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What Is The Difference Between Relay And Solenoid?

The difference between Relay and solenoid lies in their applications. A relay is an electrical component that can be used to electrically switch current from one circuit to another, while a solenoid is an electromagnet consisting of a coil of wire wound around an iron core.

To rephrase the difference for better understanding, an electrical relay initiates or stops the electrical current, whereas a solenoid regulates the current. A solenoid is basically an electromagnet, which can be turned on by grounding it. And a relay uses electromagnetic induction the way and purpose mentioned above.

In fine, they are identical in terms of functional ways or principles, but they differ widely in industrial applications. Let's examine the difference between these two electromechanical devices highly popular in the industrial sector.

A relay, an electrically operated switch, controls or isolates circuits. So, relays are ON/OFF devices used for building logical circuits. The main function of relays is to detect transmission or distribution faults and control high-powered circuits with a small signal. The most basic type of Relay has a magnetic core wrapped around a wire coil attached to a spring and one or more sets of contacts.

When an electrical current is applied to an electromechanical device, a magnetic field has produced that opens and closes the coil contacts. The coil's electrical properties depend on the electric current's voltage and frequency and its polarity.

When used to switch voltage, current, or power, this electromechanical device uses a small amount of energy. The devices are widely used in modern appliances, light fixtures, and cars. Relays are now being used in fuse boxes in modern cars.

Electrical Relay

What is Solenoid?

Solenoids are electrically powered devices that use an electromagnet to operate. There are several types of a solenoid, including magnetic and dielectric.

Solenoids offer various applications, including appliances and electronic hobbies. They are most commonly used in applications that require an automatic on/off feature. These devices are commonly used in automobiles and home appliances, but they are also found in pinball machines and electronic hobbyist projects. 

This is a small electrical device with a multi-turn coil of magnet wire and a frame. A solenoid's helix generates a controlled magnetic field and converts electrical energy into mechanical work.

Electrical Solenoid

Functions of Relay & Solenoid

Functions of Relay

Relays are important electrical devices and vital to understanding how they work and their use. The following are some ways relays can be used in your home and office.

  • A switch or a relay can be a simple way to interrupt a power source. They can also be used to control circuits. For example, you may use them to turn on lights when someone enters a room. Or you could have one that turns off all the lights when it's time to go to bed. A relay is an ideal solution if you want to make sure only certain people enter a room at night.
  • Relays have a moving part called an armature. Its movement opens and closes the contacts. The armature consists of a ferromagnetic metal, which is attracted to an electromagnet. The spring inside the armature allows the rotor to return to its original position.
  • The relay coil connects a source of electricity and will generate a magnetic flux proportional to the current flowing through it. The magnetic field causes the contact to move, and a normally-open contact will remain in that position.

Functions of Solenoid

  • The coil, in a solenoid, acts as a magnet when an electric current passes through it. It can produce a uniform magnetic field in a volume of space. It can also be used for mechanical work. Solenoids are used in doorbells and car door openers, as well as in air conditioning units.
  • Solenoid valves are electronically operated, eliminating the need for manual operation of valves. Solenoid valves operate by converting electrical energy into mechanical force. The electromagnetic field emitted by the coil causes the armature to move, opening or closing a switch or valve.
  • As the electric current flows through the wire, it generates a magnetic field. As the current passes through the wire, charged particles inside the magnetic field move around it in circles. When this process is repeated, coiling a wire produces a stronger magnetic field. The magnetic field is then concentrated within the coils, creating a solenoid.

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Difference Between A Solenoid and A Relay

A solenoid and a relay are electromechanical devices used to control the flow of electrical energy. While both devices have similar functions, they serve very different purposes. Read on to learn more about the differences between these two common types of electrical switches.

Functional Differences

  • A solenoid is a current-driven device. A true, current source is needed to supply the current needed by a solenoid. However, many applications use a voltage source to supply the required current. On the other hand, a relay is usually more appropriate for many types of applications.
  • Despite the similarities, the two electrical components are quite different. A solenoid turns electrical energy into a mechanical motion, and a relay controls the on-off path of other signals.
  • A relay requires more space than a solenoid, which is a less expensive alternative. However, if you need to switch large currents, a relay may be your best option.
  • The solenoid is an electromechanical switch operated by an electromagnetic field. A relay is a switching device but uses this same principle. The difference between a solenoid and a relay is in how they are controlled.
  • A solenoid has no moving parts; a relay contains mechanical contacts which open when current passes through them.
  • A relay is an electrical switch that opens and closes circuits. It controls a circuit by opening or closing contacts on a different circuit. The contacts are normally closed or open. Solenoids are actuators that convert electrical energy into mechanical motion. Solenoid valves are electrical switches that regulate fluid flow.
  • A solenoid is used in car starting systems, while a relay controls power lines and electrical loads.
  • Relays are designed to be positioned close to a current source. Solenoids are current-driven devices typically supplied with current using a true, current source.

Differing in Applications

On top of the differences above, industrial applications of Relay and solenoid are diverse. And what is the difference between the two in this regard? The answer lies in how they work.

A relay is an electrical component activated by an input source, such as a switch or sensor. It can actuate one or more separate outputs, making it versatile for many applications. From its initial conception to the more modern versions, the Relay has been used for everything from controlling lights to helping computers. The common application to discuss is an electric switch or circuit breaker. A typical example would be turning on your light when you enter your home in the evening.

On the other hand, Solenoids operate based upon magnetic flux changes that occur when current passes through them. They have less versatility than relays because their output depends solely on the amount of power passing through them. This makes them useful only for specific purposes like opening doors or activating lights.

But a solenoid is an electromagnet and can produce motion without moving parts. This makes them useful for controlling valves, pumps, fans, etc., which would otherwise require mechanical components to do so. Relays have been used since the early 20th century; however, their use has increased dramatically due to advances in technology.

Can Solenoid and Relay Replace/Swap with one another?

It's important to know the differences and similarities between a solenoid and a relay to replace one with the other safely. The difference between a solenoid vs. Relay is well covered by now. Now, let's see if the two electromechanical devices have some similarities to swap each other.

As for swapping one with the other, a solenoid can work as a relay as their functional policy is the same, but this would require rewiring and the use of an external power supply. A relay on its own cannot be used as a solenoid because it has no coil (solenoids are coils). So, you need another device that will act as a coil, or else your solenoid won't function properly.

Another shared feature is that both of these devices are used to facilitate electrical circuits and are common in many household appliances such as stoves or microwaves. Despite that, a relay and a solenoid are not the same things.


Do you need a relay for a solenoid?

If you need to operate a solenoid with an AC or DC power source, you should use a relay. A solenoid is an electromechanical device usually consists of a coil of wire wrapped around an iron core. This coil can be energized by either an AC or DC power source, and it will pull or push something, depending on the configuration.

Is starter solenoid a relay?

A starter solenoid is not a relay that is pretty clear from the debate starter relay vs solenoid. A starter solenoid has the same function as starting the engine of an automobile; however, unlike a relay, it does not require electrical power to function. A starter solenoid uses mechanical energy by engaging an internal mechanism that moves the ignition sidearm to fire the spark plug to start the engine.

What's the difference between a starter relay and a starter solenoid?

Knowing “what is a starter relay?” and “what does a starter relay do?” would help understand the difference even better. However, the two differ in that a starter relay has a vacuum hose to bring power from the manifold to its internal plunger while a starter solenoid doesn't. This means that you can use either type on any car with a manual transmission, but only one will work for cars with automatic transmissions.

Can the solenoid drain the battery?

A solenoid is a metal object activated by the key and used to start the car. The solenoid is often one of the main culprits for draining batteries. If you notice that your battery has been running low after starting the car, it may be because of the solenoid. It's easy to replace and should be replaced as soon as possible if suspected.

What happens if the starter relay goes bad?

A starter relay is a component of an engine that starts an engine bypassing power from the battery to the solenoid and coils, which send a high voltage charge to the ignition system. If this component goes bad, it can lead to issues such as not starting or not running properly. This part will need a replacement for the vehicle to start up again.

Wrap Up

Relay and solenoid are two types of electric switches used in electronics. They work differently, but the difference is not significant compared to their functions. Relays offer more than one input contact for each signal to provide a higher current capacity than solenoids. They also offer electrical isolation, allowing for safe operation with AC voltage sources.

It appears as if the difference between solenoid and Relay is that a relay activates with an electric signal, whereas an electromagnet activates a solenoid. However, this distinction can be misleading because both devices use magnetic force to activate them. The only real difference is how they're triggered: A relay requires electricity to operate while a solenoid does not require any power source.

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