$1 million Google Tiny Box prize won

Belgian contenders The Red Electrical Devils have won the $1,000,000 Google Tiny Box prize.

There’s a .pdf of the paper describing their design here, but don’t bother trying to read it if the word “schematic” means nothing to you.

Google’s challenge was for a tiny, lightweight device that converts DC (the type of electricity that batteries and solar panels put out) to AC (the type of electricity that is most useful for doing work). Such devices are called “inverters” and improvements in inverter technology would obviously be useful for electric cars, home solar power systems, and many another thing.

The winning team exceeded Google’s minimum requirements to win by three times, creating a device that is ten times smaller than existing technologies while meeting all of Google’s other restrictions (such as 95% or better efficiency, air cooling, &etc.) It’s extremely impressive work.

Craptacular Eskimo Fan

Heather bought another old fan at the Arden Fair a few weeks back. It’s a single speed oscillating Eskimo with aluminum blades from the late 1930s. It has a somewhat attractive pseudo-Deco design with a spiderwebbish pattern to the cage.

Dissassembly revealed not only unbelievably thick crud deposits (half an inch of greasy fur inside the casing) but also the cheesiest design and materials I have ever seen in an antique fan.
The shaft bearings are thin and very yellow, very little copper content. But not all of the bearings are even metal! Some of them appear to be made of greased cardboard. The stator windings are literally bound with masking tape, although the wire nuts are porcelain. Two of the gears in the oscillator box are made of masonite – steam-pressed wood fiber. The worm gears they engage are steel, so don’t grab the fan and prevent it from oscillating unless you enjoy the sound of masonite gear teeth snapping off. The blade is soft aluminum, so soft that sticking a finger into the cage will almost certainly unbalance it… two of the blades are already bent, so that it vibrates noisily and the main shaft sidles erratically in and out like a trombone slide.

Even without the blade mounted it still sounds like a gravel crusher and the main shaft wobbles all over the place, because the squirrel cage rotor has never been balanced and all the cheesy bearing surfaces are worn out. If you push the oscillator shaft bearing up into the housing with a penknife it’ll swing back and forth wildly, at surprising speed, until the shaft bearing flys back out and the gearing disengages. I guess with a 2-pole stator and a 15-pole rotor you can’t expect smooth operation? The fact that the oscillator must have fallen apart almost immediately is probably what preserved those masonite gears.

Generous and repeated use of PB blaster, WD40, degreaser, and ultrasonics have given this piece of junk an interesting wabi-sabi patina that I kind of like, so I’m thinking about replacing all the bearing surfaces with bronze, and seeing if I can reshape the blade to restore balance. Planishing fan blades is always a big challenge, though.

Square D car charger after two months

Back in June I blogged installing a Square D Model EV230WS level 2 electric vehicle charging station.

The new charger is connected by 8 gauge copper wire with a NEMA 14-50 plug and receptacle, a Square D QO series safety switch, and a 40 amp breaker. The actual current draw of the charging station is 30 amps at 240 VAC, so I am still well within code for the 100 amp subpanel in the barn, and having the 14-50 plug means we can potentially support other 240 mobile loads like Teslas, large RVs, plasma cutters, and portable welders.

As promised, the system charges our plug-in Prius in roughly 1.5 hours, and the Nissan Leaf in 5. It’s very simple, no unnecessary bells or whistles, you just plug in and walk away. There’s no need for anything more complex, because the cars themselves both have externally visible charge indicators (the Prius just tells you if it’s done charging or not, but the Leaf gives you a rough indication of charging progress with three top-of-the-dash LEDs) and both cars can give you detailed charts and graphs of charging status and history from their on-board computer systems.

We’ve had a total of one unusual incident – last week the system lit its red “alarm” LED when the Leaf was plugged in. Since I installed it with a safety switch, it was easily rebooted, which cleared the alarm and restored normal function.

Last night a nearby lightning strike spiked our power, causing computers to reboot and making the HVAC system noisily unhappy, but the charger (which was plugged into the Prius at the time) didn’t seem to care much, it just rebooted itself and carried on normally.

All in all, we are quite pleased with everything about the charger except the price. All electric vehicle charging stations are ridiculously expensive right now, though, and at $600 the Square D EV230WS was the most cost-effective charger available without building our own.

Time Domain Reflectometry visualized

Wikipedia provides this excellent graphic to help explain how you can determine where the fault is in a very long cable.

Reflection of an electric pulse back towards point of origin

Time delay reflectometry is a clever trick where you can calculate the location of an imperfection in a conductor by timing when the “bounce” returns, as long as you know the speed of signal propagation in the wire (which you generally do).

The impedance of the discontinuity can be determined from the amplitude of the reflected signal. The distance to the reflecting impedance can also be determined from the time that a pulse takes to return. The limitation of this method is the minimum system rise time. The total rise time consists of the combined rise time of the driving pulse and that of the oscilloscope that monitors the reflections.

Plumbers will note that the behaviour of the electric flow here is analogous to water hammer. I think it should be possible to find the distance to an obstruction in a pipe as a TDR calculation, as long as you know how compressible the fluid medium is.

Installing a Square D Electric car charger

Since we’ve got two electric vehicles and a plug-in hybrid, it seemed like time to install a level 2 charging station.

After spending about six months studying the options, we decided on the Square D Model EV230WS which periodically goes on sale at Amazon and the Big Box stores (where shopping is a baffling ordeal!) for about $600.

Honestly, I don’t know if it’s really appropriate to call things “Square D” any more. The company was bought out by (nominally French) multinational megacorp Schneider Electric in 1991, after which they introduced the “homeline” series of circuit breakers and load centers, which are not as well regarded as the industry-leading QO series. But on the other hand, Schneider does still make the QOs, and they are still an excellent product family – I put a big QO breaker box in my house when I upgraded the main service a few years back, and I am very satisfied with it.

The new charger is connected by 8 gauge copper wire with a NEMA 14-50 plug and receptacle, a Square D QO series safety switch, and a 40 amp breaker. The actual current draw of the charging station is 30 amps at 240 VAC, so I am still well within code for the 100 amp subpanel in the barn, and having the 14-50 plug means we can potentially support other 240 mobile loads like Teslas, large RVs, plasma cutters, and portable welders.

Now the plug-in Prius should charge in 1.5 hours instead of 3, and the Leaf is supposed to drop from a totally impractical 16 hours (on the level 1 charger) to much more user-friendly 5 hours.

MPLS is back up, Cisco WIC at fault

Verizon wasn’t calling us back or being helpful for the first 24 hours while our network was down, so we starting yelling at them. After three hours of this, continuously on the phone with their support group, and working through four “escalations”, they eventually gave us some useful attention. With their help we determined that (unusually enough) the problem was not in Verizon’s equipment, although it’s not unlikely that the whole sequence of events started in their network. Embarrassing situation all around, really. Verizon did a great job once they got started, and from their point of view our system was the one failing and not theirs, but you still shouldn’t have to harangue people to get them to fulfill the most basic requirements of customer service.

Anyway, the MPLS circuit terminates at a Cisco 2811 router with 4 FastEthernet interfaces. The 2 port fast ethernet WAN Interface Card on that system was reporting completely false packet counts and diagnostics – pretending to work perfectly while actually generating no outgoing data packets at all, and ignoring all incoming packets. There was literally no way to diagnose this without using physical loopbacks and other caveman tricks since rebooting the router during business hours would wreak even more havoc.

Shutting down the router, pulling the power cord, reseating the WIC and restarting everything fixed it. But of course we had to fly Jay from Philly to Boston in order to do that, and the network was crippled for 41 hours before the situation resolved at right about 5AM. Three engineers working 19 hour shifts is not fun for people over 30!

Since clearly this WIC is unreliable we moved the line to a dedicated port and set up a hot spare router next to the problem child.

Have some π

HiFiBerry, tiny add-on boards bringing high quality sound to the Raspberry Pi

piCorePlayer, a dedicated Squeezebox player (like a Logitech Duet) for Raspberry Pi

RasPiO, a family of add-on I/O boards for the Raspberry Pi

HDMIPi, an affordable 9″ high definition screen for the Raspberry Pi

Homebrew wall-mounted Raspberry Pi powered touchscreen Squeezeplayer

Electric Motors Undressed

I find the variety of electric motors to be remarkable, and the textbook explanations of their operation nearly impossible to relate to any particular motor I’m trying to fix. Usually I don’t know why it works, even after I fix it, unless I take a week to study it, and I rarely have that kind of time. The diagrams in the references never look anything like the real motors!

Enter John Storey of the University of New South Wales Physics Department, and his brilliant How Real Electric Motors Work web pages.

Americans will have to remember that mains frequency in Oz is 50 Hz – hereabouts, line frequency is 60 CPS.

and the wires came down

Yesterday a big limb fell and landed on the overhead wiring connecting the barn and house. The elderly ceramic strain relief did not fail or pull out.. instead it ripped the corner board right off the house, shingles a-flying. Pictures soon.

The wire then apparently rebounded like a trampoline and fired the limb back into the air, and it ended up down below the deck where you couldn’t see it from the walkway.

So when I came home the wiring was drooping across the deck and caught in the top of the service berries with naily boards dangling from it, and despite a sprinkling of busted cedar shingling and sycamore twigs, no obvious sign of how this happened. I couldn’t figure it out until I found the limb laying below the deck in a smash of daffodils and daylillies.

The power was still on in the barn and the wires seem reasonably intact – no obvious stretching or insulation damage. I need to bury that thing one of these days.