The stop action magnet, usually abbreviated to SAM, is an electromagnetic device used for the control of pipe organs and virtual pipe organs, and forms part of the organ's combination action. On a classical organ the device may be referred to as a drawstop solenoid. The SAM can be considered an electrical relay, the difference being that the SAM also has a drawknob or a tab, which enables it to be operated manually as well as electrically.
A SAM will have an armature which is operated by an electrically induced magnetic field and dependent on whether the SAM is being used with a drawknob or a tilting tablet on a classically voiced organ or with a flat tab on a theatre organ, the armature will move in either a linear fashion or with semi-circular movement, in a small defined arc. A drawknob or tab is attached to the armature to facilitate hand operation.
Each SAM consists of two coils of wire, wound on bobbins, which surround a single central, magnetically conductive pole piece or two separate pole pieces (determined by the designer) and will have one or more switching contacts or reed switches that are switched on or off by the movement of the armature. The switching contact is used to control which rank or ranks of pipes will sound when keys on a keyboard are depressed, although the actual 'rank switching' is often handled by a more complex electromagnetic or electronic relay system.
In mechanical operation using a SAM with a drawknob attached, a player will either pull the drawknob towards themselves to select an 'on' state, or push the drawknob away to select an 'off' state. The movement of the drawknob affects the state of the switch or reed contact. Similarly, with a SAM that utilises a tilting tablet, the player will tilt the tablet up or down by hand to operate it. With a theatre organ the tab attached to each SAM is raised or lowered by the player to operate the switch contact/s.
Whilst hand registering the organ is often carried out, this can only be used to facilitate small changes in the overall tonal colour, due to physical restrictions. i.e. The operator cannot operate more than one or two devices simultaneously, especially when using only one hand for registration, whilst playing keys with the other hand! This is where the true versatility of the SAM comes into play. By applying a low voltage electric current (usually between 12 and 30 volts at up to 0.5 ampere) to one or the other of a SAM's electromagnets (coils) the armature can be made to follow the same movement and thus operate its switching contact/s as if it had been actuated by a human operator. The advantage of electrical operation being that many SAMs can be electrically connected together and switched by the use of a single button (piston) depressed by the human player using only one finger. It can therefore be seen that operating many SAMs in simultaneous combination will have a far greater instantaneous effect on the sound of the organ (which is essential for tonal variety) than is achievable by the use of single SAMs. Furthermore, combinations of registration changes can be stored in electronic or electromechanical memory which forms part of the organ's combination action, for instant recall at the touch of a button (piston) and translated into electrical impulses used to operate multiple SAMs.
One further use of SAMs in multiples is to achieve instant cancellation of organ registrations either in banks or for the entire organ. Most organs will have a General Cancel button for the purpose of entire cancellation, whilst at least one style of pipe organ manufactured by the John Compton company in the 20th century uses an ingenious system known as Second Touch Cancel, where each SAM has an extra contact fitted which is operated by depressing any single SAM's tab past its normal 'on' position, and which serves to switch all associated SAMs in its department to the 'off' position.
A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts is touching current can pass between them, while when the contacts are separated no current can flow.
In electricity generation, a generator is a device that converts motion-based power or fuel-based power into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, gas turbines, water turbines, internal combustion engines, wind turbines and even hand cranks. The first electromagnetic generator, the Faraday disk, was invented in 1831 by British scientist Michael Faraday. Generators provide nearly all the power for electrical grids.
The pipe organ is a musical instrument that produces sound by driving pressurised air through the organ pipes selected from a keyboard. Because each pipe produces a single pitch, the pipes are provided in sets called ranks, each of which has a common timbre, volume, and construction throughout the keyboard compass. Most organs have many ranks of pipes of differing pitch, timbre, and volume that the player can employ singly or in combination through the use of controls called stops.
A tattoo machine is a hand-held device generally used to create a tattoo, a permanent marking of the skin with indelible ink. Modern tattoo machines use electromagnetic coils to move an armature bar up and down. Connected to the armature bar is a barred needle grouping that opens the skin for the ink to flow into. All electromagnetic coil machines are powered by a wired regulated DC power supplies which send an electric current through the copper coils wrapped around opposing magnets and then moves the armature bar up and down. In addition to coil tattoo machines, there are also rotary tattoo machines, which are operated with regulated rotary motors and are powered by a wired external RC power supply or a wireless battery pack attached to the machine. There are many types of rotary machines, some that look similar to coil machines and some that look more like "pens". Coil machines are usually each tuned for a single function, such as for shading, or lining or packing ink. Rotary machines are multifunctional, taking any size or type of needle or cartridge needle. "The basic machine is pretty much unchanged today, in recent years variations of the theme have crept into the market, namely Manfred Kohrs' rotary machine of 1978 or Carson Hill’s pneumatic machine that uses compressed air rather than electricity, but the principle is essentially the same."
In electrical engineering, a stepping switch or stepping relay, also known as a uniselector, is an electromechanical device that switches an input signal path to one of several possible output paths, directed by a train of electrical pulses.
An electric bell is a mechanical or electronic bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound. Electromechanical bells have been widely used at railroad crossings, in telephones, fire and burglar alarms, as school bells, doorbells, and alarms in industrial areas, since the late 1800s, but they are now being widely replaced with electronic sounders. An electric bell consists of one or more electromagnets, made of a coil of insulated wire around an iron bar, which attract an iron strip armature with a clapper.
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which the field current flows.
A wire spring relay is a type of relay, that has springs made from drawn wires of nickel silver, rather than cut from flat sheet metal as in the flat-spring relay. This class of relays provided manufacturing and operating advantages over previous designs. Wire spring relays entered mass production in the early 1950s.
Electromagnetic clutches operate electrically but transmit torque mechanically. This is why they used to be referred to as electro-mechanical clutches. Over the years, EM became known as electromagnetic versus electro-mechanical, referring more about their actuation method versus physical operation. Since the clutches started becoming popular over 60 years ago, the variety of applications and clutch designs has increased dramatically, but the basic operation remains the same today.
A brushed DC electric motor is an internally commutated electric motor designed to be run from a direct current power source and utilizing an electric brush for contact.
A dynamo is an electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
The pipe organ is played from an area called the console or keydesk, which holds the manuals (keyboards), pedals, and stop controls. In electric-action organs, the console is often movable. This allows for greater flexibility in placement of the console for various activities. Some very large organs, such as the van den Heuvel organ at the Church of St. Eustache in Paris, have more than one console, enabling the organ to be played from several locations depending on the nature of the performance.
Electromagnetic brakes or EM brakes are used to slow or stop vehicles using electromagnetic force to apply mechanical resistance (friction). They were originally called electro-mechanical brakes but over the years the name changed to "electromagnetic brakes", referring to their actuation method which is generally unrelated to modern electro-mechanical brakes. Since becoming popular in the mid-20th century, especially in trains and trams, the variety of applications and brake designs has increased dramatically, but the basic operation remains the same.
In electrical engineering, electric machine is a general term for machines using electromagnetic forces, such as electric motors, electric generators, and others. They are electromechanical energy converters: an electric motor converts electricity to mechanical power while an electric generator converts mechanical power to electricity. The moving parts in a machine can be rotating or linear. While transformers are occasionally called "static electric machines", since they do not have moving parts, generally they are not considered "machines", but as electrical devices "closely related" to the electrical machines.
Registration is the technique of choosing and combining the stops of a pipe organ in order to produce a particular sound. Registration can also refer to a particular combination of stops, which may be recalled through combination action. The registration chosen for a particular piece will be determined by a number of factors, including the composer's indications, the time and place in which the piece was composed, the organ the piece is played upon, and the acoustic environment within which the organ resides.
An electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet and an armature plate.
A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, although it is usually considered distinct from most other alternators, which use field coils rather than permanent magnets.
In engineering, a solenoid is a device that converts electrical energy to mechanical energy, using an electromagnet formed from a coil of wire. The device creates a magnetic field from electric current, and uses the magnetic field to create linear motion.
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