Tag Archives: digital

Please continue to hold while I sort this thing out

Remember how mechanical clocks are prone to lose time? It’s because they’re made out of physical machinery—pendulums or mainsprings and gears. We replaced those mechanical parts with a quartz crystal, zapped it with electricity to make it vibrate and got digital clocks. Digital clocks are more reliable, but they still lose 15 seconds every month.

To make the even-more-reliable atomic clock, we replaced the quartz crystal with atoms. Atoms vibrate on their own. We’re building a clock that’s as free of physical, mechanical parts as we can manage in this bad old fallen world.

Here’s what I’m getting from my exhaustive research so far: somehow cesium atoms are funneled down a tube. How do they get the atoms out of the cesium? I don’t know. The atoms are exposed to radiation—radio microwaves like the kind you use to heat up your old cold French fries—which makes them switch back and forth between energy states. The idea is to tune the radio waves to sync up with the atom’s own vibrations at 9,192,631,770 times every second. It’s not easy to get this exactly right—like tuning in a jazz station from 2 counties over on an old radio with dials. There’s a detector at the end of the tube. When the radio waves are at the exact right frequency (the same frequency as the atoms’ vibrations), the atoms change energy states and bounce off the detector—which means one second has passed. Then what? I dunno. How does the detector know when the atoms change from State B back to State A ? I dunno.

Back to my research. Thanks for your patience. Please continue to hold.

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32,768 oscillations per second

When you hit a tuning fork against something it vibrates, giving a specific musical note.

We learned that a digital clock is regulated by measuring how many times a quartz crystal oscillates per second—32,768 times. How does it count all those vibrations so quickly? Here’s how: the crystal is purposely cut with a laser to exactly the size and shape (the shape of a tuning fork) that will produce 32,768 oscillations in a second, then stop.* The electric circuit zaps the crystal with electricity, which makes the crystal vibrate until it returns to its original shape. When the vibrating stops, exactly one second has passed. The stopped vibrations trigger the circuit to move the second hand and give the crystal another zap.

The same principle applies in animated entertainment for children. The mouse hits the cat, who oscillates for a second, then resumes his former shape.

Here’s how a tuning fork works: https://www.youtube.com/watch?v=hW-igtIn3A8

Basics of LC oscillators and their measurement


https://en.wikipedia.org/wiki/Crystal_oscillator

* “Because 32768Hz can be so conveniently divided to give a 1 second pulse, it is a very popular size for it to be cut to. Manufacturers can bang them out and be sure they will sell.” https://www.quora.com/Why-does-Quartz-vibrate-exactly-32768-2-15-times-per-second

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The liquid crystal display explained!

Three inventions moved clocks and watches away from being mechanical/analogue so they could become digital: The quartz crystal, the circuit board and the liquid crystal display.

Okay, I sort of explained how a battery works. I kind of explained how a quartz crystal works. The circuit board was easy—even a shmo like me can explain printed metallic ink on a plastic card. But—liquid crystal display? I started this post about 17 times and kept getting lost in the weeds with carrot juice and double melting points and twisted nematics and polarization…

Let’s start here: analogue clocks and watches were inaccurate because they have physical, mechanical moving parts. So we replaced the wound-up mainspring with a battery. We replaced the balance wheel with a vibrating quartz crystal. Now we need to replace the moving mechanical gears, hour-hand and minute-hand with a digital (just the numbers) display of the correct time. How do we do that?

A digital wristwatch made by the Japanese company Casio.

Instead of mechanical gears and hands, we’re going to use electricity and light.

We want a watch-face that will light up and show us what time it is. We want most of the face to light up except the numbers, which should be black so we can read ‘em easily. We’ll block the light in the shape of each number so it shows up black. The numbers will change every minute, so we need a way to change the blocked areas every minute.

In order to block the light, we need a filter. The filter lets us control which rays of light pass through and which rays get blocked. A filter could be a wall of liquid filled with crystals that all face the same direction. The lined-up crystals let the light pass through. We’ll sandwich this wall between 2 plates of glass. The crystals still let light pass through—until we zap them with a little electricity. The electricity upsets the crystals so they don’t line up anymore and light can’t pass through.

We’re only going to zap in certain areas. We want those certain areas to be shaped like numbers. For instance, when we zap the glass in the shape of a ‘3,’ those crystals in the 3-shape get upset and don’t line up with the rest of the crystals in the wall. Light can’t pass through the 3-shape, so we see a black ‘3’ on a lighted watch-face.

Just like on a circuit board, we’ll print the numbers onto the glass in ink. This ink is transparent—and it conducts electricity. Each number is designed as a 7-segment figure, so we can zap only the segments that form a ‘3,’ or whichever number we want. Each segment is wired to the battery.

This is the principle behind LCDs. It’s a simplification. I left out a lot of stuff. But you get the idea, right?


https://electronics.howstuffworks.com/lcd.htm
https://electronics.howstuffworks.com/gadgets/clocks-watches/difference-between-quartz-and-liquid-crystal2.htm
http://www.madehow.com/Volume-1/Liquid-Crystal-Display-LCD.html

Many thanks to a couple of the Western Civ Irregulars, Diana (Ms Physics) and engineering-wiz Don M—both pals of mine since childhood. They pointed me in the right direction when I couldn’t find a way to explain this one.

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Circuit boards

Three inventions moved clocks and watches away from being mechanical/analogue so they could become digital: The quartz crystal, the circuit board and the liquid crystal display.

This will look better when I paint it. For one thing, the board will be a lovely green. The bigger, more complicated circuit boards look like city maps.

If you’ve ever wired something—like a lamp—you’ll remember getting out the needle-nose pliers and wire-cutters, maybe a razor blade to strip the insulation off the wire ends; you wrap the exposed copper wire around the appropriate screws then tighten ‘em up so the wire stays put…I’m trying to imagine how you would wire something as minuscule as the insides of a watch. Wires would need to go from the battery to the quartz crystal, back to the battery with a detour to power the hour, minute & second hands after counting how many oscillations the crystal made.

The circuit board is a flat card made of plastic or resin. Instead of wires, circuitry is printed right onto the card in metal ink. A circuit board can get a complicated electric network crammed onto a very small area. A small circuit board in a watch can direct electric power from a battery to the quartz crystal and anything else inside the watch .

You can see the circuit board at 27:20 https://www.youtube.com/watch?v=SFiq8WDx5Is

The History of Circuit Boards


https://www.pcb-solutions.com/pcb-market-monitor/the-history-of-pcb-infographic/
Those old discarded mass-produced watches and circuit boards can become playthings for someone with electrical knowledge—http://www.angelfire.com/ut/horology/quartz.html
https://sound-au.com/clocks/timebase.html

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Quartz crystal

Three inventions moved clocks and watches away from being mechanical/analogue so they could become digital: The quartz crystal, the circuit board and the liquid crystal display.

Quartz is a common mineral that does this weird thing: it generates a tiny bit of electricity if it’s squeezed, and vibrates when you send an electric charge through it. Watchmakers cut quartz into a shape that looks like a tuning fork, so it vibrates like a tuning fork.

So if we just squeeze the quartz—I’m not sure if this is really the way it happens…

…wow! It works! (photo credit: KTUL.com)

Amazing!! (photo credit: Google Earth)

Okay, okay, that was just a gag. You knew that, right? Just a teeny tiny electrical charge passes through the quartz crystal to regulate the watch.

“Inside a quartz clock or watch, the battery sends electricity to the quartz crystal through an electronic circuit. The quartz crystal oscillates (vibrates back and forth) at a precise frequency: exactly 32,768 times each second. The circuit counts the number of vibrations and uses them to generate regular electric pulses, one per second. These pulses can either power an LCD display (showing the time numerically) or they can drive a small electric motor (a tiny stepping motor, in fact), turning gear wheels that spin the clock’s second, minute, and hour hands.” https://www.explainthatstuff.com/quartzclockwatch.html

https://electronics.howstuffworks.com/gadgets/clocks-watches/digital-clock2.html

A Short History of Digital Clocks and Watches

https://h2g2.com/edited_entry/A1006534

A Brief History of the Wristwatch – Part 1

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