Remembering Challenger

January 28, 1986 was not a good day for engineering.

Thirty years ago today, NASA management let politics and administrative expediency take priority over engineering and safety. Seven astronauts — seven of literally the best and brightest among us — lost their lives because of a hasty decision to go ahead with the launch despite the protests of engineers that the weather was too cold for the o-rings in the solid rocket boosters.

The astronauts were not our only loss, that day. We lost an extremely expensive orbiter, too — but perhaps an equally large tragedy was the extent to which the Challenger disaster set back humanity’s exploration of space. Because of a rushed management decision, the Space Shuttle program — and piloted spaceflight in general — suffered a delay of perhaps a decade. Many dreams, and many STS flights, were cancelled or greatly delayed.

What’s done is done — but the best way to honor the memory of the Challenger Seven is for us to learn from the management mistake that doomed them. Yes, NASA fixed the SRB design and used improved o-rings, but that’s not the real point.

The important lesson is that we must never let wishful thinking and politics override solid safety engineering practices. We’re competent enough with physics to know the risks in many situations, if we’re only patient enough to do the calculations — and accept the logical conclusions, even if they’re not the ones we want to hear.

“For a successful technology, reality must take precedence over public relations — for Nature cannot be fooled.”

–Richard Feynman


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Electronics Intuition, or The Giggle Test

Mathematical analysis is one of the most useful tools in electronics. With the right formulas, you can figure out what value capacitors and inductors to use to make a resonant circuit operate at a particular frequency, or what resistors to use to make a voltage divider to drive a comparator.

Along with working the equations, though, it’s important to have a good intuitive sense of what is going on in a circuit. Just like you shouldn’t trust your calculator if it gives you an answer of 21 if you ask it for the product of 17 and 38, you should have a reasonable idea of what each of the parts of a circuit are supposed to be doing, when you’re analyzing it.

For example, if your calculations indicate that you’re getting 100 amps out of a signal generator, something has gone wrong. That kind of current would melt the coax cable — let alone the sensitive components inside a precision signal generator. Likewise, if the calculated output voltage of a simple voltage divider circuit is higher than its input, something has gone wrong somewhere. Resistors can’t generate increases in voltage.

Similarly, some ideas just aren’t feasible. Over-unity (“free energy”) devices are the most egregious example — but often, devices like energy harvesters which look more or less plausible haven’t been properly quantified, in terms of energy out vs. energy in. Just because something can generate high voltage, for example, doesn’t mean there’s a lot of energy there. Quantify, in SI units, the inputs and outputs — and then measure them.

My favorite term for this way of thinking is “The Giggle Test.” If an engineering idea is so implausible that you have to suppress a giggle (or fail to suppress one), something’s wrong — and probably wrong by at least an order of magnitude. When you see something that doesn’t make sense, there’s a reason. Take the time to look at the quantities from a larger perspective, and ask yourself if they make sense. It can be a real time-saver.

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Just the Thing

If Necessity is the mother of Invention, Laziness is its father. Lowering the barriers to innovation certainly helps encourage the development of new solutions.

One technological feat that has been getting increasingly easier to do with embedded devices is send and receive data over the Internet. The recent development of the ultra-low-cost ESP8266 WiFi module has spurred a lot of interest in getting smaller devices connected to the ‘Net. The “Internet of Things” is essentially the idea that even small, single-purpose devices might be more useful when connected to the Internet.

Unfortunately, the original ESP8266 boards weren’t the friendliest things to prototype with. Their awkward two-row connector is mechanically stronger than an inline solution — but the geometry of most breadboards means that DIL parts with less than 300mil separation can’t be easily breadboarded. Plus, the ESP8266 uses an inexpensive but obscure Cadence Tensilica processor — not supported by most enthusiasts’ toolchains. Sure would be nice if someone were to bake an ESP8266 into an Arduino and write the libraries.

Seems like SparkFun had the same idea. Their “ESP8266 Thing” is essentially a high-powered Arduino-compatible CPU attached to a ESP8266 module. With the libraries and examples provided, it’s reasonably easy to get up and running with a webserver.

The SparkFun ESP8266 Thing Dev Board

After setting up the Thing (Note: you need to short GPIO0 to ground in order to get it to program), I modified a temperature and humidity webserver from Adafruit to create a webserver that could turn on an LED when the /on page was read, and turn it off when the /off page was read. It’s straightforward enough to modify this to, for example, control A/C outlets.

Here’s the sketch.

$16 to connect a gadget to the ‘Net, almost effortlessly. I love living in the future.

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How Not To Build A Tablet PC

Just came across this video by Dave of EEVBlog (see below). Now, granted, a little Dave goes a long way — a lot of his videos consist of him ranting about how horrible some piece of tech or another is.

Dave’s ranting is 100% justified in this case. Someone custom-built a Windows XP tablet PC, and they seem to have used it as an opportunity to thumb their nose at just about every single electronics rule in the book.

The power supply board (why they would hand-roll one when they’re a commodity item is beyond me) is particularly craptastic. They went to the trouble of making a two-layer board, only to basically not use the second side. They’re also using quite a few through-hole components as surface-mount components. It’s only a matter of time until those solder joints fail and come off the board.

There are many, many other no-nos visible:

  • Cold solder joints throughout;
  • Holding boards in place with double-sided tape;
  • Soldering directly to rechargeable batteries without tabs;
  • Packaging the batteries together with shipping tape;
  • Leaving loose, unused wires in place (at least they put some shipping tape on them as a talisman to ward off electric short demons);
  • Soldering a USB cable to a board, when a USB-to-mini-USB cable would do great;
  • Using at least three different battery packs one battery pack in three pieces;
  • Using a heatsink pad in a halfhearted attempt to couple the heatsink to the case; and
  • Using a heatsink with no provision for airflow. Where’s it going to dump the heat to, guys?

Dave is known for his over-the-top rants — but he gets a pass on this one. This is weapons-grade craptastic construction. (I suspect that either the company has VERY strong micromanagement — and/or they’re using interns with almost no electronics experience.)

Yeah, it’s serial number 11 — so a few glitches are to be expected. But this thing is almost cargo-cult-like in its construction. I’m really surprised that it works. (It won’t, for long.) And this piece of crap was sent to a client. A medical facility, in fact! I wouldn’t have tried to turn this in as a class project. Its construction would be just too embarrassing. I’ve never seen any student projects anywhere near this bad. Not even from freshmen who are learning electronics for the first time. At least they have intelligence and common sense.

(Warning: this video may cause Computer Engineers to lose faith in humanity…)

Posted in Design, DoNotTryThisAtHome, Electronics, Reverse Engineering, Reviews | Leave a comment