Here’s a great quote by John Bass on an EDN article about function pointers as an implementation of state machine design:
Failure complexity is a metric of a design.
http://www.edn.com/electronics-blogs/embedded-basics/4406821/Function-pointers—Part-3–State-machines
A while ago, I modified my daughter’s little kid kitchen. In that project, I found my design self teetering on that edge between two goals: get-it-done on the one side, do-it-right on the other. I had chosen the former and even my 2 year old (at the time) could see that this was a critical design mistake.
As a quick refresher, I had thought Those Thoughts 1. “Wouldn’t it be cool if her cute little IKEA oven had a light that turned on when the cute little door was opened?” Well, yes, but perhaps it would have also been cool if I’d considered the very likely fault condition wherein my toddler would leave the door open. Toddlers do that.
And you guessed what happens next: batteries died.
A very wise engineer once told me, “Rob, there’s never enough time to do it right the first time. But there’s plenty of time to fix it later.”
Well, here I am, fixing it finally.
I knew that a timer was in order. So I blew the dust of my Forrest M. Mims III Radio Shack booklets, particularly the indispensible 555 timer book.
When I was done, this is what I cooked up:
So to explain the “truth table“, the operation works like this:
One other critical circuit requirement that the above Mims diagram does not account for was with the trigger input. His classical circuit only triggers on level changes, active low. In other words, for as long as the input is held low, the timer would be in standby.
That wouldn’t work for me, since I wanted the timer to start when the door opened. That’s an edge-sensitive requirement. I found a nice, easy capacitive switch solution:
The results, finally, were as they should have been: nice well-lit oven that doesn’t wear out the toy batteries. My engineer buddy would agree.
My garage has a single light switch in it for its overhead fluorescent lights. This light switch is not conveniently located; it is situated beyond our freezer, such that one has to walk into the darkened garage in order to turn the switch on. So I made an electronic 3-way switch. “Why?”, you ask. Indeed. My reasons are always convoluted and sometimes irrational. Best not to ask such questions.
But if you must know, our garage is mostly finished with drywall, so adding a second “3-way” switch would have been difficult. I opted for an electronic switching circuit 1.
First, start with the napkin diagram:
The core of the design revolved around a JK flip flop. Rockin’ this project with 30 year old technology.
For the mechanical switch, I removed the AC switch and used a surface-mount garage door momentary contact switch. The wiring then can also be garage door opener grade, small current wire (since this input to the circuit is on the low-voltage digital logic chip).
Here are some photos of the final project:
Full Project Album:
“Daddy, Ebenezer not sick anymore?” “No sweetie, he isn’t sick anymore.”
Ebenezer was more than just a pet cat. He was a symbol of my developing adult life. I got Ebenezer when I lived in Dallas. My Aunt Debbie and Uncle Rick knew of a neighbor who had a new litter of kittens. They knew just the animal lover that would make a good fit for one of them. I was a sucker for the little orange tom’s spunk and loud caterwauling.
That first week was a trying one, as all young animals prove to be to their human caretakers. One evening after work, he had managed to get himself completely wrapped up in small gauge solid-strand antenna wire. As I was carefully cutting him free of the snare, unwrapping the wire from his throat and body, I knew then that I loved him. I knew that he depended on me for his life and happiness. And I was glad then that I had this little creature to care for. It felt good to give joy, as well as shelter and sustenance.
In a sense, I feel Ebb was a good foreshadowing of my future family life. He gave me good training for what it means to be a dad: he was my first dependent mouth to feed.
He was also my first pal. He moved with me at least eight times (one of which was across multiple state lines!) between many apartments, townhouses, and houses. He successfully integrated well into an already bustling animal family when I married Sarah.
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I nearly lost Ebb shortly after he and I made the long trek to Colorado. He was always fond of wandering outside, and I was a pushover for his pleading. One such night, while I tinkered in my workshop, I let him have a lay of the land. I heard a slow scuffle and came running out.
I found him, caught firmly between two young coyotes. One had his tale, the other his throat. I had interrupted the fight before major blood was spilled and lucky Ebenezer held onto a couple of his remaining lives. It was such a close call; he and I learned some lessons that night.
The origin of his name was simple. I had always liked it from the Dickens story. And when Ebb was just a kitten, it was hard to see how the name could possibly fit his personality. But over the years, as he became more cranky and less mobile, he seemed to settle into his namesake. Aunt Deb sometimes mistakenly called him “Nebuchadnezzar,” which is a greater name by syllables, but a lesser by Biblical standards 1. Iris, you can imagine, had a very hard time with his name and early on became content with the shortened “Ebby.” Later, she fancied his full stately name, and it had a sweet ring to it from her mouth.
As with so many things in my life now as a father, I can’t help but see the world through my kid’s eyes. And this event was certainly no different. As I came home from the vet, with an empty carrier under my arm, Iris greeted me at the door and immediately asked:
“Daddy, Ebenezer not sick anymore?”
It’s a funny thing to experience great sadness simultaneously with happiness. I smiled behind tears and said, “No sweetie, he isn’t sick anymore.” And because Iris doesn’t yet fully grasp the sorrow of loss, she was happy for me.
Sorrowing I shall be in spirit,
Till released from flesh and sin,
Yet from what I do inherit,
Here Thy praises I’ll begin;
Here I raise my Ebenezer;
Here by Thy great help I’ve come;
And I hope, by Thy good pleasure,
Safely to arrive at home. 2
[stextbox id=’alert’ caption=’Spoilers Below’ color=’ffffff’ bgcolor=’ff0000′ bgcolorto=’ff0000′]Note that every word following this is considered a major spoiler for the film.[/stextbox]
For some reason, this keeps happening to me. I must be doing it wrong. But I’ve either been too stubborn or too distracted to find the better way to do it.
I’ve installed surround sound wiring into my abodes at least five times (twice in my bachelor days at two different apartments 1, and thrice in my married days in all three of Sarah’s and my mutual houses. So I have a fair amount of experience with fishing wires down walls and into ceiling joists, cutting in low-voltage single-gang electrical boxes, and wiring up multi-channel audio speakers.
But the one step in this many-tiered project that I haven’t mastered is this: the differentiation of the channels during the final wiring.
Here’s what I mean. You get all the four main channels mounted and wiring run from the four corners of your media room 2. Add the center channel and you have five sets of wires coming into a single hook-up junction box near your media center cabinet. Next step: terminate those 10 conductors 3 into speaker lugs, or banana jacks, or binding posts.
But which channel pair goes to which speaker location? Doh!
And it’s not just an accident. I have tried various cable labeling in the past, as I did this most recent installation. But inevitably, my installs have included fish-taping cable down finished walls 4. Therefore, the labels that I’ve used — such as tape or zip ties, etc. — have always come off the cable in the process. Without that identification, it’s hard to know how to hook the cables up.
So what to do? I haven’t found much on the DIY home audio forums on this topic, strangely, which makes me wonder if I’m going about this installation all goofy. Do the pros do it better? Probably.
My first generation surround sound amplifier had a channel test tone utility that was helpful. It would emit a 1KHz tone into each channel for about 2 seconds and automatically increment to the next channel. But this wasn’t ideal for a few reasons: 1) It wasn’t controllable. Once that 2 seconds had expired, you’d have to race to the other speaker to hear the tone. Not very efficient. 2) The tone obviously required that the speaker cable be terminated between the speaker and the amp to be of any use. It’s an audible tone, therefore you need a speaker to hear it. So that’s not too helpful either since I’d rather hook up all the wire after I determine which set of wires goes to which speaker channel.
So here’s how I solved the problem.
The nice thing about this method is that the LED is unidirectional. In other words, it doesn’t light unless (conventional) current is flowing from positive to negative. This is key, because you don’t want to get the positive and negative terminals mixed up to your speakers. Therefore, using a DC incandescent light bulb would be a mistake, since it will light bi-directionally.
I’m aware that some speaker wire have knurled, striped, or discolored conductor insulators to help you differentiate between the two. This is helpful in most cases. But in two of my installs, I used some Monster brand cable that had little to no helpful indicators. So the above bailed me out.
I love “computer” 1 programming. There are many good programming principles that can be applied to life.
Take for instance the difference between syntax and semantics in language. Syntax is the nuts and bolts. It’s the grammar, the rules that tell you how to construct a sentence correctly. Its meaning is derived solely from how the words fit together. The sentence:
Water trees from drink brook the.
…has no syntactical meaning. And yet, you and I know what that sentence is trying to convey, don’t we? That’s called semantics.
Semantic meaning is derived from the context of the sentence, based on a priori knowledge. Your life experiences, your age, your wisdom – these allow us to infer meaning to chaotic elements. We can look at the sentence above and interpret the jumbled nature to see the greater structure:
Trees drink water from the brook.
I like to think that a great many of our confusions in interacting with each other have more to do with syntactical confusion, rather than semantic. We are too focused on the trees by the brook, rather than the forest.
I caught this nice little Kickstarter video today while reviewing the top 2012 funded projects. It’s a typeface commissioned by the city of Chattanooga. Their pitch video is really well done, in that Helvetica 1, designer-friendly way. It reminds me of the really excellent podcast “99% Invisible” by Roman Mars, which explores the hidden world of design principles and how that world commingles with the public.
I’m inspired by good design, even if the design isn’t in my own field. And on top of that, I’m inspired by esthetic qualities of all design. I suppose that’s why I’m more Apple than Microsoft or Linux.
There are hunters and there are gatherers. I’m more the latter, my wife the former. I like to settle down and dig my roots in. What can I say, I don’t like change.
The same goes with my job choices. My first job post-college lasted 10+ years. It basically fell into my lap — a recently graduated upperclassman contacted me during my senior year, asking if I wanted a job. I said yes, and so did the company. MTSI was a fantastic experience for me; great people, great training, great experiences.
Then I moved on to Colorado. And what a wild, dizzying path that has become. Liteye Systems brought me here, and I am forever grateful. I found my wife here, and my life is all the richer.
Soon after Sarah and I married, we moved into our first house together in the old part of Colorado Springs. Liteye is located in Denver. The distance from point A to point B is about an hour’s worth of travel time. On good traffic days with perfect weather. It’s been a long 6 years of commuting. Again, I settled in and stayed perhaps longer than was necessary.
And so, this summer became Project Find-A-New-Job. Enter Thermo Fisher Scientific smack dab in the middle of Colorado Springs.
I had been wanting to branch out a bit from Liteye. Having been immersed in the rugged military product development world for quite a while, I wanted to see what else I could do. Thermo Fisher fit that bill. It’s in a completely different market: high-end scientific and laboratory products. It’s a branch of industry that I had no experience in, so I was excited to take part.
It’s also a very large company with a small local branch. This was something I was looking for specifically too. My previous couple job experiences ranged in the sub-50 employee size and were both startups. Though those environments can be very exhilarating and dynamic, they can also be occasionally chaotic. I was craving a larger company culture, where processes and infrastructure were more fully developed.
And what can I say about a commute of only 15 minutes? As the snow steadily fell this week, I revealed in the fact that I wasn’t stuck on I-25. Being a true “local” of the Springs now, I’m eager to settle in here and reinvest all this extra time I have on my hands into my family and friends.
The planet Pandora has nothing — and I mean nothing — on the little moon SC-223. This place scared the (R-rated expletives) out of me; it was unnerving, frightening, dreadful, in all the ways that Pandora was not.
