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After a long hiatus, I’ve finally returned. I’ve revamped my site and reposted all of the old blog posts. Some have dated links, etc, but I just posted as-is for now. And I plan to add new content soon.
If anyone is struggling with what Christmas gift to get the Mechanical Engineer in your life, look no longer. This is pure genius. I suspect most M.E.’s are like me. I’ve got a pile of gadgets and novelties on my desk that I occassionally pick up and fiddle with. But just think how much fun I, err, your Mechanical Engineer friend could have with one of these.
I was listening to the news this morning and was reminded of something I learned in the early days of my engineering education. I recall being told that somewhere in the world there is a physical bar that is 1 meter long. The purpose of this sample is to establish the standard length of a meter. A little searching on the internet corrected my memory. In actuality, in 1889 the Internation Bureau of Weights and Measures established the International Prototype Meter. It was defined as the distance between two lines on a bar composed of 90% platinum and 10% iridium when measured at the melting point of ice.
The purpose of a standard is to ensure that the definition does not deviate over time. Try this little experiment sometime. Using a tape measure, mark and cut a 10cm piece off a length of wood. Now, use that piece to mark and cut another “10cm” piece. Using this new “10cm” piece, mark and cut again. Repeat this process until you have nothing left to cut. Measure that last block of wood using the tape measure and you can see how the definition of “10cm” has evolved over time. Of course the best way to get a pile of 10cm blocks of wood is to measure, mark, and cut each one using the tape measure.
Now back to what prompted this thought process. I was listening to the news and heard of an athiest group that was threatening a lawsuit against a school district over the display of scriptural references on signs made by some students. As I began to think about this, I realized how we have deviated so far from the standard. We allow lawyers and judges to look at past cases and decisions to determine how they should decide new cases. Then they repeat this process over and over, continually getting further and further from the standard, when what they really need to do is ignore all of those previous decisions and consult the standard which, in the case of the United States, is the U.S. Constitution.
Source: Wikipedia | Amarillo Globe-News
I’m pretty sure I had ran across one of these before but was recently reintroduced. EngineerGuy (Bill Hammack) does a great job explaining how anodizing works…
Along the same lines as that last post, I saw this on someone’s Facebook page. It’s another one of those things the younger generations will not experience.
Has this ever happened to you? You see an error in a document or on a drawing and attempt to fix it, only to introduce a new error. Come on, everyone’s done it before. But I had no idea until recently there’s a name for this phenomenon: Muphry’s Law.
Notice this is not the same as Murphy’s Law. Murphy’s Law says that if anything can go wrong, it will. Muphry’s Law on the other hand basically says if you try to correct someone else’s error, you will make an error yourself. Or, in other words, it’s easier to see mistakes made by others than it is to see your own mistakes.
This is based on a Biblical concept. Matthew 7:5 says You hypocrite, first take the log out of your own eye, and then you will see clearly to take the speck out of your brother’s eye.
Source: Muphry’s Law
I ran across this blog post recently and it reminded me of something else I had observed a while back. Thought I’d share both: 11 Sounds That Your Kids Have Probably Never Heard”
I was noticing there are quite a few old school items and terminology that made their way into today’s technology, the origins of which the next generation will not understand:
- Carbon Copy – CC on an email vs the old dye coated sheet sandwiched between two sheets of paper and ran through a typewriter
- Floppy Disk – what in the world is that little save symbol on most editing tools (word processing, image editors, etc)?
- Cut-n-Paste – scissors? what does that have to do with a computer? Use to have to really cut from one piece of paper and paste/tape it onto another piece of paper
- Clipboard – that really was a place you put your work in process until you were ready to file it away in a folder, which brings up… Folders
- Clip Art – had to really clip those little pictures out of magazines and newspapers
- Filmstrip – use to be a series of still frame photos attached together
These are just a few I see in the toolbars of some readily available applications.
In a world of chaos and confusion, it is of great importance to be well grounded. This means being rooted with a strong connection to a stable foundation. Well, the same applies in the electro-mechanical world. The best laid plans can be compromised by a poor ground scheme.
Grounding sounds so simple, yet it is a very complicated thing. You get the electricity to a component or device with the proper current and voltage so everything should work as planned, right? But the problem is those electrons aren’t happy with piling up at the end of the line, they want to go home. So a return wire is required to transport them back from whence they came.
From physics we learned that a current traveling along a wire creates a magnetic field. And inversely, a changing magnetic field will cause a current in a wire. This means an induced current in a wire can adversely affect other circuits in the area by creating unwanted currents. The way to reduce the effects of all these magnetic fields is to route the return path parallel and in close proximity to the source line. This way the magnetic fields cancel each other.
In addition to these planned source voltages and currents there are several possible sources of undesirable ones. These include electrostatic discharge (ESD), radiated electro-magnetic interference (EMI) from other nearby electronic devices, and electrical short circuits due to failed insulation, cut wires, water intrusion, etc. I’m sure there are others.
For the latter, it is important to provide safety grounds from the outer chassis or any other conductive components that people can touch. If a power wire becomes disconnected or cut in an ungrounded chassis, and then falls against the chassis, the electrons will just sit there all dressed up and nowhere to go. Then along comes a technician to service the ‘dead’ device. He inserts his screw driver to remove the access panel and then he is reminded of how much he despises incompetent engineers. Safety ground connections provide a path for these undesirables to go home through a low resistance path so they are less likely to go home thru human flesh.
ESD & EMI are similar in some respects. They are not a safety hazard to the operator or technician, but they can negatively affect the function of the device and in the case of ESD, it can be destructive as well.
To protect electronics from EMI, it is best to surround them in a Faraday cage. If you want to learn more, I recommend this video from MIT physics professor Walter Lewin. The concept is to provide a layer of skin that causes the induced currents to seek their ride home on the outer shell of the enclosure and never make there way to the electronics inside.
To protect against ESD damage, it is important to ensure all conductive parts are grounded and plastics are of a static dissipative type. This will prevent ESD buildup on these parts which will eventually seek ground by arcing. Often this arc occurs in the least preferred location such as thru an expensive processor chip to a nearby mounting screw on a PCB. It is also important to provide a ground path for service technicians to dissipate any ESD they are carrying around prior to touching the innards of the device.
Now for the rub. There are just about as many grounding schemes as there are grounding concerns. Grounding terminology includes things like Isolated Ground Zone, Integrated Ground Plane, Single Point Ground, Ground Window, Star Point Grounding, etc. These different terms and approaches all have there place. But they are all intended to manage the ride home for all of these pesky little electrons in a controlled way while taking into account ground loops, magnetic fields, safety, and one more big one – surges due to things like lightning strikes. I didn’t even plan to bring this one up because it kind of turns everything upside down. A lightning strike can raise the voltage potential of the earth resulting in your ground currents wanting to reverse course and go the other direction which means your nice connection to what was once a stable foundation is no longer very stable.
For some additional reading on grounding, take a look at these:
To Patent or Not to Patent – After 20+ years of mechanical design in a high-tech industry, I look back and wonder why my name is not found on a patent somewhere. I’ve worked with many others who have had various designs patented, but every one of them I can recall just didn’t seem patentable. They appeared to be simple solutions to design tasks that were not overly creative or revolutionary. They were typically just a variation of an existing latch, hinge, or cable routing bar. Something so simple can’t possibly be patent worthy, but somehow they did it. The common thread in all of these instances is the patent process was pursued by the company and not by the individual. As you know there are many companies who get ‘patent happy’ and try to augment revenue by defending their patents.
I’ve considered pursuing patents as an individual on a few occassions but, as I’ve noted before, my hesitation usually results in watching my idea come to market without me. This has been a little disheartening. Now, having read ‘the ugly truth’, I am re-energized and optomistic about that idea I’ve been sitting on. Why not just move forward with the design and manufacturing? Why not make a few bucks now before the big guys come in and monopolize the market. It may not turn into that ‘million dollar’ idea, but as long as it’s cash flow positive, what harm is there?
Reference: A Better Mousetrap