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Ask Slashdot: Where Can I Find Good Replacement Batteries?

hamjudo Re:Variation in online reviews (131 comments)

Sometimes the variations in reviews is due to variations in the product. Many years ago I worked in a brick and mortar store and resold electronics. I'd buy a small number of units from a supplier and test them. If they were good, I'd buy a bunch for resale. Assuming the customers didn't bring them back, I would buy more of the same, from the same vendor. Customers who were happy with units from the first few batches, were not at all happy with units from later batches.

I dissected customer returns. Again and again, the products in later shipments looked identical on the outside, but were "cost reduced" on the inside. For example, I would see empty places on the circuit boards where the filter capacitors were supposed to go. In one batch of one product, many of the units were dead on arrival, on the ones that worked when I unpacked them, the solder joints only lasted a few weeks. Once opened, I could see that the boards were either soldered at the wrong temperature, it was the wrong type of solder, or badly made solder. Every connection was visibly a cold solder joint. Either the factory had no quality control, or they ignored the quality control.

Other products looked identical inside and out, but based on the failure rate, the factory must have gotten a bad batch of one the components.

Even longer ago, I worked on a product that logged data to a Compact Flash memory card. It was an embedded product that needed to work across a wide temperature range, including in the winter in Minnesota. The big names like SanDisk would randomly swap component suppliers. Our largest customer saw less than a 2% failure rate, but that was way too much. We found a specialty supplier that charged 5 times as much, but they had a rigorous quality control process. They paid attention to the specifications. They tracked where parts came from, and promised that we would be able to test sample units if they needed to switch suppliers. Alas, the 2% failure rate from the earlier parts had already doomed that product line.

about a month ago
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3D-Printed Material Can Carry 160,000 Times Its Own Weight

hamjudo Re:This is not really new (60 comments)

The Fine article compares this type of lattice structure to the structure of the Eiffel Tower. They didn't claim anything more than being able to do it at a very fine scale, and to do it sufficiently precisely to get something that can support 160,000 times its one weight. They are just claiming refinements on centuries of engineering advances. The strength of well engineered 3D printed structures is still impressive. Even some printers that hobbyists can afford can beat out solid materials. It's only getting better.

about 3 months ago
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Intel Rolling Out 800Gbps Cables This Year

hamjudo It is all a matter of cost and size (101 comments)

These will be used in data centers where it is common to have redundant systems connected with redundant cables, in order to maintain really high uptimes. Say a hypothetical system has a cluster which consists of 16 compute nodes and 2 storage nodes, Each of CPUserver01 through CPUserver16 will have two of these cables going to storageServerA, and two going to StorageServerB. For a total of 64 of these cables, for that one little compute cluster. Which would leave it an island, so of course there will be more network interfaces.

For this technology to get any market penetration, it will need to be cost effective at these bandwidths, and fit in the racks. Historically, Dense Wavelength Division Multiplexing, DWDM has been great at getting a lot of bandwidth on to a very long single strand (comparatively) inexpensive fiber, which allows in fiber signal amplification, and is the winner at going the distance, but not so good at being cost effective, or space efficient. These things, with the associated drivers should take up far less space inside the servers, and cost less, but they only will get 800Gbits in each direction, only go 300 meters, and use much more expensive (per kilometer of cable) 64 strand fiber.

about 6 months ago
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Hard Silicon Wafers Yield Flexible Electronics

hamjudo Re:What's the killer app for flexible ICs? (15 comments)

Rigid silicon requires rigid interconnects. Flexible ICs allow flexible packaging, or different packaging. Instead of building from the printed circuit board up, build from the heatsink up. Use a precision pick and place system to glue the thin, wimpy, inexpensive silicon to the strong massive heatsink. Then mask on the solder balls. Then apply a thin, wimpy, inexpensive circuit "board". Attach all the old style surface mount components to the other side of the circuit "board". "Board" is in quotes because it would get all of its mechanical strength from heatsink. It might be so thin, it is no longer board like.

The big win here, is that one wafer is good for at least 5 sets of circuits. The lose is the grid of holes etched through the silicon as part of the pealing process. Assuming the grid of holes doesn't use up a significant portion of the surface area, the factory is getting close to 5 times as many devices out of each ingot of silicon.

about 6 months ago
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Revolutionary Scuba Mask Creates Breathable Oxygen Underwater On Its Own

hamjudo It is a student design project (3 comments)

You can see the student's portfolio on his website: cargocollective.com/jeabyundesign/TRITON . He probably got a good grade. The case looks nice, if not plausible. The design for the guts of the device is lacking. He got the biology wrong, divers don't want pure oxygen. They need a mixture of gasses. The machine would have to process a whole lot of water to get enough oxygen to support a human. This means a whole lot of water would have to continuously flow through the device. Moving that much water takes a lot of energy.

about 8 months ago
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Website Checkout Glitches: Two Very Different Corporate Responses

hamjudo Real time double entry bookkeeping (303 comments)

A few trading firms have learned to have a second system that monitors transactions to keep tabs on profit and loss. If the things swing out of the expected range, it is time to have a human look at the situation. If things get really out of hand, it is time to rate limit transactions, or halt them out right. Sudden extreme profits usually indicates a data entry error on your system, not that the rest of the market has gotten really stupid.

Most inventory systems have a way to track cost of goods, age of inventory, and expected profit margin. Eventually retailers will start filling in those details, and tracking them, so they can notice when something goes expensively wrong.

about 9 months ago
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Google Nexus Gets Wireless Charger

hamjudo I've got a Qi charger (223 comments)

It works even if my Nexus 5 is more than 5 mm above the charging pad. That is many orders of magnitude less than the range for most wireless communication technologies.

The useful features are

  1. no connector to wear out,
  2. alignment is simple.
  3. The USB/thinport connector is available for other uses. (More of a theoretical benefit, as I don't use the USB port for anything, but I could if I wanted to. I've got the cable, I could even plug in an SD card reader.)

about 10 months ago
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Not All USB Power Is Created Equal

hamjudo Re:won't help for Samsung note 2 (240 comments)

The error was an extra "m". The poster meant 0.14 Ohms per meter. I've seen higher resistance USB cable than that in the real world. Think of how much copper they saved by using such thin wires...

about 10 months ago
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How Your Coffee Table Could Pass Your Coffee

hamjudo sort my Duplos (55 comments)

I was going to use the subject, Sort My Legos, but the prototype resolution is too low. With more actuators, you could dump Lego bricks on the table and have it sort them for you. Or for the more practical minded, sort wrenches, nuts and bolts.

about 10 months ago
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AMD Intentionally Added Artificial Limitations To Their HDMI Adapters

hamjudo Re:HDMI has limitation built in to the spec (256 comments)

I have a monitor hooked up to my ComCast cable box in the exercise room. After I exercised for a while, I would get the stupid HDCP warning and/or the video would just cut out. I switched cables, I switched HDMI - DVI adapters, I switched monitors. It seemed like every time I started exercising, the video would stop.

It got worse recently, making it easy to diagnose. It got to the point where the video went away within a second of starting the treadmill. It is an EMI issue. Either the treadmill is emitting too much, or the ComCast box's suicide circuit is too sensitive.

I am so pleased that my ComCast has a suicide circuit to protect me from evildoers who modify treadmills to steal valuable copy righted material.

about a year ago
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Bell Labs Break Record With 31Tbps Via a Single 7200km Optical Fibre

hamjudo Re:The TRUE test (125 comments)

The station wagon can outrun a backhoe.

about a year ago
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Cray X-MP Simulator Resurrects Piece of Computer History

hamjudo Re:simple load (55 comments)

You need a 3 phase load. That is going to take some careful bolt placement to get the 3 phases matched.

Remind me never to visit your neighborhood.

about a year ago
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Cray X-MP Simulator Resurrects Piece of Computer History

hamjudo Where is the power load? (55 comments)

For the complete simulation, you need to use a generator load tester to burn the 100 or so kilowatts that the machine used.

about a year ago
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Popular Android Anti-Virus Software Fooled By Trivial Techniques

hamjudo Re:This just in! (94 comments)

Virus 'signatures" are an ideal technology for dealing with common threats from the late 1990s.

about a year ago
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Xkcd's Long-running "Time" Comic: Work of Art Or Nerd Sniping?

hamjudo really long science fiction short story (190 comments)

The characters built some stuff on the beach, and now they are wandering around trying to figure out how their world works Their world does not work like our world.

The form of story is unusual, in that one must use additional technology to follow it. Which the reading community developed very quickly. I use xkcd.aubronwood.com/.

about a year ago
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The Smart Grid Has Arrived

hamjudo Re:The Smart Grid Has Arrived (121 comments)

Stealing power takes a certain level of knowledge and attention to detail. Quite a few power thieves manage to send themselves to the emergency room or morgue each year. This is far more common in regions where the theft rate is so high that the power companies install the brains of the meters on the pole transformers. They just put a remote display on the residence.

about a year ago

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I took down the wireless link

hamjudo hamjudo writes  |  more than 12 years ago

The roofers are coming tomorrow to rip off the old roof and put in a new one.

So I pulled the Pentium 90 with the 802.11 antenna out of the attic tonight. I bet it could handle some wind and a little rain, but there will probably be amazing amounts of dust.

Dave's internet connection will be down until Friday.

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