USB power supplies.

Using a mini-USB connector to power things from a PS seems to be quite common these days for things like phones, Tom-Tom, etc. Presumably only using some of the 'pins' on the connector as there is no data being transferred. Are they universal? Assuming the PS supplies enough current will any one work with another, as it were?
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Dave Plowman (News) wrote:

The data pins may be shorted, or have a known resistance across them to act as a secret handshake for certain devices to take more current.

iThings seem to be different to most other things.
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Dave Plowman (News) wrote

In my experience - no. I have a Hudl, I attempted to charge it with the wrong charger that had an identical (or so I thought) USB cable connection, it failed and I thought the Hudl had a problem, until I used the correct charger and cable.
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On 01/08/2014 13:15, Dave Plowman (News) wrote:

Not quite. But close enough that I use mine pretty much interchangeably.
Some USB3 are capable of supplying nearly 900mA whereas the standard USB2 ones are only good for 600mA and weedy PSUs might not manage that.
Smart devices wanting more power are supposed to negotiate with their host to get it, but some things just go gimmee gimmee gimmee.
The general rule of thumb is that they mostly work interchangeably but it may take a longer to recharge a power hungry device from a weedy USB PSU. It is the assumption that all can supply the correct current that might be an issue. Some power hungry peripherals have a pair of USB connectors on them so that they can take current from two USB sockets.
It is a *HUGE* improvement from the early era of mobile phones when every manufacturer and model seemed to require a different charger, voltage and physical connector with ever more peculiar shapes!
Shame that laptops are still not fully standardised. I have collection of old PSU blocks for them in a drawer ranging from 14v up to 19v. Mostly centre positive but you can't take it for granted!
Regards, Martin Brown
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On Friday, August 1, 2014 1:32:42 PM UTC+1, Martin Brown wrote:

In practice differing voltages are largely interchangeable. Trouble is there's no way to know for sure when they are.
NT
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On Friday, August 1, 2014 8:32:42 PM UTC+8, Martin Brown wrote:

I have 2 Nokia phones. The charger is the same voltage, but new one has a smaller plug that is easier to break.
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I'd agree with Martin that supplies and devices are *mostly* interchangeable - but I don't have anything from Apple, which probably helps!
I've successfully charged phones, satnavs, e-readers etc, from each others supplies, and from desk PC's and (esp. away from home) a netbook.
One very good thing about the USB standard is that the voltage concerned is always 5 volts at a specified polarity, irrespective of current availability and odd resistor "fiddles", so it's reasonable to assume that even if a device isn't properly charged from a particular supply - no harm will be done.
Charles F
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Thanks for that - gives me confidence to try it. If there's no chance of magic smoke.
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On 01/08/2014 14:08, Dave Plowman (News) wrote:

Not charger related - but 3 easily done 'wrong USB connections'
# On some devices the micro USB socket is not that sturdy and it is possible to insert plug upside down.
# You can plug standard USB plug into an Ethernet socket (not good)
# You can plug standard USB plug into a PC USB socket the wrong way round ...
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On 04/08/2014 07:57, Rick Hughes wrote:

Which would result in no connection, looking at the ones here.

Not good for the ethernet, maybe, as it would short it out and possibly bend the contacts, but no problem for the USB, unless it's one of the rare unshielded ones that I've seen on thumb drives.

That takes a fair amount of force. Enough to damage both plug and socket.
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On Fri, 01 Aug 2014 13:15:31 +0100, Dave Plowman (News) wrote:

One gotcha, is car chargers. I use my Nokia 620 as a satnav, and noticed that when it was "charging" from the 12V USB adapter, it slowly lost charge until dying.
Swapping chargers with my wifes phone (which was marked "1A", whereas the orginal was unmarked) fixed the problem, and now I can satnav all day *and* charge the phone.
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On 01/08/2014 14:08, Dave Plowman (News) wrote:

The only risk of magic smoke is if you plug something impolite about taking maximum permitted current without bothering to ask into a USB socket on something smart that is weedy and unable to comply.
Most times the worst that will happen is that the USB charger will be slower than it should be because it can't source the same current as the units proper charger. It helps now that cars have USB sockets.
Given the short battery life of smartphones you can't afford to be too picky about where you charge them...
Regards, Martin Brown
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On 01/08/2014 15:54, Martin Brown wrote:

Unlikely, as the chipset on the output side *should* limit the available current independently of any negotiation, so even a dead short across the power lines won't cause damage. Similarly, the chipset on the input side will limit itself to what it can take safely.

True.

One reason I like Nokias, as they tend to have better battery life.
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On 01/08/2014 16:23, John Williamson wrote:

Not meaning to pick you up too much on a very reasonable generalisation. My Nokia 925 was the absolute worst phone on the planet when running any navigation app. I managed to flatten in under an hour despite being plugged in to an external battery pack as well. My Nokia 1520 is pretty damned good almost whatever you run on it.
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On 01/08/2014 16:23, John Williamson wrote:

I agree that it shouldn't happen in well designed circuits, but I have my suspicions about some cheap budget stuff cutting silly corners.

There is a chance that some high draw devices like satnavs might continue to discharge their own battery if the PSU is inadequate.

Me too. I kept a 6303 going until last year when I discovered the hard way that it doesn't like being dunked in a bucket of water. The battery life was phenomenally good nearly two weeks running on a single charge.
Some folk I know have to recharge their smartphones at lunchtime... I suspect CandyCrush Saga is a battery thief!
Regards, Martin Brown
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On 01/08/2014 16:48, Martin Brown wrote:

As they all seem to use the same chipsets, I'd expect it to be rare, as long as the makers use the reference design, which seems to be a single chip on a PCB, with a tiny coil and couple of other bits with some suppression components if you're lucky. All the current limiting and control logic is on the chip, with everything preset and no adjustments for the manufacturer to get wrong.

Just don't ask how *I* know this....

Even the Lumia 520 I bought recently lasts me a couple of days, but I'm a light user.

Not to mention all the other games that phone home to download the adverts that pay for them.
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They don’t actually. The worst of the non genuine chargers don’t even bother to use any chipset at all and just use a single discrete transistor for the 'regulator' and if you kill that, you can end up with the full unregulated voltage being delivered to the device being charged.
That’s been proven with destructive testing on youtube.

The worst of the non genuine chargers don’t.

Pity about the non genuine chargers that don’t even bother with the chip at all to save a few cents over a single transistor.

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And some of the teardowns and destructive testing of smartphone chargers on youtube shows that the worst of them are utterly obscene and not only don’t bother about protecting the charger, they can fail in a way that destroys what is being charged in the process of dying basically as the 'regulator' of the 5V output delivers the full unregulated voltage to the device you are attempting to charge.

But it turned out that even something like the N95 had a pretty pathetic time on battery.

And you didn’t get anything like that with the N95.
And now there is fuck all on the way of decent android phones from Nokia anyway.

Yeah, the obsession with super thin phones by clowns like Apple is the main reason for that sort of utter stupidity.

Its quite possible to run the battery flat in a couple hours in a garage/yard sale run that starts in the dark so you need to use the torch a bit.
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On 01/08/2014 13:15, Dave Plowman (News) wrote:

Actually, I disagree. I think micro-USB is very common on phones, mini-USB less so. Other devices vary somewhat unpredictably.
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On 01/08/2014 19:06, polygonum wrote:

It seemed to go from weird and wondeful to mini uSB to micro USB. I was told that it has recently been decided to standardise on micro USB for all devices using a USB connnection for power and data.
Until theybuggrem change their minds again...
(Apple are of course excluded from this generalisation)
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