How Relays Work - Basic working principle electronics engineering electrician amp

Summary

In this informative video from EngineeringMindset.com, Paul explains the fundamentals of relays, their components, and operation. Relays are electrical switches that control circuits using low power signals and provide electrical isolation. The video covers electromechanical and solid-state relays, highlighting their differences and applications. It also explores various types of relays, such as normally open, normally closed, latching, and double pole double throw (DPDT), with practical examples of their use in everyday devices. Furthermore, it touches on the importance of managing back electromotive force (back EMF) to protect circuits.

Takeaways

• 🔌 Relays are electrically operated switches that can be controlled by low power signals and are used to control circuits and ensure electrical isolation.
• 📡 Telecontrols is a leading manufacturer in the automation industry, offering reliable switching relays and a free relay configuration cheat sheet.
• 🧲 Traditional relays use an electromagnet to operate a mechanical switch, while newer versions, like solid-state relays (SSRs), use electronics without moving parts.
• 🔘 Relays consist of a primary and secondary circuit; the primary provides the control signal, and the secondary contains the load to be switched and controlled.
• 💡 The primary side of a relay typically includes an electromagnetic coil that generates a magnetic field when current passes through it.
• 📍 The armature in a relay is a pivoted component that moves in response to the magnetic field generated by the electromagnet, connecting or disconnecting the secondary circuit.
• 🔄 There are two basic types of relays: normally open (load is off until the primary circuit is complete) and normally closed (load is on until the primary circuit interrupts).
• 🌟 Solid-state relays use an LED and a photosensitive transistor for optical coupling and switching, eliminating the need for a mechanical moving contactor.
• 🔄 Latching relays maintain their last position without the need for continuous input or current, useful for applications like elevator call buttons.
• 🔄 Relays can have single or double poles, and single or double throws, allowing for multiple circuits to be controlled from a single primary circuit.
• ⚡ Back EMF, or electromotive force, is a phenomenon in electromagnets that can produce voltage spikes; diodes can be used to suppress this and protect circuits.

Q & A

What is the primary function of a relay?

A relay is an electrically operated switch that is used to control a circuit using a low power signal or to control several circuits by one signal, ensuring complete electrical isolation between the controlling and controlled circuits.

Why are relays important in electrical circuits?

Relays are important because they can reduce the current that flows through the primary control switch, allowing a low amperage switch or sensor to control a much higher capacity load.

What are the two main circuits found in a relay?

The two main circuits in a relay are the primary side, which provides the control signal to operate the relay, and the secondary side, which contains the load that needs to be switched and controlled.

What is the role of the electromagnetic coil in a relay?

The electromagnetic coil in a relay generates a magnetic field when current passes through it, which is used to mechanically operate the switch by attracting or repelling the armature.

What is the difference between a normally open and a normally closed relay?

A normally open relay has no electricity flowing in the secondary circuit until the primary circuit is complete, turning the load on. A normally closed relay has the secondary circuit complete and the load on by default, and it breaks the circuit when the primary circuit is energized.

How do solid-state relays (SSRs) differ from electromechanical relays?

Solid-state relays operate without moving parts, using the electrical and optical properties of semiconductors for input and output isolation and switching functions, unlike electromechanical relays which use an electromagnet and mechanical movement.

What is the purpose of the LED in a solid-state relay?

In a solid-state relay, the LED provides optical coupling by shining a beam of light into a photosensitive transistor, controlling the operation of the relay by turning the LED on and off.

What is the significance of the term 'pole' when discussing relays?

The term 'pole' refers to the number of contacts switched when the relay is energized, allowing multiple secondary circuits to be energized from a single primary circuit.

What is a latching relay and how does it differ from a standard relay?

A latching relay is designed to remain in the last position it was in without the need for any further input or current after being activated, unlike a standard relay which returns to its original position once the primary circuit is de-energized.

What is the purpose of a double pole double throw (DPDT) relay?

A DPDT relay is used to control two states on two separate circuits, allowing for the switching between different combinations of on and off states for multiple loads.

Why is it necessary to suppress back EMF in relay circuits?

Back EMF, or electromotive force, can produce large voltage spikes when the electromagnetic field collapses after power is cut, which can damage the circuit. Suppressing back EMF, often with a diode, safely dissipates the energy and protects the circuit.