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From: Jon Slaughter on 28 Dec 2006 23:35

"Emily" <emilymoberg(a)hotmail.com> wrote in message
news:spnts0u0xuzp$.l5ddai2xzpbc.dlg(a)40tude.net...
> Is it true that one MUST use ONLY the EXACT USB charger that comes with
> their cell phone or digital camera?
>
> Are USB chargers really not interchangable?
>
> The T-Mobile store told me I could only use their T-Mobile charger for my
> new USB based cellphone. After showing me the charger for the Motorola
> V195
> which is 5.9 volts 375ma, they then opened a desk drawer and handed me
> three melted USB chargers from blackberrys & digital cameras, one at 5.0
> volts, 750ma; another at 5.0 volts, 550 ma, and yet another at 5.2 volts
> 450 ma.
>
> Can we swap these supposedly USB chargers or not?
> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
> - Motorola PSM5037B 5.9vdc 375mA
> - Motorola DCH3-05US-0300 5.0vdc 550mA
> - Motorola FMP5185B 5.2vdc 450mA
>
> Why is Blackberry USB different than Motorola USB which is different in
> and
> of itself? Can we swap these USB chargers or must we stick to the charger
> that came with the device?


The current rating on a voltage source is the maximum amount that the power
source can deliver without exceeding its saftey rating.

What this means is that if you are using some device that has a power supply
with a current rating of 500mA then its best not to use a different power
supply(at the same votlage rating) with a lower max current rating. i.e.,
anything < 500mA. Now ofcourse you might be able to get away with it but if
it burns down your house then its your fault.

A device will only pull the amount of current that it uses(assuming it is a
voltage controlled device) and this is true regardless of the current
rating(hence the saftey issues I discussed above). If a device
says(sometimes they don't) it uses 500mA then it uses 500mA. Maybe it
doesn't use 500mA all the time but the engineers have put that rating there
for a reason. Using any power supply with the right voltage and a current
rating of anything more than what the device uses is ok because the device
will only pull the current it uses.

Now, about the voltage rating: The voltage rating does not have to be exact
and different devices can tolerate different voltage ratings. The problem
usually is one of current. By increasing the voltage, say, you increase the
current the device uses and then you have changed the parameters that the
device was created with.

i.e., suppose the device was created to work with 5VDC(a)1A. Now suppose you
use a power supply that is 6VDC. The device will not draw 1A but more than
one because of ohms law. It might draw so much more current that the
components will overheat or some other problems could happen. Not all
constant voltage power sources are equal... The voltage are not really
constant but the devices are usually designed to tolerate a small deviation.

So it may or may not be ok to use a different power source rated at a higher
voltage. Usually you can get away with using a lower voltage rating but when
you do this you decrease the current drawn by the device. It might not be
enough current to actually run the device. Having more than 1V over the
voltage rating is asking for trouble for most devices and even 1/2 a volt
might not be wise if you care about the device.


So, if you understand all that then your question is pretty trivial with the
answer "It depends".

> Can we swap these supposedly USB chargers or not?
> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
> - Motorola PSM5037B 5.9vdc 375mA
> - Motorola DCH3-05US-0300 5.0vdc 550mA
> - Motorola FMP5185B 5.2vdc 450mA

Each of these power supplies are designed for different device requirements.
They do this mainly because its cheaper.

you could get away with just one voltage source for 3 of the above:

> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
> - Motorola DCH3-05US-0300 5.0vdc 550mA
> - Motorola FMP5185B 5.2vdc 450mA

All could use a power supply of 5VDC(a)1A. This 1A rating gives enough current
to any of the devices here and the 5V should work with the FMP5185B. 0.2V
might be to much though and cause some issues.

> - Motorola PSM5037B 5.9vdc 375mA

This is basically a 6V device. I doubt the 0.1V matters to much but it
could. Usually devices are not designed to be that tolerant because most
components are not very precise. You might even be able to get this thing to
work off a 5VDC source but I'm not sure. It usually won't hurt to try as
long as it can supply the maximum rated current.

i.e. for the PSM5037B you could try a 5VDC(a)375mA and see if the device
works. Ofcourse you could try anything above 375mA and it could work(even
slightly lower since we lowered the voltage). At most you will probably fry
your power supply(but this could fry the device in some cases).


Ok, now for the practical side. Not all power sources are created equal.
Even two power sources at the same voltage and max current ratings can be
completely different. There are many types of methods of supplying power.
Usually your typical "wall wart" is just a piece of junk with nothing
special in it. If, say, you pull to much current from it then it can melt
but in the process increase the voltage which will cause more current to be
pulled with could fry your device. (remember, increasing the voltage on the
power supply increases the actuall current used by the device which could go
over the maximum current that the power supply can safely supply.)

If you have a need for many different power supplies then you might want to
get one with selectable voltages. Here though you will need to make sure you
don't hook any devices up that would draw more current than the power supply
can give and that you always select the right voltage and polarity that the
device needs.

> Can we swap these supposedly USB chargers or not?
> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
> - Motorola PSM5037B 5.9vdc 375mA
> - Motorola DCH3-05US-0300 5.0vdc 550mA
> - Motorola FMP5185B 5.2vdc 450mA
>
> Why is Blackberry USB different than Motorola USB which is different in
> and
> of itself? Can we swap these USB chargers or must we stick to the charger
> that came with the device?


Now heres the exact answer why these are different:.

The Blackberry draws a max of 750mA from its supply. If you use any of the
other supplies they will burn out because they cannot supply the 750mA.
(they actually will try but burn out because it would get really hot). Using
the PSM5037 on the Blackberry would be even worse than using the DCH
beacause the increase in voltage would increase the current used by the
Blackberry and surely draw to much current.

The same idea applies to the others. The TCPRIM could be used for the DCH3
and the FMP5185(probably) because it has the right voltage and gives much
more current than they need.


Whats would be really bad is to use say, a 10VDC(a)10A power supply on all the
devices. Here the devices would surely be destoryed and not the power
supply.

The reason is that the extra voltage would cause the device to consume more
current which would cause it to get hotter and most likely hotter than it
was designed for. Since it uses more current and because most lilely the
power supply can supply that current(since it can do 10A) it will not be
destroyed first and hence the device will eventually overheat and fail.
Specially since most cheap power supplies do not have very good safety
precautions along with devices not having fuses and such(I'm sure they do
this so the device will be ruined if used wrong and would need to be
replaced).

So while its ok to use a larger maximum current rating you have to make sure
the voltage rating is correct too so you can't make the device pull any more
current than it was designed for. e.g., a device that uses 5VDC and 500mA
will "always" use a *maximum* of 500mA at 5VDC and never any more(with
normal conditions). If you force it to use 7VDC then you also force it to
use more current... maybe 750mA. The device was not designed to use this
amount and something will fail(either the powersupply or the device).



Hope this helps,
Jon


From: Emily on 29 Dec 2006 02:53
On Fri, 29 Dec 2006 04:35:42 GMT, Jon Slaughter wrote:

> "Emily" <emilymoberg(a)hotmail.com> wrote in message
> news:spnts0u0xuzp$.l5ddai2xzpbc.dlg(a)40tude.net...
>> Is it true that one MUST use ONLY the EXACT USB charger that comes with
>> their cell phone or digital camera?
>>
>> Are USB chargers really not interchangable?
>>
>> The T-Mobile store told me I could only use their T-Mobile charger for my
>> new USB based cellphone. After showing me the charger for the Motorola
>> V195
>> which is 5.9 volts 375ma, they then opened a desk drawer and handed me
>> three melted USB chargers from blackberrys & digital cameras, one at 5.0
>> volts, 750ma; another at 5.0 volts, 550 ma, and yet another at 5.2 volts
>> 450 ma.
>>
>> Can we swap these supposedly USB chargers or not?
>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>> - Motorola PSM5037B 5.9vdc 375mA
>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>> - Motorola FMP5185B 5.2vdc 450mA
>>
>> Why is Blackberry USB different than Motorola USB which is different in
>> and
>> of itself? Can we swap these USB chargers or must we stick to the charger
>> that came with the device?
>
>
> The current rating on a voltage source is the maximum amount that the power
> source can deliver without exceeding its saftey rating.
>
> What this means is that if you are using some device that has a power supply
> with a current rating of 500mA then its best not to use a different power
> supply(at the same votlage rating) with a lower max current rating. i.e.,
> anything < 500mA. Now ofcourse you might be able to get away with it but if
> it burns down your house then its your fault.
>
> A device will only pull the amount of current that it uses(assuming it is a
> voltage controlled device) and this is true regardless of the current
> rating(hence the saftey issues I discussed above). If a device
> says(sometimes they don't) it uses 500mA then it uses 500mA. Maybe it
> doesn't use 500mA all the time but the engineers have put that rating there
> for a reason. Using any power supply with the right voltage and a current
> rating of anything more than what the device uses is ok because the device
> will only pull the current it uses.
>
> Now, about the voltage rating: The voltage rating does not have to be exact
> and different devices can tolerate different voltage ratings. The problem
> usually is one of current. By increasing the voltage, say, you increase the
> current the device uses and then you have changed the parameters that the
> device was created with.
>
> i.e., suppose the device was created to work with 5VDC(a)1A. Now suppose you
> use a power supply that is 6VDC. The device will not draw 1A but more than
> one because of ohms law. It might draw so much more current that the
> components will overheat or some other problems could happen. Not all
> constant voltage power sources are equal... The voltage are not really
> constant but the devices are usually designed to tolerate a small deviation.
>
> So it may or may not be ok to use a different power source rated at a higher
> voltage. Usually you can get away with using a lower voltage rating but when
> you do this you decrease the current drawn by the device. It might not be
> enough current to actually run the device. Having more than 1V over the
> voltage rating is asking for trouble for most devices and even 1/2 a volt
> might not be wise if you care about the device.
>
>
> So, if you understand all that then your question is pretty trivial with the
> answer "It depends".
>
>> Can we swap these supposedly USB chargers or not?
>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>> - Motorola PSM5037B 5.9vdc 375mA
>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>> - Motorola FMP5185B 5.2vdc 450mA
>
> Each of these power supplies are designed for different device requirements.
> They do this mainly because its cheaper.
>
> you could get away with just one voltage source for 3 of the above:
>
>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>> - Motorola FMP5185B 5.2vdc 450mA
>
> All could use a power supply of 5VDC(a)1A. This 1A rating gives enough current
> to any of the devices here and the 5V should work with the FMP5185B. 0.2V
> might be to much though and cause some issues.
>
>> - Motorola PSM5037B 5.9vdc 375mA
>
> This is basically a 6V device. I doubt the 0.1V matters to much but it
> could. Usually devices are not designed to be that tolerant because most
> components are not very precise. You might even be able to get this thing to
> work off a 5VDC source but I'm not sure. It usually won't hurt to try as
> long as it can supply the maximum rated current.
>
> i.e. for the PSM5037B you could try a 5VDC(a)375mA and see if the device
> works. Ofcourse you could try anything above 375mA and it could work(even
> slightly lower since we lowered the voltage). At most you will probably fry
> your power supply(but this could fry the device in some cases).
>
>
> Ok, now for the practical side. Not all power sources are created equal.
> Even two power sources at the same voltage and max current ratings can be
> completely different. There are many types of methods of supplying power.
> Usually your typical "wall wart" is just a piece of junk with nothing
> special in it. If, say, you pull to much current from it then it can melt
> but in the process increase the voltage which will cause more current to be
> pulled with could fry your device. (remember, increasing the voltage on the
> power supply increases the actuall current used by the device which could go
> over the maximum current that the power supply can safely supply.)
>
> If you have a need for many different power supplies then you might want to
> get one with selectable voltages. Here though you will need to make sure you
> don't hook any devices up that would draw more current than the power supply
> can give and that you always select the right voltage and polarity that the
> device needs.
>
>> Can we swap these supposedly USB chargers or not?
>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>> - Motorola PSM5037B 5.9vdc 375mA
>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>> - Motorola FMP5185B 5.2vdc 450mA
>>
>> Why is Blackberry USB different than Motorola USB which is different in
>> and
>> of itself? Can we swap these USB chargers or must we stick to the charger
>> that came with the device?
>
>
> Now heres the exact answer why these are different:.
>
> The Blackberry draws a max of 750mA from its supply. If you use any of the
> other supplies they will burn out because they cannot supply the 750mA.
> (they actually will try but burn out because it would get really hot). Using
> the PSM5037 on the Blackberry would be even worse than using the DCH
> beacause the increase in voltage would increase the current used by the
> Blackberry and surely draw to much current.
>
> The same idea applies to the others. The TCPRIM could be used for the DCH3
> and the FMP5185(probably) because it has the right voltage and gives much
> more current than they need.
>
>
> Whats would be really bad is to use say, a 10VDC(a)10A power supply on all the
> devices. Here the devices would surely be destoryed and not the power
> supply.
>
> The reason is that the extra voltage would cause the device to consume more
> current which would cause it to get hotter and most likely hotter than it
> was designed for. Since it uses more current and because most lilely the
> power supply can supply that current(since it can do 10A) it will not be
> destroyed first and hence the device will eventually overheat and fail.
> Specially since most cheap power supplies do not have very good safety
> precautions along with devices not having fuses and such(I'm sure they do
> this so the device will be ruined if used wrong and would need to be
> replaced).
>
> So while its ok to use a larger maximum current rating you have to make sure
> the voltage rating is correct too so you can't make the device pull any more
> current than it was designed for. e.g., a device that uses 5VDC and 500mA
> will "always" use a *maximum* of 500mA at 5VDC and never any more(with
> normal conditions). If you force it to use 7VDC then you also force it to
> use more current... maybe 750mA. The device was not designed to use this
> amount and something will fail(either the powersupply or the device).
>
>
>
> Hope this helps,
> Jon

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)?

This implies that USB chargers are NOT interchangable!
(The T-Mobile store clerks just might have been right.)

But, what irks me is they all have the SAME CONNECTIONS!
They all "LOOK" the same to me!

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?

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.

Can someone clear up the USB part of the confusion here?
Emily
From: Cgiorgio on 29 Dec 2006 03:45
USB or Universal Serial Bus is a standard for high speed serial data
transfer from a computer to a peripheral and vice versa. All your devices
can be connected to a computer using a USB data cable. If hooked up to a
computer, the USB cable carries 5.0 Volts DC on its power supply pins, no
USB device can suffer any damage from this voltage. In order to save the
space for a dedicated power supply jack, many portable devices now use their
mini-USB jack for charging internal batteries. In the case of Lithium based
chemistry the battery needs a precisely limited end of charge voltage
(nominal 3.6 Volt Li-Ion cells usually need 4.20 Volts). The charging
circuit is inside the portable device, but a DC power source is needed to
feed it. What is called a charger is in these cases really a DC power supply
or AC adaptor. You can find three different types of AC adaptors: The most
primitive type is relatively heavy and for a specific input voltage, it
contains an isolating transformer, a rectifier and most of the time a
capacitor to reduce AC ripple. A bit more complex are AC adaptors with a
stabilized DC output voltage that contain an electronic circuit that
stabilizes the output voltage as long as the load is within limits.
Excess-voltage is converted into heat by a linear regulator.

The third type is the universal input voltage / worldwide or switching power
supply. They are usually lighter, convert the 50 or 60 Hz AC voltage to DC
and then convert that electronically to high frequency AC which requires a
much smaller and lighter transformer. They vary the AC input to the little
transformer to compensate for deviations in the output voltage. All AC
adaptors that carry the UL sign have to include some means of overload
protection. Some adaptors will fail permanently when that means has tripped,
others will reset once input power or overload is removed.

Some AC adaptors may deliver a slightly higher DC voltage than the nominal
5.0 Volts to achieve a higher initial charge rate for the battery, but 5.0
Volts is safe with any USB interface. As mentioned before in this thread, it
is generally safe to use a power supply with a higher current rating, but
not with a much higher output voltage.

"Emily" <emilymoberg(a)hotmail.com> schrieb im Newsbeitrag
news:13pp30zu7ndor.19v8setskzqwm$.dlg(a)40tude.net...
> On Fri, 29 Dec 2006 04:35:42 GMT, Jon Slaughter wrote:
>
>> "Emily" <emilymoberg(a)hotmail.com> wrote in message
>> news:spnts0u0xuzp$.l5ddai2xzpbc.dlg(a)40tude.net...
>>> Is it true that one MUST use ONLY the EXACT USB charger that comes with
>>> their cell phone or digital camera?
>>>
>>> Are USB chargers really not interchangable?
>>>
>>> The T-Mobile store told me I could only use their T-Mobile charger for
>>> my
>>> new USB based cellphone. After showing me the charger for the Motorola
>>> V195
>>> which is 5.9 volts 375ma, they then opened a desk drawer and handed me
>>> three melted USB chargers from blackberrys & digital cameras, one at 5.0
>>> volts, 750ma; another at 5.0 volts, 550 ma, and yet another at 5.2 volts
>>> 450 ma.
>>>
>>> Can we swap these supposedly USB chargers or not?
>>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>>> - Motorola PSM5037B 5.9vdc 375mA
>>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>>> - Motorola FMP5185B 5.2vdc 450mA
>>>
>>> Why is Blackberry USB different than Motorola USB which is different in
>>> and
>>> of itself? Can we swap these USB chargers or must we stick to the
>>> charger
>>> that came with the device?
>>
>>
>> The current rating on a voltage source is the maximum amount that the
>> power
>> source can deliver without exceeding its saftey rating.
>>
>> What this means is that if you are using some device that has a power
>> supply
>> with a current rating of 500mA then its best not to use a different power
>> supply(at the same votlage rating) with a lower max current rating. i.e.,
>> anything < 500mA. Now ofcourse you might be able to get away with it but
>> if
>> it burns down your house then its your fault.
>>
>> A device will only pull the amount of current that it uses(assuming it is
>> a
>> voltage controlled device) and this is true regardless of the current
>> rating(hence the saftey issues I discussed above). If a device
>> says(sometimes they don't) it uses 500mA then it uses 500mA. Maybe it
>> doesn't use 500mA all the time but the engineers have put that rating
>> there
>> for a reason. Using any power supply with the right voltage and a
>> current
>> rating of anything more than what the device uses is ok because the
>> device
>> will only pull the current it uses.
>>
>> Now, about the voltage rating: The voltage rating does not have to be
>> exact
>> and different devices can tolerate different voltage ratings. The
>> problem
>> usually is one of current. By increasing the voltage, say, you increase
>> the
>> current the device uses and then you have changed the parameters that the
>> device was created with.
>>
>> i.e., suppose the device was created to work with 5VDC(a)1A. Now suppose
>> you
>> use a power supply that is 6VDC. The device will not draw 1A but more
>> than
>> one because of ohms law. It might draw so much more current that the
>> components will overheat or some other problems could happen. Not all
>> constant voltage power sources are equal... The voltage are not really
>> constant but the devices are usually designed to tolerate a small
>> deviation.
>>
>> So it may or may not be ok to use a different power source rated at a
>> higher
>> voltage. Usually you can get away with using a lower voltage rating but
>> when
>> you do this you decrease the current drawn by the device. It might not be
>> enough current to actually run the device. Having more than 1V over the
>> voltage rating is asking for trouble for most devices and even 1/2 a volt
>> might not be wise if you care about the device.
>>
>>
>> So, if you understand all that then your question is pretty trivial with
>> the
>> answer "It depends".
>>
>>> Can we swap these supposedly USB chargers or not?
>>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>>> - Motorola PSM5037B 5.9vdc 375mA
>>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>>> - Motorola FMP5185B 5.2vdc 450mA
>>
>> Each of these power supplies are designed for different device
>> requirements.
>> They do this mainly because its cheaper.
>>
>> you could get away with just one voltage source for 3 of the above:
>>
>>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>>> - Motorola FMP5185B 5.2vdc 450mA
>>
>> All could use a power supply of 5VDC(a)1A. This 1A rating gives enough
>> current
>> to any of the devices here and the 5V should work with the FMP5185B. 0.2V
>> might be to much though and cause some issues.
>>
>>> - Motorola PSM5037B 5.9vdc 375mA
>>
>> This is basically a 6V device. I doubt the 0.1V matters to much but it
>> could. Usually devices are not designed to be that tolerant because most
>> components are not very precise. You might even be able to get this thing
>> to
>> work off a 5VDC source but I'm not sure. It usually won't hurt to try as
>> long as it can supply the maximum rated current.
>>
>> i.e. for the PSM5037B you could try a 5VDC(a)375mA and see if the device
>> works. Ofcourse you could try anything above 375mA and it could work(even
>> slightly lower since we lowered the voltage). At most you will probably
>> fry
>> your power supply(but this could fry the device in some cases).
>>
>>
>> Ok, now for the practical side. Not all power sources are created equal.
>> Even two power sources at the same voltage and max current ratings can be
>> completely different. There are many types of methods of supplying power.
>> Usually your typical "wall wart" is just a piece of junk with nothing
>> special in it. If, say, you pull to much current from it then it can melt
>> but in the process increase the voltage which will cause more current to
>> be
>> pulled with could fry your device. (remember, increasing the voltage on
>> the
>> power supply increases the actuall current used by the device which could
>> go
>> over the maximum current that the power supply can safely supply.)
>>
>> If you have a need for many different power supplies then you might want
>> to
>> get one with selectable voltages. Here though you will need to make sure
>> you
>> don't hook any devices up that would draw more current than the power
>> supply
>> can give and that you always select the right voltage and polarity that
>> the
>> device needs.
>>
>>> Can we swap these supposedly USB chargers or not?
>>> - Blackberry TCPRIM2ULSSN 5.0vdc 750mA
>>> - Motorola PSM5037B 5.9vdc 375mA
>>> - Motorola DCH3-05US-0300 5.0vdc 550mA
>>> - Motorola FMP5185B 5.2vdc 450mA
>>>
>>> Why is Blackberry USB different than Motorola USB which is different in
>>> and
>>> of itself? Can we swap these USB chargers or must we stick to the
>>> charger
>>> that came with the device?
>>
>>
>> Now heres the exact answer why these are different:.
>>
>> The Blackberry draws a max of 750mA from its supply. If you use any of
>> the
>> other supplies they will burn out because they cannot supply the 750mA.
>> (they actually will try but burn out because it would get really hot).
>> Using
>> the PSM5037 on the Blackberry would be even worse than using the DCH
>> beacause the increase in voltage would increase the current used by the
>> Blackberry and surely draw to much current.
>>
>> The same idea applies to the others. The TCPRIM could be used for the
>> DCH3
>> and the FMP5185(probably) because it has the right voltage and gives much
>> more current than they need.
>>
>>
>> Whats would be really bad is to use say, a 10VDC(a)10A power supply on all
>> the
>> devices. Here the devices would surely be destoryed and not the power
>> supply.
>>
>> The reason is that the extra voltage would cause the device to consume
>> more
>> current which would cause it to get hotter and most likely hotter than it
>> was designed for. Since it uses more current and because most lilely the
>> power supply can supply that current(since it can do 10A) it will not be
>> destroyed first and hence the device will eventually overheat and fail.
>> Specially since most cheap power supplies do not have very good safety
>> precautions along with devices not having fuses and such(I'm sure they do
>> this so the device will be ruined if used wrong and would need to be
>> replaced).
>>
>> So while its ok to use a larger maximum current rating you have to make
>> sure
>> the voltage rating is correct too so you can't make the device pull any
>> more
>> current than it was designed for. e.g., a device that uses 5VDC and 500mA
>> will "always" use a *maximum* of 500mA at 5VDC and never any more(with
>> normal conditions). If you force it to use 7VDC then you also force it
>> to
>> use more current... maybe 750mA. The device was not designed to use this
>> amount and something will fail(either the powersupply or the device).
>>
>>
>>
>> Hope this helps,
>> Jon
>
> 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)?
>
> This implies that USB chargers are NOT interchangable!
> (The T-Mobile store clerks just might have been right.)
>
> But, what irks me is they all have the SAME CONNECTIONS!
> They all "LOOK" the same to me!
>
> 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?
>
> 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.
>
> Can someone clear up the USB part of the confusion here?
> Emily


From: Allodoxaphobia on 29 Dec 2006 14:17
On Fri, 29 Dec 2006 07:53:42 GMT, Emily wrote:
>
> But, what irks me is they all have the SAME CONNECTIONS!
> They all "LOOK" the same to me!

Standards are GREAT!! And, there are _so many_ to choose from.

Jonesy
From: Bill Funk on 29 Dec 2006 15:10
On Fri, 29 Dec 2006 07:53:42 GMT, Emily <emilymoberg(a)hotmail.com>
wrote:

>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.
>
>Can someone clear up the USB part of the confusion here?
>Emily

Nominally, they are all the same.
This means that as long as the connectors are standard, they will all
charge OK with the supplied voltage.
The problem that can occur is that the voltage and current is limited
at the *original* port; this means that if you are using a non-powered
hub, voltage and current may well not be up to the requirements of the
device.
--
Bill Funk
replace "g" with "a"
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