Solenoids are electromechanical devices used in a wide range of applications from controlling valves to converting electrical energy into linear mechanical motion. Though they may seem mysterious, solenoids actually operate through some basic scientific principles that are easy to understand. In this 3000 word beginner’s guide, we’ll explore what solenoids are, how they work, their key components, and common uses – with a focus on 36V solenoids.

What is a Solenoid?

A solenoid is a coil of wire that acts as an electromagnet when electricity passes through it. The key components are the coil, the plunger, and the housing. When energized, the coil creates a magnetic field that causes the plunger inside to move linearly. This linear motion can be used to mechanically control valves, switches, and other devices. Solenoids are found in a wide range of industrial, commercial and consumer products.

How Do Solenoids Work?

A solenoid works through the magic of electromagnetism. The coil of wire wraps around a movable ferromagnetic plunger. When electricity flows through the coil, it generates a magnetic field aligned with the axis of the coil. This magnetic field magnetizes the plunger, causing it to be attracted toward the center of the coil. However, the plunger is spring-loaded so it doesn’t fully enter the coil. The further in the plunger moves, the stronger the magnetic attraction. When electricity is removed, the magnetic field collapses, allowing the spring to push the plunger back out.

This linear push-pull motion of the plunger can be used to mechanically control valves, switches, latches and other devices. For example, a solenoid valve utilizes the plunger to open or close a valve by blocking or allowing fluid flow. Many modern engines use solenoid valves to control fuel injection and intake valves.

Key Components of a Solenoid


The coil is the component that creates the magnetic field when electricity passes through. It consists of insulated copper wire wrapped tightly around the solenoid tube many times. More windings result in a stronger magnetic field but also increase electrical resistance and power consumption. The gauge of the wire also impacts resistance and power.


The plunger, also called the armature, is the movable part that is magnetized and pulled into the coil when energized. It is typically made of soft ferromagnetic material like iron. The plunger may have a rod attached to mechanically transfer the linear motion. Springs are used to return it to the de-energized position.


The housing, frame or tube encloses the coil and provides a mounting point. It is made from steel or other ferromagnetic material to contain and direct the magnetic field. The housing also includes bushings to guide the plunger motion.

Solenoids voltage

Voltage is one of the key factors impacting solenoid design and performance. Higher voltage generally allows a solenoid to activate faster and produce greater force. But it also causes more heat and higher power consumption. 36V is a common solenoid voltage used in many applications.

Compared to 12V solenoids, 36V variants can create stronger magnetic fields enabling higher forces from more compact packages. But they require thicker coil wire to handle the increased current load. Common uses for 36V solenoids include industrial valves, diesel and natural gas engines, and automotive transmissions.

Force and Stroke Length

Two key specs for any solenoid are the force it can generate and the stroke length it can achieve.

The force, also called push or pull capacity, depends on factors like voltage, coil size and plunger area. More force allows a solenoid to operate heavier loads. Force may be provided as a single rating or a push/pull rating.

Stroke length is the distance the plunger travels between de-energized and energized positions. More stroke length increases the range of motion for mechanical control. Stroke length is physically limited by the solenoid body size.

Response Time

The response time indicates how fast the solenoid can react to being energized or de-energized. A faster response time allows quicker opening and closing of valves in applications like fuel injection systems. Response time is related to the coil resistance and voltage. Higher voltages enable lower resistance coils which can magnetize and demagnetize quicker. Response times are often specified in milliseconds (ms).

Duty Cycle

Duty cycle defines the amount of time a solenoid can safely remain energized versus de-energized. Excessive duty cycle for a given design can overheat the coil. Duty cycle may be provided as a percentage or a ratio. For example, a 10% duty cycle means the solenoid should not be energized more than 10% of the time to avoid overheating. This allows proper cooling during the 90% off time.

Common Solenoid Uses

Valves – Solenoids are widely used to actuate control valves for fluids and gases in diverse applications from irrigation systems to automobile transmissions. They allow valves to be electrically controlled versus manual operation.

Relays – Relays use solenoids to switch electrical contacts and control high power circuits with a low power signal. Relays are found in a vast array of electrical and electronic devices.

Linear Actuators – By attaching a rod to the plunger, the linear motion of a solenoid can be used to provide push-pull force for actuating other mechanisms.

Vending Machines – Solenoids in vending machines control the release of products. Coin activation energizes the solenoid to open the product delivery.

Pinball Games – The plunger that initially shoots the ball onto the playfield is controlled by a solenoid. Solenoids also control flippers and other playfield features.

Fuel Injectors – Modern fuel injected engines use solenoid valves to precisely control fuel delivery. The Engine Control Unit actuates the solenoids to open and close the valves.

Pneumatic Valves – Solenoids are used to control valves in pneumatic systems by regulating the flow of compressed air. This allows air cylinders and other pneumatic devices to be actuated.


In summary, solenoids provide an easy way to convert electricity into linear mechanical motion for controlling valves, switches, and other mechanical devices. Their versatility allows them to be utilized in diverse applications across industrial, commercial, and consumer sectors. Understanding the basic operating principles and key components makes their mysterious workings less daunting. Focusing on common specs like voltage, force, and response time enables selection of the optimal solenoid for a given application need. With this introductory guide, you should now have a solid grasp of how solenoids like the popular 36V variants function.