WhirrrrrCLUNK

Posted on 2011-08-10 by M. Eric Carr

Dear City of Philadelphia,

I like classic technology as much as you do. Probably more, in fact. But even I know how unreliable older technology can sometimes be, especially when it most likely hasn’t been replaced in a long time — because it most likely hasn’t been produced in a long time.

Classic technology can be a way to remember the best parts of our past, and can even provide entertainment (and draw tourism dollars, like vintage steam-engine railroads can.) But when the technology in question is part of our infrastructure, perhaps a bit of preemptive upgrading is called for.

Specifically, when you walk past a traffic light timer and it makes a “whirrrrCLUNK” sound while changing from one cycle to another, this means that inside that box is a set of electromechanical contacts, a motor, and a gear train probably old enough and curmudgeonly enough to run for Congress. Motors, gears and contacts — having moving parts — wear out. Most likely (hopefully) the light is designed to fail into one valid position or the other — or at worst, an all-red condition — but this kind of design is why “stuck” lights happen. The whole thing could be replaced, at low cost, with a microcontroller and FET board. Heck, making a working traffic light system out of an Arduino and custom shield would be a suitable project for an undergraduate course in power electronics.

Let’s swap these things out and donate them to the “Please Touch” museum and local high-school classrooms so kids can see what vintage electromechanical technology looks like. Designed properly, a digital solution (as no doubt is used in new installations) would not only be much more reliable, but could allow for timing variations based on the time of day or day of the week, traffic flow, and weather conditions. Given an Internet connection (conveniently available with another popular shield, in the case of an Arduino solution), it could even coordinate with other nearby traffic lights and help smooth the flow of traffic.

But this is Philadelphia. We can’t even keep people from smoking in our subway stations. I can’t imagine traffic light reliability is high on anyone’s agenda. Maybe someday.

Sincerely,
Your friendly neighborhood Paleotechnologist

 

Posted in Arduino, Digital, Digital Citizenship | Leave a comment

HDR: Moving beyond “megapixels”

Posted on 2011-08-05 by M. Eric Carr

Since the first digital cameras came on the market (I got my first one — an ancient 640×480 Vivitar — back in 1997), resolution has continued to improve. Modern cameras with more than ten million pixels (10 megapixels, or MP) are available for a few hundred dollars.

One drawback of digital cameras, though, has generally been a lack of dynamic range. For example, if you take a picture of a lump of coal next to a bare lit lightbulb, chances are that either the coal will be digitized as completely dark, the lightbulb will be digitized as at maximum brightness, or both. There just isn’t much dynamic range (number of distinct levels between the brightest and darkest parts of an image) available. Film has generally had more dynamic range — and the human eye is even better.

HDR imaging is one solution to this. Using the same limited hardware, several bracketing exposures of a scene are taken — some at low brightness, some normal, and some with high brightness. Parts of each image will still be clipped: the lump of coal in the above example will probably be shown as absolutely black at the dim exposure, but will show up nicely on the bright exposure. The reverse would be true for the lightbulb: it would show up nicely on the dim exposure, but would be washed out on the bright setting.

Once a series of bracketing exposures has been made, an HDR algorithm can digitally combine them into a single image with higher dynamic range. Think of it as measuring a diverse group of people with a few rulers on a wall: you can measure kids with a ruler that goes from 0.5m to 1.5m, and the adults with another that goes from 1m to 2m. You would get the same resolution at a wider range, even though some processing is needed to make the final tally.

Here is an example of HDR imaging in action, including three automatically-taken standard bracketing images and the final result. (Although the images show the effect of HDR, they are otherwise not the best possible, since they were taken using a cell phone camera with no specialized equipment.)

 

Dim exposure (-2.0EV). The sky looks great, but details on the bridge and streets below are too dark to see clearly. (Click for larger.)
Normal exposure (+0.0EV).  Darker parts of the sky, and the Philly skyline, look okay, but part of the sky is washed out and the scene below is still very dark. (Click for larger.)
Bright exposure (+2.0EV).  The city street below the bridge is more visible, but the sky is too bright to see the details of the sunset. (Click for larger.)
The final HDR image. Although not enough light was really available for this image, more details can be seen in nearly all of the image than in any of the originals — from the dark street to the bright sky. (Click for larger.)

(The pictures were taken on a recent walk across the Ben Franklin bridge and back.)

Here is another example of HDR imaging, taken on the same walk across the bridge. (I didn’t collect the originals for this one, so it doesn’t really make as good an example, even though the image itself is somewhat nicer.)

Another HDR example. Note the details in both the bright sky and darker cityscape below. (Click for larger.)

Posted in Digital | Leave a comment

All Norton’s Horses And All Norton’s Men…

Posted on 2011-08-01 by M. Eric Carr

…couldn’t put this drive back together again.

Recently, one of the HP workstations in the lab refused to boot. We narrowed the problem down to the hard drive (never a good thing). The drive had completely failed; even our hardware duplicator couldn’t do anything with it.

Usually, when a hard drive fails, there’s very little that can be done, unless you have very specialized equipment (including a cleanroom or at least a filtered flow hood) and expertise. However, I’d heard stories of people having success carefully unsticking an errant read head and bringing drives back to life long enough to recover some data, so I figured I’d see what was going on. (Don’t try this at home, folks; this drive was headed for the Dumpster anyway.) Here’s what I found:

The dead drive.

First step: Remove the screws...

...including the hidden one under the label. (The warranty had long since expired, anyway.)

Uh, oh -- that's not good. (That large scratch in the middle of the platter should not be there.) Well, we can stop being careful, now. Note the properly-parked drive heads acting as if nothing is wrong...

We have the culprit! (Head crash while in the middle of the platter. The head was found parked, as shown in the last picture; I moved it here to try to see what parts hit.)

All of the platters were affected.

This is why they're called "voice coil" drives; the heads are moved by an electromagnet, similar to the coil on a speaker. Much faster than the old way, which used a stepper motor.

The Read/Write heads, without the platters installed.

Posted in Digital, System Administration | Leave a comment

Craftmanship in Engineering

Posted on 2011-07-30 by M. Eric Carr

There’s Hacking, then there’s Engineering, then there’s “Doing It Right.” For me, Doing It Right is always something to aspire to, even if I don’t always have the time, tools, or expertise.

Recently, my granddad (94 years old today and one of the most inspiring people I know) gave me a notebook that he had kept roughly sixty years ago, while working for Capital Airlines (later part of United Airlines.) It’s full of great information and fascinating details about 1950s airliner technology — Lockheed Constellations and Douglas DC-4s, including details on specific aircraft owned by Capital Airlines. I’m working on scanning it in, and will post the whole book on this site when done, since he was kind enough to give me his permission.

An unassuming notebook, but one filled with information!

 

Talking with my granddad about engineering topics — anything from multi-row propliner engines to repairing an AC blower in a Chevy van — has always been inspiring. Here is a guy who dedicated his career to Doing It Right. (How many people not only follow the proper maintenance procedures for their lawn mower and generator, but keep detailed records of the work done on a clipboard in the shed?) I’m still learning from his example.

Here are a few of the highlights I’ve found so far while going through the notebook. (I’m working on uploading higher-resolution versions.)

Apparently there's OK-overspeed and too-fast-overspeed.

 

Magneto troubleshooting procedure. #16 cylinder will be the first to misfire.

 

Sometimes a fuel leak is OK, and sometimes it's not. Here's how you tell.

 

Ferrying a Lockheed Constellation with the nose gear doors removed. Buffeting was experienced until the flaps were lowered (which would put the plane in a more nose-down attitude.) That must have been quite an adventure!

 

A hand-drawn valve diagram. Artistry was the AutoCAD of the day!

 

Qualified to service Lockheed Constellation aircraft!

Happy birthday, Granddad — and thanks for being such a great role model for several generations of engineers!

Posted in Aviation, Nostalgia | Tagged , , , , , , , , | 2 Comments