Definitive Guide to Relays and Solenoids

With the ever-growing number of electrical and electromechanical switches on the market, it can be confusing as to how each of them works and when they should be used. Two of the most confused devices are the relay and solenoid, which have similar operating principles but differ in their design and purpose. In this blog, we will discuss the similarities and differences between these two devices while also highlighting the applications in which each may be used.

The most common type of relay is electromagnetic, containing a soft iron core surrounded by a coiled wire. Also affixed to the device is an iron armature, which is connected to a movable yoke, and pair of conductive contacts. When electricity is applied to the coil, it creates a magnetic field that pushes the yoke, and therefore the armature, into a position where it physically touches the contacts. As such, the system acts as an electromechanical switch, which can be installed on a wide variety of devices. After the current is removed, the magnetic field is dissipated, which could trigger a moment of damaging overvoltage. To prevent this, electromagnetic relays also contain diodes and resistors placed along with the coil.

Relays are incredibly versatile and may be scaled to fit the needs of various applications. For example, a coaxial relay is implemented on radio antennas that can both transmit and receive signals. When the antenna is transmitting, it produces a large amount of power, which could potentially damage the receiving side. Relays are therefore used to switch between the two functions, never allowing both to be engaged simultaneously. Relays also play a critical role in overcurrent protection, particularly for electric motors. This specialized design features a strip instead of an armature designed to melt at a certain temperature. If overheating occurs, the strip will melt and break the contact, turning the motor off.

Solenoids also feature an electromagnetic coil and an armature. However, unlike relays, the armature in a solenoid is designed to move linearly across a horizontal axis, where it applies mechanical force to control an associated component. As the armature changes position, its inductance will also change, affecting how the magnetic field will interact with it. Since the armature can only move short distances and apply a low amount of mechanical force, they are best utilized in applications requiring quick actuation with high-sensitivity targets, such as solenoid valves.

The most common use of solenoids is in electromechanical locking mechanisms since they require quick and accurate actuation. When a power supply is triggered by either a remote or key card, the solenoid will react by moving the lock in place. An example of medical use for solenoids is the valve system used in dialysis machines, in which the armature-controlled valve tightly regulates the flow of the patient's blood and medication throughout the system. Additionally, solenoids may be found in the gearbox and air conditioning of automobiles. In all of these cases, the solenoid and its associated casing have been scaled to fit the specific application.

Whether you need reliable electromechanical relay or solenoid components, Part Orbit has you covered with an expansive inventory, rapid lead times, and significant cost savings. Further, we operate with AS9120B, ISO 9001:2015, and FAA AC 00-56B accreditation, thanks to the numerous quality assurance measures we have in place. We are also the only independent distributors to uphold a strict NO CHINA Sourcing policy, helping ensure every order is fully traceable or ships directly from a trusted manufacturer. Get started on the procurement process today with the submission of an RFQ to learn why many customers continually choose Part Orbit as their strategic sourcing partner.