Quick quiz: How many ESP8266 modules do you need to make an LED clock? Hint: a clock displays 12 hours.
Nope! Twelve is not the answer. But that didn’t stop Hackaday.io user [tamberg] from building a 12-ESP clock during the Bilbao, Spain Maker Faire. The “advantage” of using so many ESP8266s is that each one can independently control one hour LED and its associated slice of five minute-marker LEDs. Each ESP fetches the time over the Internet, but only lights up when it’s time.
It’s like parallel processing or something. Or maybe it’s redundant and failsafe. Or maybe it’s just an attempt to put the maximum Internet into one Thing. Maybe they had a team of twelve people and wanted to split up the load evenly. (We couldn’t think of a real reason you’d want to do this.)
All snark aside, the project looks great as you can see in this Flickr gallery, and all of the design files are available if you’d like to re-use any parts of this project. We’re thinking that the clock face is pretty cool.
[Scott] doesn’t have any kids, but he’s the sort of type that likes to get ahead of the game. Of course this means spending time in his garage to build a rocking cradle. Usually, these are acquired from a baby shower and are powered by batteries. Terribly uncool, considering a mechanism to keep a pendulum swinging has existed for hundreds of years now. His latest project is the escapement cradle – a cradle (or hammock) that keeps rocking with the help of falling weights.
The first video in this series goes over the inspiration and the math behind determining how much energy it will take to maintain a swinging pendulum. The second video goes over a very rough prototype for the escapement mechanism with some woodworking that looks dangerous but is kept well under control. The third video puts everything together, rocking a cradle for about 10 minutes for every time the weight is lifted to the top.
Even in the face of an Internet of Things grasping for a useful use case, an Internet-connected clock is actually a great idea. With a cheap WiFi module and a connection to an NTP server, any clock can become an atomic clock. [Jim] decided to experiment with the ESP8266 to turn a cheap analog clock into something that will display network time using a bunch of gears and motors.
The clock [Jim] chose for this build is an extremely cheap clock pulled right from the shelves of WalMart. This clock uses a standard quartz clock mechanism, powered by a single AA cell. The coils in these quartz movements can be easily controlled by pulsing current through them, and with a few a few transistors and diodes set up in an h-bridge, an ESP8266 is quite good at setting the time on this clock.
The software for this clock first connects to the WiFi network, then checks an NTP server for the true time. Once the ESP8266 gets the time, it starts hammering the coil in the clock movement until the hands are where they should be.
[Jim] says the project needs a bit of work – there is no feedback on the clock to determine the position of the hands. Instead, the time is just set assuming the clock hands started off at 12:00. Still, even with that small fault, it’s a great build and a great exploit of what can be done with a cheap quarts clock movement.
Play the demo video below and try not to let the rhythm worm its way into your brain. What you’re hearing is the sound of a bunch of clocks, amplified. None of them are keeping wall time, but all of them are playing together.
The video looks like eight identical version of the same module. The input takes a voltage and converts the rising and falling edges into pulses to drive the coil of an el-cheapo clock. The LEDs pulse as the poles of the clock switch to the incoming beats. The output comes from an amplified piezo sensor stuck on the back of each clock. That is, what you’re hearing is each clock ticking, but amplified. And if you watch the dials spin, it doesn’t look like any of them are telling time.
So far so good, and it matches up with the schematic. But what’s up with that switch on the front? It doesn’t show up anywhere.
And what’s driving the show? [Gijs] tantalizes us with a master clock module (on the same page) that looks like it does keep time, and outputs subdivisions thereof. But that would be too slow to be what’s used in the video. Has he swapped the crystal to make it run faster? It’s a mystery.
Word clocks are pretty popular “artsy” ways of telling time, but [doktorinjh] wanted to try something a little different. So instead of showing the time — it shows the weather.
He’s using an Arduino Yun to access the Weather Underground API for data and then sends the data out to a grid of 100 individually addressable RGB LEDs — NeoPixels to be precise. The LEDs are overlayed with a laser cut acrylic sheet with various words and weather icons to allow for a pretty specific depiction of current (or future) weather conditions.
The frame is made out of colonial style molding and since it’s a weather clock, he turned the grid of LEDs into a rainbow effect, because, why not?
Until the 1960s, watches and clocks of all kinds kept track of time with mechanical devices. Springs, pendulums, gears, oils, and a whole host of other components had to work together to keep accurate time. The invention of the crystal oscillator changed all of that, making watches and clocks not only cheaper, but (in general) far more accurate. It’s not quite as easy to see them in action, however, unless you’re [noq2] and you have a set of strobe lights.
[noq2] used a Rigol DG4062 function generator and a Cree power LED as a high-frequency strobe light to “slow down” the crystal oscillators from two watches. The first one he filmed was an Accutron “tuning fork” movement and the second one is a generic 32,768 Hz quartz resonator which is used in a large amount of watches. After removing the casings and powering the resonators up, [noq2] tuned in his strobe light setup to be able to film the vibrations of the oscillators.
It’s pretty interesting to see this in action. Usually a timekeeping element like this, whether in a watch or a RTC, is a “black box” of sorts that is easily taken for granted. Especially since these devices revolutionized the watchmaking industry (and a few other industries as well), it’s well worthwhile to take a look inside and see how they work. They’re used in more than just watches, too. Want to go down the rabbit hole on this topic? Check out the History of Oscillators. Continue reading “Strobe Light Slows Down Time”→
The laptop I’m using, found for 50 bucks in the junk bins of Akihabara has a CPU that runs at 2.53GHz. Two billion five hundred and thirty million times every second electrons systematically briefly pulse. To the human mind this is unimaginable, yet two hundred years ago humanity had no knowledge of electrical oscillations at all.
There were clear natural sources of oscillation of course, the sun perhaps the clearest of all. The Pythagoreans first proposed that the earth’s rotation caused the suns daily cycle. Their system was more esoteric and complex than the truth as we now know it and included a postulated Counter-Earth, lying unseen behind a central fire. Regardless of the errors their theory contained, a central link was made between rotation and oscillation.
And rotational motion was exploited in early electrical oscillators. Both alternators, similar to those in use today, and more esoteric devices like the interrupter. Developed by Charles Page in 1838, the interrupter used rocking or rotational motion to dip a wire into a mercury bath periodically breaking a circuit to produce a simple oscillation.
As we progressed toward industrial electrical generators, alternating current became common. But higher and higher frequencies were also required for radio transmitters. The first transmitters had used spark gaps. These simple transmitters used a DC supply to charge a capacitor until it reached the breakdown voltage of the gap between two pieces of wire. The electricity then ionized the air molecules in the gap. Thus allowing current to flow, quickly discharging the capacitor. The capacitor charged again, allowing the process to repeat.
As you can see and hear in the video above spark gaps produce a noisy, far from sinusoidal output. So for more efficient oscillations, engineers again resorted to rotation.
The Alexanderson alternator uses a wheel on which hundreds of slots are cut. This wheel is placed between two coils. One coil, powered by a direct current, produces a magnetic field inducing a current in the second. The slotted disc, periodically cutting this field, produces an alternating current. Alexanderson alternators were used to generate frequencies of 15 to 30 KHz, mostly for naval applications. Amazingly one Alexanderson alternator remained in service until 1996, and is still kept in working condition.
A similar principal was used in the Hammond organ. You may not know the name, but you’ll recognize the sound of this early electronic instrument:
The Hammond organ used a series of tone wheels and pickups. The pickups consist of a coil and magnet. In order to produce a tone the pickup is pushed toward a rotating wheel which has bumps on its surface. These are similar to the slots of the Alexanderson Alternator, and effectively modulate the field between the magnet and the coil to produce a tone.
Amplifying the Oscillation
So far we have purely relied on electromechanical techniques, however amplification is key to all modern oscillators, for which of course you require active devices. The simplest of these uses an inductor and capacitor to form a tank circuit. In a tank circuit energy sloshes back and forth between an inductor and capacitor. Without amplification, losses will cause the oscillation to quickly die out. However by introducing amplification (such as in the Colpitts oscillator) the process can be kept going indefinitely.
Oscillator stability is important in many applications such as radio transmission. Better oscillators allow transmissions to be packed more closely on the spectrum without fear that they might drift and overlap. So the quest for better, more stable oscillators continued. Thus the crystal oscillator was discovered, and productionized. This was a monumental effort.
Producing Crystal Oscillators
The video below shows a typical process used in the 1940s for the production of crystal oscillators:
Natural quartz crystals mined in Brazil were shipped to the US, and processed. I counted a total of 13 non-trivial machining/etching steps and 16 measurement steps (including rigorous quality control). Many of these quite advanced, such as the alignment of the crystal under an X-Ray using a technique similar to X-Ray crystalography.
These days our crystal oscillator production process is more advanced. Since the 1970s crystal oscillators have been fabricated in a photolithographic process. In order to further stabilize the crystal additional techniques such as temperature compensation (TCXO) or operating the crystal at a temperature controlled by the use of a heating element (OCXO) have been employed. For most applications this has proved accurate enough… Not accurate enough however for the timenuts.
Timenuts Use Atoms
For timenuts there is no “accurate enough”. These hackers strive to create the most accurate timing systems they can, which all of course rely on the most accurate oscillator they can devise.
Many timenuts rely on atomic clocks to make their measurements. Atomic clocks are an order of magnitude more precise than even the best temperature controlled crystal oscillators.
Bill Hammack has a great video describing the operation of a cesium beam oscillator. The fundamental process is shown in the image below. The crux is that cesium gas exists in two energy states, which can be separated under a magnetic field. The low energy atoms are exposed to a radiation source, the wavelength of which is determined by a crystal oscillator. Only a wavelength of exactly 9,192,631,770Hz will convert the low energy cesium atoms to the high energy form. The high energy atoms are directed toward a detector, the output of which is used to discipline the crystal oscillator, such that if the frequency of the oscillator drifts and the cesium atoms are no longer directed toward the detector its output is nudged toward the correct value. Thus a basic physical constant is used to calibrate the atomic clock.
While cesium standards are the most accurate oscillators known, Rubidium oscillators (another “atomic” clock) also provide an accurate and relatively cheap option for many timenuts. The price of these oscillators has been driven down due to volume production for the telecoms industry (they are key to GSM and other mobile radio systems) and they are now readily available on eBay.
With accurate time pieces in hand timenuts have performed a number of interesting experiments. To my mind the most interesting of these is measuring time differences due to relativistic effects. As is the case with one timenut who took his family and a car full of atomic clocks up Mt. Rainier for the weekend. When he returned he was able to measure a 20 nanosecond difference between the clocks he took on the trip and those he left at home. This time dilation effect was almost exactly as predicted by the theory of relativity. An impressive result and an amazing family outing!
It’s amazing to think that when Einstein proposed the theory of special relatively in 1905, even primitive crystal oscillators would not have been available. Spark gap, and Alexanderson alternators would still have been in everyday use. I doubt he could imagine that one day the fruits of his theory would be confirmed by one man, on a road trip with his kids as a weekend hobby project. Hackers of the world, rejoice.