Thursday, December 29, 2011

Electromechanical Solenoids

Electromechanical solenoids consist of an electromagnetically inductive coil, wound around a movable steel or iron slug (termed the armature). The coil is shaped such that the armature can be moved in and out of the center, altering the coil's inductance and thereby becoming an electromagnet. The armature is used to provide a mechanical force to some mechanism (such as controlling a pneumatic valve). Although typically weak over anything but very short distances, solenoids may be controlled directly by a controller circuit, and thus have very low reaction times.
The force applied to the armature is proportional to the change in inductance of the coil with respect to the change in position of the armature, and the current flowing through the coil (see Faraday's law of induction). The force applied to the armature will always move the armature in a direction that increases the coil's inductance.
Electromechanical solenoids are commonly seen in electronic paintball markers, pinball machines, dot matrix printers and fuel injectors.

Check out our full line of Solenoids in our online catalog.

Magnetic field of an infinite solenoid


In short: the magnetic field inside an infinitely long solenoid is homogeneous and its strength does not depend on the distance from the axis, nor on the solenoid cross-sectional area.
This is a derivation of the magnetic flux density around a solenoid that is long enough so that fringe effects can be ignored. In the diagram to the right, we immediately know that the flux density vector points in the positive z direction inside the solenoid, and in the negative z direction outside the solenoid. We see this by applying the right hand grip rule for the field around a wire. If we wrap our right hand around a wire with the thumb pointing in the direction of the current, the curl of the fingers shows how the field behaves. Since we are dealing with a long solenoid, all of the components of the magnetic field not pointing upwards cancel out by symmetry. Outside, a similar cancellation occurs, and the field is only pointing downwards.
Now consider the imaginary loop c that is located inside the solenoid. By Ampère's law, we know that the line integral of B (the magnetic flux density vector) around this loop is zero, since it encloses no electrical currents (it can be also assumed that the circuital electric field passing through the loop is constant under such conditions: a constant or constantly changing current through the solenoid). We have shown above that the field is pointing upwards inside the solenoid, so the horizontal portions of loop c doesn't contribute anything to the integral. Thus the integral of the up side 1 is equal to the integral of the down side 2. Since we can arbitrarily change the dimensions of the loop and get the same result, the only physical explanation is that the integrands are actually equal, that is, the magnetic field inside the solenoid is radially uniform. Note, though, that nothing prohibits it from varying longitudinally, which in fact it does.


A similar argument can be applied to the loop a to conclude that the field outside the solenoid is radially uniform or constant. This last result, which holds strictly true only near the centre of the solenoid where the field lines are parallel to its length, is important in as much as it shows that the flux density outside is practically zero since the radii of the field outside the solenoid will tend to infinity.
An intuitive argument can also be used to show that the flux density outside the solenoid is actually zero. Magnetic field lines only exist as loops, they cannot diverge from or converge to a point like electric field lines can (see Gauss's law for magnetism). The magnetic field lines follow the longitudinal path of the solenoid inside, so they must go in the opposite direction outside of the solenoid so that the lines can form a loop. However, the volume outside the solenoid is much greater than the volume inside, so the density of magnetic field lines outside is greatly reduced. Now recall that the field outside is constant. In order for the total number of field lines to be conserved, the field outside must go to zero as the solenoid gets longer.

What is a Solenoid?

A solenoid is a coil wound into a tightly packed helix. In physics, the term solenoid refers to a long, thin loop of wire, often wrapped around a metallic core, which produces a magnetic field when an electric current is passed through it. Solenoids are important because they can create controlled magnetic fields and can be used as electromagnets. The term solenoid refers specifically to a magnet designed to produce a uniform magnetic field in a volume of space (where some experiment might be carried out).

In engineering, the term solenoid may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid.

About Magnetic Sensor Systems

Background and Experience
Magnetic Sensor Systems (MSS) designs and manufactures high quality solenoids, electromagnets, driving electronics and other types of electro-mechanical components for a variety of industries and applications.
Established in 1983, Magnetic Sensor Systems is headquartered in Van Nuys, California, USA. The proximity of Magnetic Sensor Systems to both the major airport and seaport facilities of Southern California makes service to international customers very expedient without any freight forwarding or time consuming difficulties.
Through wise and aggressive use of its resources and technology, MSS has become one of the world's leading solenoid manufacturers with a global customer base.

Global Delivery
We serve global customers on a worldwide base. A truly global Company, we are committed to maintaining and developing our international sales and supporting a diverse client base.
This comes through our wish to ensure all orders are dispatched and delivered across the world with the shortest delivery time, in most cases within 1 to 5 days.
To make all of this possible required pre-negotiated and deeply discounted rates from major carriers such as DHL, FedEx and UPS.

Immediate Shipping
All products are available for immediate shipment. That is all solenoids and electromagnets presented in our catalog for all listed voltages, duty cycles and wire gauges, with all listed supporting electronics and hardware.
This shorter delivery cycle will enable Magnetic Sensor Systems' customers to shorten production cycles and implement just-in-time manufacturing.

Quality Policy
The management and employees of Magnetic Sensor Systems are committed to meeting or exceeding our customers' quality expectations and industry standards throughout the design, manufacturing, service and technical support phases. We will continuously improve our methods and the quality of our products and services through innovation, research and development, ongoing review, training, maintenance of a safe workplace, and the treatment of all with respect and dignity.

Off-the-shelf or Custom 
Magnetic Sensor Systems has an extensive family of standard products in variety of sizes and shapes ready to be shipped immediately from stock.
Where standard products are not quite right for your application, a competent staff of highly trained design engineers is always available to develop custom solenoid actuators, electromagnets and related products to be manufactured to any size or configuration. They also work with the customers' design staff to complete or augment any design already in process.
We also build complete value-added sub-assemblies with many levels of complexity.

In-house Manufacturing
Part of Magnetic Sensor Systems' competitive advantage is its state-of-the-art in-house manufacturing facility in North America combined with offshore manufacturing capabilities. Highly controlled processes, committed staff and extensive testing complement our product design strengths. This enables Magnetic Sensor Systems to supply the most demanding of clients from specialized small orders to high volume just-in-time deliveries. Magnetic Sensor Systems is ISO 9001:2000 certified.

Sales and Distribution
Magnetic Sensor Systems generally sells direct or through distribution partners, depending on the product in question. Please contact us to establish how best we can supply your needs.