Z Is Dead, Wrong Polrity

[al_do]

I've made a big mistake: I've connected my Z to an AC-DC adapter with 4,5V output.
After that my Z died! I think it was wrong polrity....
Is it possible that it hasn't a protection again wrong polarity?
And what could I do now? thrash it? sob!

[Bundabrg]

Most likely you'll need to get it fixed (under warranty if its still in warranty).
The Z does not have any protection and whilst it may sometimes allow incorrect polarity, it will often blow some circuit. I've been through this

However, till its fixed, you can just charge the battery externally. A quick and dirty way is to pull the battery, and plug the positive terminal of the powerpack to the postitive on the battery, and the negative to the negative. It takes about 2 hours to charge fully, and from memory, measuring it with a multimeter, a charged battery is 4.2V.

[Pcghost]

You have, I assume, tried to do a hard reset?  If that fails remove all batteries from the Z for a few minutes and then replace them and try to reset again.  If that fails you are probably out of luck.  Does the charge led come on when you use the normal charger (from sharp), or do you not have one?

It is modern enough to have safeguards on its power plug, but that is no guarantee that Sharp included them.

[marshmn]

I often wonder why oh why manufacturers don't always design hardware
to work with any polarity input to avoid this sort of problem...

Surely this would be so easily done with a few diodes so cheaply and
would probably even save them money as they wouldn't have units to
repair under warranty from this problem...

Matt

[kopsis]

Surely this would be so easily done with a few diodes so cheaply and
would probably even save them money as they wouldn't have units to
repair under warranty from this problem...

It's usually a board real estate issue. Discrete components chew up lots of board space and that's even more true when they're sized to handle the relatively high current in the power circuits. The design engineers have size targets to hit. Since there's relatively little chance of the average consumer getting the power supply polarity wrong (that implies you're using something other than what came with the unit), big components that protect against such an "unlikely" event are the first to get the axe.

[ev1l]

However, till its fixed, you can just charge the battery externally. A quick and dirty way is to pull the battery, and plug the positive terminal of the powerpack to the postitive on the battery, and the negative to the negative. It takes about 2 hours to charge fully, and from memory, measuring it with a multimeter, a charged battery is 4.2V.

I very much doubt a li-ion cell rated at 3,7V will top at 4.2V
Although the Z adapter is rated for 5V at 2A, the internal voltmeter indicates about 3.85V when charging.
Li-ion batteries will blow in your face when overloaded. They need to be "topped-off" slowly.
Fix the damn Z, and don't fuck around with lithium batteries.

[Mahoro]

As I am still DIY-ing my Battery box...I wish I don't get the polrity wrong

[ran]

Surely this would be so easily done with a few diodes so cheaply

In addition to the real estate issue that kopsis mentioned,  there's another problem:  diodes aren't perfect conductors.  You lose a little voltage between the input and the output.  About .7V for the standard power-supply diodes,  and about .2V for the more-expensive Schottky diodes.

The "works either way" design requires an arrangement of 4 diodes that results in two diode voltage drops.  Losing 1.4V is no big deal when you're powering,  say,  a radio that can live with 9V off a 12V source.  But it's a huge problem if you're trying to charge a 3.7V battery from a 5V input.

The protective circuit would require either raising the input voltage (no more USB sync-n-charge cables) or adding an expensive circuit inside the Z to pump the voltage back up above 5V.

Basically,  the designs of PDAs that use 5V adapters and LiIon batteries are right up against the limits of what's physically possible with today's technology.  So you can have "cheaply",  or you can have "easily",  but not both at the same time    

Since there's relatively little chance of the average consumer getting the power supply polarity wrong

This,   actually,  has become a fairly serious problem in an increasingly-gadget-saturated world.  There's a voluntary industry standard (from JEIDA) for coaxial power plug sizes and voltages now,  but not everybody follows it:  And it only partly addresses our problem:  there's a range of voltages for each size,  which is mostly okay for radios and cassette players,  but not good enough for gadgets that expect a fully-regulated supply.  But at least it improves the odds against frying your toys if you mix up your adapters.

Ran

[Bundabrg]

Actually it would be useful if these universal power packs had their outputs keyed, so you can't put the plug in backwards. I don't mean keyed between the plug and the Z (though that would be nice) but keyed so when you put the end on to the end of the cable it only goes one way.

Honestly, are there any devices that have the polarity the other way?

Brendan

[ev1l]

Just checked on my Z, and a topped-off battery indicating 100% charged is reading 3.72V

[marshmn]

The power adapter I bought actually does have a notch which only allows the connectors to be added one way round...

Also, while we're at it, can we standardise on different voltages for different sized
connectors???

Matt

[speculatrix]

a few disparate points

there is a move by the IEEE to try and standardise cell-phone batteries.

Sony are one manufacturer who buck the trend of their power adaptors having the +ve on the outside of the tubular power plug... I think the majority have +ve inside the tube.

Always label lump-in-a-cord or wall-wart power supplies with the equipment they're to be used with, because they're so anonymous that if you get them mixed up you'll never know which ones for what. e.g. my modem, my ethernet switch, my palm power supply, my clie power supply and adsl modem's PSUs are all painfully similar.

LiIon batteries are potentially explosive devices, most have protection circuits inside to prevent explosion, but even so, you really don't want to risk it, the big 1100mAh batteries could in theory produce a big enough bang to destroy part of a house.

A $15 cheapie multimeter can prevent a mistake saving the life of an item costing ten times that amount.

Paul

[omega]

Part of a house you say - explain! 8-)   Nah, but how do you figure that?

[ev1l]

Part of a house you say - explain! 8-)   Nah, but how do you figure that?

Li-ion batteries need to be reloaded at a certain rate. You can load the first 60% or so as fast as you want, but they need to be topped off slower as you get closer to capacity, hance the need for a digital controller, or an intelligent charger).

Someone else can explain the chemistry bette rthan I do.

[ran]

Also, while we're at it, can we standardise on different voltages for different sized
connectors???

Yup:  see this webpage

I remembered wrong:  it's an EIAJ standard,  not JEIDA.

Ran