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31-403: Mechanical timers use clockwork to measure time. Manual timers are typically set by turning a dial to the time interval desired, turning the dial stores energy in a mainspring to run the mechanism. They function similarly to a mechanical alarm clock , the energy in the mainspring causes a balance wheel to rotate back and forth. Each swing of the wheel releases the gear train to move forward by

62-637: A mainspring , thus involving some form of escapement ; in other cases, hand power may be utilized. The use of wheels, whether linked by friction or gear teeth, to redirect motion or gain speed or torque , is typical; many clockwork mechanisms have been constructed primarily to serve as visible or implicit tours de force of mechanical ingenuity in this area. Sometimes clocks and timing mechanisms are used to set off explosives, timers, alarms and many other devices. The most common examples are mechanical clocks and watches. Other uses, most but not all obsolete, include: Clock generator A clock generator

93-579: A Greek shipwreck. There are many other accounts of clockwork devices in Ancient Greece, even in its mythology , and the mechanism itself is sophisticated enough to indicate a significant history of lesser devices leading up to its creation. At some point, this level of sophistication in clockwork technology was lost or forgotten in Europe, and only returned when brought from the Islamic world after

124-483: A crown upon his head, and a dove would bring him a Torah scroll. It's also said that when King Solomon stepped upon the throne, a mechanism was set in motion. As soon as he stepped upon the first step, a golden ox and a golden lion each stretched out one foot to support him and help him rise to the next step. On each side, the animals helped the King up until he was comfortably seated upon his throne. In ancient China ,

155-457: A curious account of automation is found in the Lie Zi text, written in the 3rd century BC. Within it, there is a description of a much earlier encounter between King Mu of Zhou (1023-957 BC) and a mechanical engineer known as Yan Shi, an 'artificer'. The latter proudly presented the king with a life-size, human-shaped figure of his mechanical handiwork ( Wade-Giles spelling): The king stared at

186-413: A series of gears driven by a spring or weight. A clockwork mechanism is often powered by a clockwork motor consisting of a mainspring , a spiral torsion spring of metal ribbon. Energy is stored in the mainspring manually by winding it up , turning a key attached to a ratchet which twists the mainspring tighter. Then the force of the mainspring turns the clockwork gears, until the stored energy

217-480: A shaft at the desired rate, and turn the cam. The most common application of this timer now is in washers , driers and dishwashers . This type of timer often has a friction clutch between the gear train and the cam, so that the cam can be turned to reset the time. Electromechanical timers survive in these applications because mechanical switch contacts may still be less expensive than the semiconductor devices needed to control powerful lights, motors and heaters. In

248-468: A small fixed amount, causing the dial to move steadily backward until it reaches zero when a lever arm strikes a bell. The mechanical kitchen timer was invented in 1926. The simplest and oldest type of mechanical timer is the hourglass - which is also known as "the glass of the hour" - in which a fixed amount of sand drains through a narrow opening from one chamber to another to measure a time interval. Short-period bimetallic electromechanical timers use

279-537: A small wooden cross and rosary in his left hand, turning and nodding his head, rolling his eyes, and mouthing silent obsequies. From time to time, he brings the cross to his lips and kisses it. It is believed that the monk was manufactured by Juanelo Turriano , mechanician to the Holy Roman Emperor Charles V . Often power for the device is stored within it, via a winding device that applies mechanical stress to an energy-storage mechanism such as

310-402: A special computer language called ladder logic. In PLCs, timers are usually simulated by the software built into the controller. Each timer is just an entry in a table maintained by the software. Computer systems typically have at least one hardware timer. These are typically digital counters that either increment or decrement at a fixed frequency, which is often configurable, and which interrupt

341-603: A specific time and can be used for tracking working or training time, motivating children to do tasks, replacing an hourglass -form egg timer in board games such as Boggle , or for the traditional purpose of tracking time when cooking. Apps may be superior to hour glasses, or to mechanical timers. Hour glasses are not precise and clear, and they can jam. Mechanical timers lack the customization that applications support, such as sound volume adjustments for individual needs. Most applications will also offer selectable alarm sounds. Some timer applications can help children to understand

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372-422: A thermal mechanism, with a metal finger made of strips of two metals with different rates of thermal expansion sandwiched together, steel and bronze are common. An electric current flowing through this finger causes heating of the metals, one side expands less than the other, and an electrical contact on the end of the finger moves away from or towards an electrical switch contact. The most common use of this type

403-475: Is an electronic oscillator that produces a clock signal for use in synchronizing a circuit's operation. The signal can range from a simple symmetrical square wave to more complex arrangements. The basic parts that all clock generators share are a resonant circuit and an amplifier. The resonant circuit is usually a quartz piezo-electric oscillator , although simpler tank circuits and even RC circuits may be used. The amplifier circuit usually inverts

434-463: Is in the "flasher" units that flash turn signals in automobiles , and sometimes in Christmas lights . This is a non-electronic type of multivibrator . An electromechanical cam timer uses a small synchronous AC motor turning a cam against a comb of switch contacts. The AC motor is turned at an accurate rate by the alternating current, which power companies carefully regulate. Gears drive

465-450: Is now less expensive than many mechanical and electromechanical timers. Individual timers are implemented as a simple single-chip computer system, similar to a watch and usually utilizing the same, mass-produced technology. Nowadays, many timers are implemented in software. Modern controllers use a programmable logic controller (PLC) instead of a box full of electromechanical parts. The logic is usually designed as if it were relays, utilizing

496-481: Is used up. The adjectives wind-up and spring-powered refer to mainspring-powered clockwork devices, which include clocks and watches, kitchen timers , music boxes , and wind-up toys . The earliest known example of a clockwork mechanism is the Antikythera mechanism , a first-century BC geared analogue computer, somewhat astrolabe -like, for calculating astronomical positions and eclipses , recovered from

527-675: The Crusades , along with other knowledge leading to the Renaissance . Clockwork finally recovered the equivalent of pre-Roman technological levels in the 14th century. As in Greek mythology, there are ambitious automation claims in the legends of other cultures. For example, in Jewish legend , Solomon used his wisdom to design a throne with mechanical animals which hailed him as king when he ascended it; upon sitting down an eagle would place

558-485: The Han Fei Zi and other texts. By the 11th century, clockwork was used for both timepieces and to track astronomical events, in Europe. The clocks did not keep time very accurately by modern standards, but the astronomical devices were carefully used to predict the positions of planets and other movement. The same timeline seems to apply in Europe, where mechanical escapements were used in clocks by that time. Up to

589-492: The 15th century, clockwork was driven by water, weights, or other roundabout, relatively primitive means, but in 1430 a clock was presented to Philip the Good , Duke of Burgundy , that was driven by a spring. This became a standard technology along with weight-driven movements. In the mid-16th century, Christiaan Huygens took an idea from Galileo Galilei and developed it into the first modern pendulum mechanism. However, whereas

620-452: The clock generator. TSGs are clocks that are used throughout service-provider networks, frequently as the building integrated timing supply ( BITS ) for a central office. Digital switching systems and some transmission systems (e.g., SONET, RREX, LUBI ) depend on reliable, high-quality synchronization (or timing) to prevent impairments. To provide this, most service providers use interoffice synchronization distribution networks based on

651-451: The concept of time, help them to finish tasks in time, and help them to get motivated. These applications are especially used with children with disabilities like ADHD , Down syndrome , etc., but everybody else can also benefit from them. Clockwork Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement ) or other mechanisms that work similarly, using

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682-543: The effect of taking away the heart, and found that the mouth could no longer speak; he took away the liver and the eyes could no longer see; he took away the kidneys and the legs lost their power of locomotion. The king was delighted. Other notable examples include Archytas 's dove, mentioned by Aulus Gellius . Similar Chinese accounts of flying automata are written of the 5th century BC Mohist philosopher Mozi and his contemporary Lu Ban , who made artificial wooden birds ( ma yuan ) that could successfully fly, according to

713-410: The figure in astonishment. It walked with rapid strides, moving its head up and down, so that anyone would have taken it for a live human being. The artificer touched its chin, and it began singing, perfectly in tune. He touched its hand, and it began posturing, keeping perfect time...As the performance was drawing to an end, the robot winked its eye and made advances to the ladies in attendance, whereupon

744-592: The king became incensed and would have had Yen Shih [Yan Shi] executed on the spot had not the latter, in mortal fear, instantly taken the robot to pieces to let him see what it really was. And, indeed, it turned out to be only a construction of leather, wood, glue and lacquer, variously coloured white, black, red and blue. Examining it closely, the king found all the internal organs complete—liver, gall, heart, lungs, spleen, kidneys, stomach and intestines; and over these again, muscles, bones and limbs with their joints, skin, teeth and hair, all of them artificial...The king tried

775-532: The number used in the divider or multiplier to be changed, allowing any of a wide variety of output frequencies to be selected without modifying the hardware. The clock generator in a motherboard is often changed by computer enthusiasts to control the speed of a CPU , FSB , GPU or RAM . Typically the programmable clock generator is set by the BIOS at boot time to the selected value; although some systems have dynamic frequency scaling , which frequently re-programs

806-795: The past, these electromechanical timers were often combined with electrical relays to create electro-mechanical controllers. Electromechanical timers reached a high state of development in the 1950s and 1960s because of their extensive use in aerospace and weapons systems. Programmable electromechanical timers controlled launch sequence events in early rockets and ballistic missiles . As digital electronics has progressed and dropped in price, electronic timers have become more advantageous. Electronic timers are essentially quartz clocks with special electronics, which can achieve higher precision than mechanical timers. They have digital electronics, but may have an analog or digital display. Integrated circuits have made digital logic so inexpensive that an electronic timer

837-489: The processor when reaching zero. An alternative design uses a counter with a sufficiently large word size that it will not reach its overflow limit before the end of life of the system. More sophisticated timers may have comparison logic to compare the timer value against a specific value set by software, which triggers some action when the timer value matches the preset value. This might be used, for example, to measure events or generate pulse-width modulated waveforms to control

868-480: The signal from the oscillator and feeds a portion back into the oscillator to maintain oscillation. The generator may have additional sections to modify the basic signal. The 8088 for example, used a 2/3 duty cycle clock, which required the clock generator to incorporate logic to convert the 50/50 duty cycle which is typical of raw oscillators. Other such optional sections include frequency divider or clock multiplier sections. Programmable clock generators allow

899-491: The software. Due to the increasing popularity of mobile phones , many timer apps have been developed that mimic the old mechanical timer, but which have also highly sophisticated functions. These apps are also easier to use, because they are available at once, without any need to purchase or carry separate devices. Timers can be software applications phones, smartwatches , or tablets . Some of these apps are countdown timers , stopwatches , etc. These timer apps can be set for

930-421: The speed of motors (using a class D digital electronic amplifier). One specialist use of hardware timers in computer systems is as watchdog timers, which are designed to perform a hardware reset of the system if the software fails. These types of timers are not devices nor parts of devices, they exist only as software. They rely on the accuracy of a clock generator usually built into a hardware device that runs

961-461: The spring or the weight provided the motive power, the pendulum merely controlled the rate of release of that power via some escape mechanism (an escapement) at a regulated rate. The Smithsonian Institution has in its collection a clockwork monk, about 15 in (380 mm) high, possibly dating as early as 1560. The monk is driven by a key-wound spring and walks the path of a square, striking his chest with his right arm, while raising and lowering

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