How do you fix a shorted cable ? Not just any cable. An underground, 3-phase, 230kV, 800 amp per phase, 10 mile long one, carrying power from a power station to a distribution centre. It costs $13,000 per hour in downtime, counting 1989 money, and takes 8 months to fix. That’s almost $75 million. The Los Angeles Department of Water and Power did this fix about 26 years ago on the cable going from the Scattergood Steam Plant in El Segundo to a distribution center near Bundy and S.M. Blvd. [Jamie Zawinski] posted details on his blog in 2002. [Jamie] a.k.a [jwz] may be familiar to many as one of the founders of Netscape and Mozilla.
To begin with, you need Liquid Nitrogen. Lots of it. As in truckloads. The cable is 16 inch diameter co-axial, filled with 100,000 gallons of oil dielectric pressurised to 200 psi. You can’t drain out all the oil for lots of very good reasons – time and cost being on top of the list. That’s where the LN2 comes in. They dig holes on both sides (20-30 feet each way) of the fault, wrap the pipe with giant blankets filled with all kind of tubes and wires, feed LN2 through the tubes, and *freeze* the oil. With the frozen oil acting as a plug, the faulty section is cut open, drained, the bad stuff removed, replaced, welded back together, topped off, and the plugs are thawed. To make sure the frozen plugs don’t blow out, the oil pressure is reduced to 80 psi during the repair process. They can’t lower it any further, again due to several compelling reasons. The cable was laid in 1972 and was designed to have a MTBF of 60 years.
Continue reading “Find and Repair a 230kV 800Amp Oil-Filled Power Cable Feels Like Mission Impossible”
Digital White/Black Boards or “Smart Boards” are very useful in modern classrooms, but their high cost often makes it difficult to convince administrators from loosening their purse strings. Cooper Union’s 2nd annual HackCooper event in New York wanted students to design and build hardware and software projects that both solve real problems and spark the imagination. At the 24 hour hackathon, the team of [harrison], [david] and [caleb] decided to put together a low-cost and simple solution to digitizing classroom black board content.
A chalk-holder is attached to two strings, each connected over a pulley to a weight. The weights slide inside PVC pipes at the two sides of the black board. Ultrasonic sensors at the bottom of each tube measure the distance to the weights. The weights sit in static equilibrium, so they serve the purpose of keeping the string taut without negatively interfering with the writer.
With a couple of calibration points to measure the extent of displacement of each weight, board width can be determined, making it easy to adapt to different sizes of boards. Once calibrated, the system can determine position of the chalk over the board based on some trigonometrical calculations. Since they had just 24 hours to hack the system together, they had to use a hand operated radio with a couple of buttons to provide user control. Pressing the “Write” button starts transmitting chalk movements to the digital screen. A second button on the radio remote serves to “Erase” the digital screen. After receiving the chalk position data, they had to do a fair amount of processing to eliminate noise and smooth out the writing on the digital screen.
A server allows the whole class to receive the chalk board data in real time. After each “Erase” command, the chalk board state is saved and logged on the server, thus allowing previous content to be viewed or downloaded. If only text is written, optical character recognition can be used to further digitize the content.
What makes the project really useful is the low cost. The sensors cost a dollar. The other parts – PVC pipe, weights/pulleys, Arduino and the Radio key fob – were all bought for under 40 dollars. For some additional cost (and maybe more time in their case) they could have automated the detection of when the chalk was actually doing the writing. The team have made their code available on Github. For a Chalk board at the other end of the cost spectrum, check this one out. Video below.
Continue reading “Blackboard digitization for under $40”
[Anurag] is a computer engineering student with a knack for rollerblading. Rollerblades are not a transportation device that are often fitted with speedometers, so [Anurag] took that more as a challenge and designed this Arduino-powered computer to give him more information on his rollerblade rides.
The device uses an Arduino as the brain, and counts wheel revolutions (along with doing a little bit of math) in order to calculate the speed of the rider. The only problem with using this method is that the wheels aren’t on the ground at all times, and slow down slightly when the rider’s foot is off the ground. To make sure he gets accurate data, the Arduino uses an ultrasonic rangefinder to determine the distance to the ground and deduce when it should be taking speed measurements.
In addition to speed, the device can also calculate humidity and temperature, and could be configured to measure any number of things. It outputs its results to a small screen, but it could easily be upgraded with Bluetooth for easy data logging. If speed is truly your goal, you might want to have a look at these motorized rollerblades too.
As anyone with a Facebook account that’s over the age of 25 will tell you, 3D ultrasounds of fetuses are all the rage these days, with ultrasound pictures of the unborn recently taking the leap from black and white blobs to 3D – and 4D – images. With the advent of 3D printers, the inevitable has happened. Now you can order a 3D print of your yet-to-be-born progeny.
The company behind this – 3D Babies – takes 3D ultrasound data from weeks 24-32 and turns it into a 3D model. The printed 3D models sell for $800 for the full size version, $400 for a half-size version, and $200 for a quarter size version. It appears the 3D ultrasound data is simply wrapped around a pre-defined mesh, so while the resulting print may come out looking like your spawn, it’s still not a physical copy of the 3D/4D ultrasound data.
Despite the ‘creepy’ factor of these little bundles of plastic, we’re wondering why we haven’t seen anything like this before. Are there any obstetricians/radiologists/ultrasound techs out there that have experience with importing 3D ultrasound data into an editor of some sort? Notwithstanding any HIPAA violations, it seems it would be rather easy to turn this sort of 3D data into a printed object. 3D printing CT scans models can’t be the only other instance of this type of thing.
Thanks [Will] for the nightmares
Vintage electronics are awesome, and old medical devices doubly so. When [Murtaugh] got his hands on an old ultrasound machine, he knew he had to tear it apart. Even if he wasn’t able to bring it back to a functional state, the components inside make for great history lesson fifty years after being manufactured.
This very primitive ultrasound machine was sold by Siemens beginning in 1963 as a, “diagnostic ultrasound unit for the quick evaluation of cerebral hemorrhage after accidents.” This is barely into the era of transistors and judging from [Murtaugh]’s teardown, nearly the entire device is made of vacuum tubes, capacitors, and resistors. The only solid state component in this piece of equipment is a bridge rectifier found in the power supply. Impressive stuff, even today.
In the end, [Murtaugh] decided this device wasn’t worth repairing. There were cracks all the way through a PCB, and he didn’t have any of the strange proprietary accessories anyway. Still, this junkyard score netted [Murtaugh] a bunch of old tubes and other components, as well as a nifty CRT that came with a wonderful ‘Made in West Germany’ label,.