How Relays Work - Basic working principle electronics engineering electrician amp
Understanding Relays: Components and Functionality
Introduction to Relays
- Paul introduces the topic of relays, highlighting their main parts, types, and operational principles.
- The video is sponsored by Telecontrols, a leading manufacturer in the automation industry since 1963, known for reliable switching relays.
What is a Relay?
- A relay is defined as an electrically operated switch that traditionally uses an electromagnet for operation; newer versions utilize solid-state technology.
- Relays allow control of circuits with low power signals and provide electrical isolation between controlling and controlled circuits.
Circuit Configuration
- There are two main circuits in a relay: the primary side (control signal) and the secondary side (load).
- The primary circuit connects to low voltage DC supply while the secondary circuit powers devices like fans or lights.
Electromagnetic Coil Functionality
- The electromagnetic coil generates a magnetic field when current flows through it; this can be demonstrated using compasses around the wire.
- Wrapping wire into a coil strengthens the magnetic field, which can be controlled by adjusting current levels.
Armature Mechanism
- The armature pivots to connect or disconnect circuits based on whether the electromagnet is energized or de-energized.
- Two basic types of relays are introduced: normally open (NO), where no electricity flows until activated, and normally closed (NC), where electricity flows until interrupted.
Solid State Relays (SSRs)
- SSR operation differs from electromechanical relays as they have no moving parts; they use semiconductors for switching functions.
- An LED replaces the electromagnet in SSR designs, providing optical coupling to activate a photosensitive transistor instead of mechanical movement.
Semiconductor Properties
- Explanation of n-type and p-type semiconductors highlights how they interact within solid state devices to facilitate current flow when activated by light from an LED.
Understanding Relays and Their Applications
Introduction to Relays
- Relays can control secondary circuits using light beams, stopping current flow when the LED is turned off. This allows for remote operation of devices.
Types of Relays
- The video discusses various types of relays, inviting viewers to share their experiences and ideas regarding relay applications in projects.
Normally Open Relay
- A normally open relay keeps the load off until the primary circuit is completed. An example includes controlling a fan with a bimetallic strip that bends with temperature changes.
Normally Closed Relay
- In contrast, a normally closed relay keeps the load on until the primary circuit is activated. This can be used in pump systems to maintain water levels by turning off when limits are reached.
Latching Relays
- Latching relays maintain power to the secondary circuit even after deactivation of the primary circuit. For instance, an elevator call button uses this feature to keep its light on until reset.
Mechanism of Latching Relays
- When pressed, a call button completes a circuit powering an electromagnet that holds a piston in place, keeping the lamp lit even after releasing the button.
Relay Configurations
Single vs Double Pole Relays
- Single or double pole refers to how many contacts are switched when energized. A double pole relay can control multiple circuits simultaneously (e.g., fan and warning light).
Double Throw Relay
- A double throw relay alternates between two circuits; it powers one device while turning another off based on whether the primary circuit is open or closed.
DPDT Relay Functionality
- A double pole double throw (DPDT) relay controls two states across separate circuits, switching connections based on primary circuit status.
Back EMF Considerations
- Back EMF occurs when power is cut from an electromagnet; it releases stored energy quickly which can damage circuits if not managed properly.
Mitigating Back EMF Effects
- Diodes are used to suppress back EMF by allowing current flow in one direction only, providing safe dissipation paths for excess energy during power cuts.
Conclusion