How a Leather Cover Crashes the Kindle 280
An anonymous reader writes "Amazon has started offering refunds to Kindle owners who own the unlit leather case who claim that it causes their Kindles to reboot, but are playing dumb on the cause: "our engineering team is looking into this." People have been wondering how a leather cover could possibly crash an electronic device, and why is Amazon offering money back if they don't think there's a problem? It seems that some of the folks over at Connectify have figured it out, and it's a doozy!"
Not unprecedented (Score:5, Interesting)
http://ftp.sunet.se/jargon/html/magic-story.html [sunet.se]
Re:Yikes! (Score:5, Interesting)
It looks like a flaw on the part of the cover maker. Amazon could put some amperage limiting circuitry, but I imagine it would raise the cost.
Look closely at the dudes meter, its 2 megohms not 2 ohms. Lets guess its a single cell li-poly at 3.7 volts. Thats a smokin' current of 74 microamps. What, a quarter of a milliwatt, something like that?
Good luck building a 74 microamp fuse. I once built a microwave preamp in the 80s and static fried the active device, that probably was a 74 microamp fuse, in a weird sort of way.... Active current limiting at that level is kind of a mystery to me... I suppose you'd need a mosfet off resistance in the hundreds of megohms since the load impedance is in the single megohm range, but PC board leakage currents are going to be a problem at that level. Leakage currents thru the plastic kindle case would probably be in the microamp range?
Re:Not unprecedented (Score:5, Interesting)
So much for magic.
Re:Yikes! (Score:5, Interesting)
You suppose wrong.
We used AA batteries in prison to light cigarettes when they took away access to the wall sockets.
Re:Metal hooks? (Score:4, Interesting)
Being a product manager, I would guess that whomever wrote the spec for the cover latch, specified dimensions, and what is required for it to be a sturdy fit. But that they forgot to specify that there was to be no electrical connection or conductivity between the tabs.
The Winning bidder probably chose to make the bracket out of brass (guess here) to ensure dimensional integrity, and because a plastic mold for a thermoplastic injected part would be a couple tens of thousands of dollars.
But, I would bet my last dollar that someone at QA at Amazon figured this out, and specified that the bracket had to be painted with a non-conductive paint as a band aid.
This is how trivial, serial bad decisions come back to bite you in the arse
Had an interesting issue with my iPad cover (Score:4, Interesting)
I got a Marware cover for my iPad and love it. One issue it had though, was that the iPad's compass simply never worked. It always gave me the Figure-8 Shake warning, and I eventually thought that perhaps my iPad was defective... Then one day I noticed that the flip out "foot" in the cover is held in place by two magnets. Whoops. Really only an issue if you use a compass app or if you want to figure out directions while not moving, but an interesting design issue none-the-less.
Re:He's got it all wrong (Score:5, Interesting)
Reminds me of the Garmin Edge reboot and USB connectivity problems. They didn't use a flex to connect the rear case electronics to the front case electronics, they used a riser with flexible fingers. Fair enough, but they integrated this riser with the mini-USB port jack, and because of that surrounded the case opening with a thick gasket of stiff rubber. See what's coming? When the case is closed, the gasket puts a high spring force between the two circuit boards right where the fingers are mounted, reducing the spring force the fingers can apply to their mating contacts. When using the unit in a vibrating situation (you know, like on a bike, especially an MTB in typical MTB terrain), intermittent loss of contact results in power-bus glitches, which results in inadvertent power-cycling. And these things boot slower than a netbook running Windows Vista, so not only is it wearing on your data-gathering sensibilities, it's fracking boring waiting for the thing to come back to usable state so you can sweat while you wonder if it'll blow itself out again.
Also, repeated insertion and removal of the USB connector leads to loose USB connectivity, and reboots while plugged into the computer.
It took Garmin nearly a year to "figure it out", while everyone online who knew what the insides looked like knew within seconds what was going on. And Garmin's solution was to introduce the next model (at 3X the price). People owning the buggy model were offered a chance to mail in the device for a fix, but most were out of warranty, and the fix was not reputed to be a sure one.
Moral: Never -- ever -- trust a corporation when the potential for money flow is negative to them.
Re:KaWow (Score:5, Interesting)
How exactly do you fry an ebook?
A demonstration for you:
1) Purchase Kindle
2) Purchase and download 1000 ebooks to Kindle
3) Throw kindle into incinerator
4) Purchase new Kindle and click "Sync"
5) 1000 ebooks "magically" appear on new kindle and more remarkable show no signs of fire damage.
Re:He's got it all wrong (Score:1, Interesting)
Ahh Khyber, you still around? Mods Khyber is a troll, who claims crazy stuff, please see his previous posts before modding him up!
Re:Yikes! (Score:5, Interesting)
His fingers appear to be touching both metal probes of the meter so 2 meg-ohms seems about right for his internal resistance.
Re:He's got it all wrong (Score:4, Interesting)
First, his meter's reading 2 Megaohms, not 2 Ohms. I guess he's not much of an "Electronics Person"
Maybe he's not much of a "Photography Person". It's not easy to snap the shot while holding two probes in contact with the metal hooks. The photo is there to give an idea of how it went, it's not supposed to be an accurate document of the measured value.
The "non-electronic" persons are those who calculated the electric resistance of the metal hooks. I got my EE degree in 1979 and have been an electronic hobbyist since 1969 and I know that 2 ohms is typical of what you may get from measuring a short circuit. There's always some dirt and oxide around, it's not usual to read the true resistance of the metal itself.
The old AS400 and the Elevator (Score:5, Interesting)
I used to work on an old IBM AS400 which provided about 150 terminals (5250) to a bank. At random times, all of the terminals would lose connection to the AS400 which was located in the datacenter which was located in the floor below where everyone sat. The connections would only drop during the daytime, we could hook up all sorts of diagnostic equipment at night and almost never saw a drop.
After about 2 weeks of troubleshooting we determined that every time the elevator passed the cable infrastructure which was run down the elevator shaft, it would cause the terminal sessions to drop...
Imagine everytime you left the building at 2am after not being able to find a problem; to have someone call you and say "just as you were leaving the terminals reset..."
Re:He's got it all wrong (Score:3, Interesting)
Another IBM/Radar story. (Score:5, Interesting)
IBM 4341 mainframe in our data-center that would just shut down regularly every Friday night, around the same time ... shutdown coincided with the approach of the USS Lexington ... Apparently the radar from the ship was strong enough to ... trigger a shutdown.
Another IBM radar story (Third hand: CE involved -> my brother -> me.)
Shortly after the "Foreign Attachments" suit required IBM to allow other companies' equipment to be directly connected, there were a number of multivendor projects, of which this was one.
Each component worked fine in the respective labs. But the first integration of the whole system took place at the final site. (Why rent some space, hook it all up, get it running, tear it down, move it, and hook it up again, when you can do it once at the final site?) So they hooked it up and nothing worked right.
Several weeks of hair-tearing and finger-pointing by exasperated CEs from several companies ensued. At one point my brother's buddy had time on his hands and decided to fix the really annoying flickering fluorescent tube. He turned off the lights - and the tube kept flickering. WTF?
He called the other CEs over and demonstrated this. Then they all took a quick look around the environment to see what might be causing it. It was a short look: The wooden building was right next to the antenna for the airport's search radar.
Lined the room with conductive material. Everything started working just fine. Handshakes all around, exit stage left.