What is a solenoid?
A solenoid is a device which converts energy into linear motion. This energy may come from an electromagnetic field, a pneumatic (air-powered) chamber or a hydraulic (fluid-filled) cylinder. Solenoids are commonly found in electric bell assemblies, automotive starter systems, industrial air hammers and many other devices which rely on a sudden burst of power to move a specific part. In order to understand the underlying principle of a solenoid, let’s examine a typical pinball machine. At the beginning of play, a steel ball rests on a rubber-tipped plunger. The plunger is held in place by a compression spring, which means it has no energy to move the ball when at rest. The player’s hand provides additional energy as the plunger assembly is pulled back. Upon release the compression spring forces almost all of the plunger pin’s kinetic energy on a small area of the steel ball. The ball is flung into the playing field and the pinball game begins. This manual plunger is a rudimentary exampl
A solenoid moves an iron core through the center of a wire coil when current flows through the coil. It is different to a relay which uses an electromagnet with a fixed iron core. Typical voltages used in solenoids are 12 and 24 volts. Some solenoids are controlled by pneumatic and hydraulic pressure instead of electricity.
A solenoid converts electrical power into linear mechanical power. Whereas a motor converts electrical power into a continuous rotational mechanical power, a solenoid has a finite, generally only short, mechanical movement. Solenoids are normally built by winding a coil of wire around a moveable soft iron core. When a current is passed through the coil, the core moves towards the centre of the solenoid. The current can be DC, AC, or a pulse-width modulated waveform that is partly DC and partly AC. This page should help you if you are using bought-in solenoids in your robot, or if you are trying to design your own solenoid or electromagnetic actuator.
In its simplest terms a solenoid is a device that converts electrical energy into mechanical movement. Two quite different designs are used to achieve linear or rotary actuation. Solenoids are usually integrated into a device that in turn, can clamp, position, switch, latch, lock, release, hold, divert etc. The movement of the solenoid is usually small with strokes 1-100mm, and angular rotations of under 95°. Simpler than an electric motor, and easier to control, solenoids can be very fast. For example a linear movement of 2mm or rotary travel of 45° can both be achieved in under 10ms. Well constructed solenoids are manufactured to exceed a 10 million cycle operating life.
