My first integrated circuit is the 555 timer chip mentioned y’day. Not surprisingly, there is a ton of disinformation on the Internet. I’ve seen expensive, well-known outfits who post diagrams with missing wires and components. The tendency of mass communication is to even out the world’s IQ, a sad event for humanity. I’ve already discussed how the Internet has removed a lot of the shame from being professionally wrong.
Despite the UMP, the United Morons of the Planet, I’ve learned enough that the age of the unknown IC is fast dwindling. I’ve investigated only three chips so far, two of which I’ve never seen in real life. But shown here I have a working 555 timer circuit on my desk right now that is flashing a light, and I did so without any fancy calculations. [Author’s note: This "non-usage" of formulas is important to me, for as a legacy of my upbringing I missed much of the practical side of things. I can grasp all manner of complicated theory but not build anything with it. You see, a theory is safe inside one’s head, but anything you build can be “shared”, meaning broken, stolen, criticized, sabotaged, and argued as proof one hasn’t have enough grunt work to do. In such a situation, one builds very little.]
The flashing rate of my LED is determined by the combined values of a resistor and capacitor. I’ve learned to put in the capacitor first and vary the resistor, as only a few values of capacitor are commonly available. I can set the mark time, but not the space time (you can look up those meanings). My LED does not flash on instantly, but glows in stages. All pins of the LED must be tied to voltage or ground even if not used in a given circuit. The learning experience left me enthusiastic.
The significance of a 555 in robotics is that it can produce PWM, pulse width modulation. There is a difficulty controlling the speed of DC motors. The accepted method is PWM and a 555 fits the bill. The output of the 555 is an on/off digital signal where I need only figure out how to mechanically control the mark and space. I know of one other way to PWM that works superfine, but it costs a lot of money: the Arduino. (The difference is 39 cents versus 30 dollars.)
The said calculation turns out to be surprisingly easy, but there is always a tradeoff in accuracy using passive (mechanical) components. For example, the closest I can get to 1 second total cycle is 0.9773 seconds with 2x100KΩ resistors and a 4.7µF capacitor, and it is not a 50/50 cycle. More like 66/37. My old science degree, which I never used, is again becoming handy to understand units of micro, milli, pico, and nano. This is because the equations can lead to ridiculous answers such as 2 billion femtoseconds, although I admit I was playing “what if” on that one.
Don’t you hate sites that take you to their home page when you do a search on a specific item? I do. Yes, I know how hard it is to program a link to every item on a site, but once you’ve built the page, why not add the little bit of extra code? It takes too long to figure out how each business categorizes things. Do I want parts, sales, customer service, store locations or index? When I’m looking for one item and I get this type of home page, I usually just close without bothering. Did you get my drift, Meccano?
And here’s a strange one. The catch phrase I’ve used in my profile for years shows up as unique on the Internet. “They never fall who never climb.” Try it. My point is, I did not write that. I distinctly remember hearing it years ago and adopting it. When I went to locate the author, all I get is my own words back. I tried all the major search engines. Even if I’m first to publish it, I did not create it.
Later, we record an extremely successful club meeting. The 555 chip is now familiar territory. We are unable to find sources for the next two chips we wish to analyze, the 4011 and the 4017. We still do not have any books or research material other than what is on-line.
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