Analog Clock

Richard of Wallingford pointing to a clock, his gift to St Albans Abbey.

16th-century clock machine Convent of Christ, Tomar, Portugal
Besides the Chinese astronomical clock of Su Song in 1088 mentioned above, in Europe there were the clocks constructed by Richard of Wallingford in St Albans by 1336, and by Giovanni de Dondi in Padua from 1348 to 1364. They no longer exist, but detailed descriptions of their design and construction survive,[22][23] and modern reproductions have been made.[23] They illustrate how quickly the theory of the mechanical clock had been translated into practical constructions, and also that one of the many impulses to their development had been the desire of astronomers to investigate celestial phenomena.

Wallingford’s clock had a large astrolabe-type dial, showing the sun, the moon’s age, phase, and node, a star map, and possibly the planets. In addition, it had a wheel of fortune and an indicator of the state of the tide at London Bridge. Bells rang every hour, the number of strokes indicating the time.[22] Dondi’s clock was a seven-sided construction, 1 metre high, with dials showing the time of day, including minutes, the motions of all the known planets, an automatic calendar of fixed and movable feasts, and an eclipse prediction hand rotating once every 18 years.[23] It is not known how accurate or reliable these clocks would have been. They were probably adjusted manually every day to compensate for errors caused by wear and imprecise manufacture. Water clocks are sometimes still used today, and can be examined in places such as ancient castles and museums. The Salisbury Cathedral clock, built in 1386, is considered to be the world’s oldest surviving mechanical clock that strikes the hours.[24]

Spring-driven
Main article: Torsion pendulum clock

Renaissance Turret Clock, German, circa 1570

Spring driven Matthew Norman carriage clock with winding key
Clockmakers developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability. Clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock’s accuracy, so many different mechanisms were tried.

Spring-driven clocks appeared during the 15th century,[25][26][27] although they are often erroneously credited to Nuremberg watchmaker Peter Henlein (or Henle, or Hele) around 1511.[28][29][30] The earliest existing spring driven clock is the chamber clock given to Phillip the Good, Duke of Burgundy, around 1430, now in the Germanisches Nationalmuseum.[4] Spring power presented clockmakers with a new problem: how to keep the clock movement running at a constant rate as the spring ran down. This resulted in the invention of the stackfreed and the fusee in the 15th century, and many other innovations, down to the invention of the modern going barrel in 1760.

Early clock dials did not indicate minutes and seconds. A clock with a dial indicating minutes was illustrated in a 1475 manuscript by Paulus Almanus,[31] and some 15th-century clocks in Germany indicated minutes and seconds.[32] An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.[33]:417–418[34]

During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworking towns of Nuremberg and Augsburg, and in Blois, France. Some of the more basic table clocks have only one time-keeping hand, with the dial between the hour markers being divided into four equal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. The cross-beat escapement was invented in 1584 by Jost Bürgi, who also developed the remontoire. Bürgi’s clocks were a great improvement in accuracy as they were correct to within a minute a day.[35][36] These clocks helped the 16th-century astronomer Tycho Brahe to observe astronomical events with much greater precision than before.[citation needed][how?]

Pendulum

The Dutch polymath and horologist Christiaan Huygens, the inventor of first precision timekeeping devices (pendulum clock and spiral-hairspring watch).[37]

From its invention in 1656 by Christiaan Huygens until the 1930s, the pendulum clock was the world’s most precise timekeeper, accounting for its widespread use.
The next development in accuracy occurred after 1656 with the invention of the pendulum clock. Galileo had the idea to use a swinging bob to regulate the motion of a time-telling device earlier in the 17th century. Christiaan Huygens, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (about 99.4 cm or 39.1 inches for the one second movement) and had the first pendulum-driven clock made. The first model clock was built in 1657 in the Hague, but it was in England that the idea was taken up.[38] The longcase clock (also known as the grandfather clock) was created to house the pendulum and works by the English clockmaker William Clement in 1670 or 1671. It was also at this time that clock cases began to be made of wood and clock faces to utilize enamel as well as hand-painted ceramics.

In 1670, William Clement created the anchor escapement,[39] an improvement over Huygens’ crown escapement. Clement also introduced the pendulum suspension spring in 1671. The concentric minute hand was added to the clock by Daniel Quare, a London clockmaker and others, and the second hand was first introduced.

Hairspring
In 1675, Huygens and Robert Hooke invented the spiral balance spring, or the hairspring, designed to control the oscillating speed of the balance wheel. This crucial advance finally made accurate pocket watches possible. The great English clockmaker, Thomas Tompion, was one of the first to use this mechanism successfully in his pocket watches, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern-day configuration.[40] The rack and snail striking mechanism for striking clocks, was introduced during the 17th century and had distinct advantages over the ‘countwheel’ (or ‘locking plate’) mechanism. During the 20th century there was a common misconception that Edward Barlow invented rack and snail striking. In fact, his invention was connected with a repeating mechanism employing the rack and snail.[41] The repeating clock, that chimes the number of hours (or even minutes) was invented by either Quare or Barlow in 1676. George Graham invented the deadbeat escapement for clocks in 1720.

Marine chronometer
A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day. This clock could not contain a pendulum, which would be virtually useless on a rocking ship. In 1714, the British government offered large financial rewards to the value of 20,000 pounds,[42] for anyone who could determine longitude accurately. John Harrison, who dedicated his life to improving the accuracy of his clocks, later received considerable sums under the Longitude Act.

In 1735, Harrison built his first chronometer, which he steadily improved on over the next thirty years before submitting it for examination. The clock had many innovations, including the use of bearings to reduce friction, weighted balances to compensate for the ship’s pitch and roll in the sea and the use of two different metals to reduce the problem of expansion from heat. The chronometer was tested in 1761 by Harrison’s son and by the end of 10 weeks the clock was in error by less than 5 seconds.[43]
https://en.wikipedia.org/wiki/Clock

Alarm Clocks

RCA Digital Alarm Clock with Large 1.4″ Display
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iHome iBT29BC Bluetooth Color Changing Dual…
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Electrohome EAAC601 Projection Alarm Clock with AM/FM Radio, Battery Backup, Auto Time Set, Dual Alarm, Nap/Sleep Timer, Indoor Temperature/Day/Date Display with Dimming, 3.5mm Audio Connection
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iHome iBTW39 Bluetooth Dual Alarm Clock with Wireless Charging, Speakerphone and USB Charging Port
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Sunrise Alarm Clock, Wake Up Light with 6 Nature Sounds, FM Radio, Color Light, Bedside Sunrise Simulator (New-White)
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BulbBotz ‘ Star Wars’ Plastic Wall Clock, Color:BB-8 (Model: 2020503)
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https://www.amazon.com/alarm-clocks/b?ie=UTF8&node=3734911

Alarm Clock Online

Google Assistant can double as an alarm clock. You simply ask it to set an alarm for you. The alarm then goes off as scheduled. It also supports countdown timers, reminders, and it can add things to your calendar. It always goes through the stock alarm clock app. That may or may not be a good thing. After all, you’re here looking for a new one, right? In any case, it’s good for those who use Google Assistant and need something super basic and free.
Price: Free / $2.99
I Can’t Wake Up does what the title suggests. It is for those who have trouble waking up in the morning. The app includes eight wake-up challenges to turn the alarm off. The idea being to make you coherent enough to get up before you hit the snooze button. It also has various alarm styles, some customization features, and some convenience features. It’s otherwise one of the more basic alarm clock apps. The free version and pro version are almost identical. The $2.99 pro version does remove ads.
The Rock Clock
Price: Free
The Rock Clock is definitely among the most unique alarm clock apps. It has some unusual features. They include 25 custom alarm tones created by The Rock. There is no snooze button because The Rock said so. The app can even wake you up the same time The Rock does. That dude is an early riser, so beware. This alarm clock app is for those who want to get motivated. It does a fairly decent job of doing so. It’s also free with no ads or in-app purchases.
Price: Free / Up to $3.99
Sleep as Android is among the most popular sleep tracking apps. The app studies you while you sleep. It then tries to analyze how well you’re sleeping. It does require you to sleep with your phone in the bed. The app also integrates with Google Fit, Samsung S Health, Galaxy Gear, Android Wear, Pebble (RIP), and Spotify. The app can even guess if you have sleep apnea. However, we don’t recommend that you use this as a diagnostic tool. Always consult a doctor! The app is free to download with a single $3.99 payment for the pro version.

10 best alarm clock apps for Android

Alarm Clock App

We as humans only have many things in common. We all eat, sleep, use the restroom and, usually, we all wake up after going to sleep. The alarm clock is a ubiquitous fixture in the bedroom and smartphones serve that purpose for a ton of people. Sometimes, the stock alarm clock app just doesn’t cut and you need something better, although we do recommend giving the stock alarm clock app on your device a good try first. Thus, we have put together a list of the best alarm clock apps for Android!
Price: Free / $1.99
Alarm Clock for Heavy Sleepers is a simple, but effect app. You can set an unlimited number of alarms. Additionally, the app does countdown alarms, recurring alarms, and one-time alarms. It even supports Android Wear, sleep stats, and more. Each one can have a challenge mode that tries to wake you up enough to not fall back asleep. That includes alarms for bed time so that you can get enough sleep. The free version and the paid version are virtually identical. The paid version does remove ads, though.
Alarm Clock for Heavy Sleepers
Price: Free / Up to $4.99
DOWNLOAD ON GOOGLE PLAY
Alarm Clock Xtreme is one of the most popular alarm clock apps. It has the standard alarm clock features. That includes music alarms, alarm challenges, auto-snooze, snooze button customization, and a lot more. The app also attempts to track your sleep. It doesn’t do as well as other apps do, but it can provide a little insight. The free version has some of the most annoying ads ever. We highly recommend picking up the paid version if you try this one.
Price: Free / $2.49
Alarmy calls itself the world’s most annoying alarm clock. This one has a unique premise. There is a registration spot that you set in your house. You take the phone to that spot when the alarm goes off. Otherwise, it doesn’t turn off. That may be too hardcore for some people. The app also includes various challenges and puzzles in order to get it to turn off. It’s one of the more creative alarm clock apps for sure.

Early Bird Alarm Clock
Price: Free / $1.99
Early Bird Alarm Clock is one of the basic alarm clock apps. It has the basic features like an almost infinite number of alarms. It also includes themes, alarm challenges, weather, and more. The alarm challenges are pretty decent as well. The app can also automatically change your alarm tone every day. That is definitely among its best features. It’s simple and it (usually) just works. The free version has advertising while the paid version does not. Otherwise both work the same way.
Early Bird Alarm Clock
Price: Free / $0.99
Good Morning Alarm Clock is one of the relatively newer clock apps. It also tries to track your sleep as well as wake you up. Of course, that means sleeping with your phone in your bed. Aside from that, it works well. Some of the more unusual features include a white noise generator, weather update features, a nightstand mode, and more. The sleep tracking is a bit rudimentary, but it may work for some people. The app’s only in-app purchase is $0.99 for the pro version.

24 Hour Clock

The 24-hour clock is the convention of time keeping in which the day runs from midnight to midnight and is divided into 24 hours, indicated by the hours passed since midnight, from 0 to 23. This system is the most commonly used time notation in the world today,[1] and is used by international standard ISO 8601.[2]

A limited number of countries, particularly English-speaking, use the 12-hour clock, or a mixture of the 24- and 12-hour time systems. In countries where the 12-hour clock is still dominant, some professions prefer to use the 24-hour clock. For example, in the practice of medicine the 24-hour clock is generally used in documentation of care as it prevents any ambiguity as to when events occurred in a patient’s medical history.[3] In the United States and a handful of other countries, it is popularly referred to as military time.[1][4]

Contents
1 Description
1.1 Midnight 00:00 and 24:00
1.2 Times after 24:00
1.3 Computer support
1.4 Military time
2 History
3 See also
4 References
5 External links
Description

A Russian 24 hour watch for polar expeditions from 1969, made by Soviet watchmaker Raketa. Polar nights or days make it necessary to use a 24-hour scale instead of 12.
A time of day is written in the 24-hour notation in the form hh:mm (for example 01:23) or hh:mm:ss (for example, 01:23:45), where hh (00 to 23) is the number of full hours that have passed since midnight, mm (00 to 59) is the number of full minutes that have passed since the last full hour, and ss (00 to 59) is the number of seconds since the last full minute. In the case of a leap second, the value of ss may extend to 60. A leading zero is added for numbers under 10, but it is optional for the hours. The leading zero is very commonly used in computer applications, and always used when a specifications require it (for example, ISO 8601).

Where subsecond resolution is required, the seconds can be a decimal fraction; that is, the fractional part follows a decimal dot or comma, as in 01:23:45.678. The most commonly used separator symbol between hours, minutes and seconds is the colon, which is also the symbol used in ISO 8601. In the past, some European countries used the dot on the line as a separator, but most national standards on time notation have since then been changed to the international standard colon. In some contexts (including the U.S. military and some computer protocols), no separator is used and times are written as, for example, “2359”.
Source By :
https://en.wikipedia.org/wiki/24-hour_clock