One year ago today: October 23, 2016, a 100 miles above Giza.
Five years ago today: October 23, 2012, family photo.
Nine years ago today: October 23, 2008, the famous Nigerian check.
Random years ago today: October 23, 2006, an obvious calendar entry.
Ah, retirement, when you can sleep in without feeling guilty. I mulled over the Maker Faire show and in the final analysis, it was excellent entertainment for the money. It restoked my interest concerning integrated circuits and made me decide to ramp up my own internal references. I’ve been mentioning how so many of my Yesteryear link-backs tend to fall on anniversaries of some kind, so why not incorporate them a regular feature? This is not so clear-cut as it seems, since this blog has a polite aversion to forward links. What I said in 2003 stays in 2003.
I used to give training talks about PWM at the NOVA meetups. I was the expert on it. Not no more. There are copious articles everywhere and I’ve lost any lead I had. Mind you, they still program funny and are often lost without downloading a library. Remember, we saw this phenomenon first day at NOVA. When given tasks, I would begin writing the software while other began searching on-line for a downloadable version.
The show vaults my robotics hobby back into focus. I’ve spent so much time without a proper lab or workstation that I’ve fallen behind. My hobby-interest leans more toward making small items that work, but with a design that allows them to be connected in a modular fashion. I stumbled on a description of the old 7289 chip and it was a shock to me how long ago I paused that project. By now, I should have a dozen of those cascaded together in some fancy display that I deserved a booth at that fair. It ain’t over yet, but darn rights I’m disappointed.
I’ll never be the scientist on the leading edge. That doesn’t mean I can’t design new things just as well as the rank and file of that fancy show. Look at this photo and now recall the ROM model that I built, the one that used clothespins a pushbuttons to illuminate an analog numeric display. That was a fussy arrangement. See how this photo uses hacksaw blades as springs? I, ahem, happen to have a lot of broken band saw and hacksaw blades. Can you see them? I kept them as handy serrated edges only to see the genius of this design at the Maker show.
Rarest US bill.
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Allow me to point out why my approach is different. The fair was full of lovely devices that had one thing in common. They were standalone. Back when I first studied computers so long ago, I developed a strong concept of re-usability. Whenever you design something, spend a while making sure it can be used as part of a larger project. Hey, this was a big leap for a 17-year-old; it was an early concept of modular components. I did not encounter anything modular until some 12 years later at the phone company. Nowadays, I think modular on every project.
Those 3D printers, I’ll guess a good 15 were in operation, were all old school. The concepts were same as the early models and according to the operators had the same problems. Clogged nozzles, lack of repair service, and lifting from the base-plate. Go look that up yourself. This month’s PopSci had an article about how some kind of mold could now produce vinyl records. Who’s the smart cookie came up with that one. Alas, the 3D printer that can do that carries a price tag of nearly $200,000 (see photo). Hmmm, how long before that capability drops to my level—less than $500. I’m stressing here that this idea of vinyl albums is my opinion of good thinking on somebody’s part.
Myself, my inventiveness is confined to what I know. I’m figuring out if an old telephone touch pad can be converted to a cheap input device. I’d like to build from scratch a ‘computer’ able to add two small numbers, that’s the 7489 chip again. There were two working DIY computers at the fair and I admire the effort. However, both smacked of replicas by lacking that confused disarray of wiring that accompanies any truly original project. One computer did nothing but count to 255/0 with a card saying it could do more. When? Next year this time? The other was a group of breadboards with small banks of chips kind of lashed together. It was adding numbers, but the output was a row of LEDs, which most people can’t read.
Hark back to my 27-LED ROM display. That has a tier of inputs that could easily display a decimal digit. Sure, one digit, but even that digit was superior to a digital output because it is user-friendly. That’s what I mean about modular. Almost every circuit board I built myself is inter-connectable. Give me a lab and watch me go at it. I’ve already designed and/or built logic gates, power supplies, latching circuits, and that all important ROM. I read a passage about programmable ROM. It uses the same wire grid logic I inferred on my own. It has a superior method of “write once”. My solution was to simply not solder any diodes where I didn’t want them.
This other ROM (alas, I did not download the article) used the nifty method of connecting every node with a fuse. The idea was to program the ROM one-time by applying commands that burned the fuses where they were not desired. The result was an easy and cheap ROM chip. Pardon my lack of knowing this stuff by now. Nobody told me. That’s why I yearn for a lab where I can test these ideas. I remain staggered at the tackle available at the high school level at that convention. Each team of semi-attention-paying students had more apparatus on their work bench than I spent on this house.
“Well I have to say,
you’re not laughing now, are you?”
~Nigel Farage.
Non-computer visitors can skip this next section. Turning away from the Arduino, I’ve decided to resurrect the 7489 project with a better modular design. The original, which is in the shed somewhere, had duplicate pins to make it compatible with clocked input, something I still don’t understand all that well. The chip is random access memory that can store up to 16 numbers that are each 4 bits long, that is, digital numbers between 0 and 7. This is purely a learning design intended to find out the operational characteristics not covered by the instructions.
I’ve built banks of working relays for the cPod and I find a certain charm to listening to them operate. I enjoyed slowing the relays down so the observer could follow the pattern of events. I tried and failed to make them [relays] into a memory circuit, but succeeded in getting them to emulate gates. That was an early breakthrough for me, discovering that to make the relays work, they had to be wired so as to become self-latching, that is, when they turned on, they stayed on until another command released them. Not one of the textbooks said a peep about that.
So again I’m thinking. If I can make gates, I can make adders. If I can make adders, I can perform all basic arithmetic functions. This is the basis of my ho-ho claim that, if I had to, I can make a computer out of discrete parts. Discrete is the electronics adjective for ordinary small passive parts, like resistors and capacitors. It more specifically means not using any integrated chips. Yes, the 7489 is a chip, but I won’t go past it until I learn its every last quirk. It is my belief that nothing new will come of electronics without reinventing the wheel. What I saw at the show was not creative at that level.
That’s the same situation I encountered earlier. It is so tempting to plug pieces together empirically and see what works. To heck with the formulas. I’m still like that but now I have a feel for what parts work well together. And I definitely understand the ways electricity recreates logic. That’s how I became interested in building my own gates and memory which many would say is a backward study step. But I can’t help it if I find that part the more interesting.
At the show, I talked with the guy who built a wooden pipe organ. It was nice but had been done before, so my curiosity was the cost. He rapidly pointed at the solenoids and said that was the part that hurt. The organ had a bank of them, one for each key, and he said even buying them in bulk, they worked out to $3 and $4 apiece. The rest of the instrument was mostly wood, the same medium I chose, once again, due to the expense of working with anything else. Anyone who thinks even plastic is cheap is talking about the quality, not the price.
Still, I thought, $4 per solenoid is a lot less than $15 for a relay, remember the Taurus. And they both work on the same principle. By the end of this day, I’ll have some concept together on how they could be used to create logic gates. I’ll look on-line but I don’t recall ever having seen a working model, though I have watched that nifty video of the relay-based 8-bit computer, oh, what was it called? Anyway, kids, if you want an appreciation of how a modern computer works with millions of logic circuits, try building just one gate by yourself.
And don’t give up. I never began to look at circuits until I was out of school over 35 years. My advice is the same: beginners read many authors before you commence, because every author I’ve ever read in this field is a bit of an idiot in his own way. The classic example is whether the transistor is a switch or an amplifier. An idiot won’t give you a straight answer. I will. It is both. It depends on whether the input signal, a.k.a. the base current, is digital, which makes it a switch, or biased analog, which makes it an amplifier. Eighty dollars please.
ADDENDUM
Walnuts. Particularly black walnuts. I learned these are very difficult to package and preserve. Apparently they don’t keep, even in expensive containers that are okay for other nuts. The shelf life of the best is six months and that makes me remember some of the baking items in my pantry are approaching two years old. Time for a review. But I kept walnuts in my emergency rations and honestly, I never detected any difference or staleness to the flavor in all that time. The more likely explanation is that a lot of us just got used to the taste of stale walnuts. And instant mashed potato. Don’t forget instant mashed potato. RofR, my former business partner, hated walnuts.
And before I let you go, let me give a definition of what I consider an idiot in the electronics field. That’s a man, always a man, who will never admit he doesn’t know something unless it is to get himself out of doing some work. Now, now, that is purely a fluke that I just described my brothers. And settled in back at home, I wish I had taken the batbike to the exhibition. Alas, no more motorcycling until I get the go-ahead from my people.
Last Laugh
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