform
to the USB spec. Or maybe the device can tolerate a large voltage
swing(maybe it uses 5.0V just fine). It could also be that the device uses
the 5.0V on a proper USB connection but not in the power supply part. i.e.,
there could be a difference between the USB port and the power port. Those
extra 0.9V could be from some extra safety feature the device uses on the
power port.
I'm not quite sure the reasons though.
I'm still confused on the fact that the charger advertises it is USB but
it's not USB if it doesn't fit all USB devices.
Ok, suppose you go into a store and you need a "USB" charger replacement
because you lost yours. You find many different adaptors saying they are
USB chargers. In fact there is no such thing. They are all just power
supplies/adapators. Its possible some manufacturers created a bunch of
power supplies for some device and then decided to sale them on the side and
call them USB Chargers because they were ~5.0VDC.
What I'm trying to get at is that USB does not device power supplies or
chargers but only states that USB devices should use 5.0VDC. Just like all
computers use a power supply that supplies 12VDC and 5VDC. If you have a
USB device then it *should* use 5.0VDC(but I suppose there are times when it
can't or won't) but there are many non-USB devices that also use 5.0VDC.
You also have the issue of current rating. Even at the same voltages you
have to make sure the supply can give enough current. All power constant
voltage power supplies have this issue because it is one of resource. The
larger the max current rating the more expensive the supply(in general).
This is why sometimes you'll find these little crap power adapators with
100mA. They are practically useless to use for most devices because most
devices use more than 100mA.
Can someone clear up the USB part of the confusion here?
I don't think I can but only say that sometimes a manufacturer has its
reasons. Sometimes they might change the power connector to be unique so
only the power supply they make will work for it. I assume they have there
reasons. Ultimately it would be easier for them to have one type of
connector for each voltage rating and have all power supplies have a max
current rating of 1A. This way you probably need at most 10 power supplies.
One for 1V, one for 2V, etc... All 1V power supplies would work with all
devices that ran at 1V(except those that used over 1A). Ofcourse if you had
more than 1 device at the same voltage rating to use at the same time you'd
need another power supply.
Essentially power supplies with the same connectors and same voltage are
interchangble if they can supply the maximum current the device uses.
Another thing to point out is that "chargers" are usually not the same as
adapatiors/supplies. Chargers usually have constant current and somewhat
different beasts. Constant voltage sources will keep the voltage constant
and allow for the change the current while constant current sources will
keep the current constant and allow for the change of voltage. Both cannot
change the part that varies from -infinity to infinity and different
adapators will have different ranges(usually 0 to max_cur for a voltage
source).
Anyways, If your trying to find one adapator for all the devices then it
seems your going to have a tough problem. Motorola V195 is just to far out.
You can see if it will work with a 5.0V source though. If it does then it
might be ok(although you might have wierd issues). For all the others you
can get a 5.0VDC@1A and it will work for all of them(well the 5.2V is a
little iffy but it should be ok). The issue then becomes one of connector
type. A all of them do not use the same connector type then you'll probably
want to by a multi-connector adapator.
Now if you know about electronics you could design a variable voltage source
where you could select the voltage you wanted almost exactly. I have no
idea if they sale these things to the consumer though but they are nice to
have. I assume they do not because it requires some knowledge about how
power works(The stuff I said about basically) and one has to make sure they
do not use the wrong settings or they could ruin the device.
Ultimately it would be nice is manufacturers would get there stuff together
and all use compatible power supplies for the same voltage. Here the issue
is one of cost though and a manufacturer is not going to sink in the extra
money on a power supply that is only "half" used.
Jon