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What Is a Plastic Solenoid?

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  • Written By: Paul Scott
  • Edited By: E. E. Hubbard
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  • Last Modified Date: 06 September 2016
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    Conjecture Corporation
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A plastic solenoid is device enclosed in a plastic casing that supplies remote switching, adjustment, or actuation movement for other devices packaged. For example, a washing machine's plastic solenoid valve is activated by the machine's cycle timer circuit to open and allow water to flow into the machine. The valve is usually located deep in the machine's innards in such a position that the person operating the machine would never be able to reach, so the solenoid does the work remotely. Solenoids achieve their work courtesy of an electromagnetic field generated when their coil's are energized. The plastic solenoid is generally exactly the same as other types in regards to functioning, differing only in its plastic housing that prevents corrosion of the solenoid and shock hazards.

The solenoid is a universal workhorse used in applications as diverse as the family vacuum cleaner and the space shuttle. They provide simple, linear working motion to adjust machine parts, switch-on devices, or to actuate appliance functions. They are not the only types of remote movement devices, although they are by far the simplest consisting of only two parts. The first is a static coil of copper wire wrapped around a hollow, insulating core. The second part is a moving, spring-loaded plunger placed so that its end is located adjacent to the coil's core opening.

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When an electric current is passed to the coil of a plastic solenoid, the concentric nature of the windings creates a strong magnetic field around the coil. This magnetic force attracts the solenoid plunger, causing it to move rapidly into the coil's hollow core. The device being activated is attached to the plunger by means of a linkage, so this movement supplies the required actuation. When the coil power is turned off, the plunger's return spring pulls it back out of the coil, resetting the plunger for the next duty cycle. The electric current used to actuate the solenoid may be initiated manually by an operator or be sent via an automated process such as the washing machine's timer circuit.

Many environments where these devices are used feature constant exposure to moisture with a commensurate risk of corrosion of the solenoid parts and electric shocks or short circuits. To prevent this, the plastic solenoid is encased in a sealed, plastic enclosure that protects the internal mechanism. It also saves weight where it is relevant and makes the solenoid cheaper and easier to manufacture.

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