AdminRelay races are fun for all ages and can be played indoors or out. Be sure to have plenty of water for participants if playing outside.
Relays consist of a heavy-duty frame, control coil and iron core with contacts that close (close) or open (open). These contacts are controlled by a magnetic field.
The Coil
A copper coil wrapped around an iron core acts as an electromagnet. When DC current flows through the coil it creates a magnetic field that moves a spring loaded part called the armature. The armature then opens or closes the contacts depending on the polarity of the control signal. An attached spring returns the armature to its original position when the coil is de-energized or at rest.
The coil is held in a heavy frame that also contains the armature, contacts and other parts of the relay. The contact pins are connected to the armature via a braided bonding strap.
To troubleshoot a relay, start by making sure there is a connection between the coil and your power source. Check this with the continuity function of your multimeter. You should see a beep or a digital reading indicating there is a good connection between these two points. If not, it is time to move on to the next step.
The Armature
The armature of a relay is the moving part that opens and closes the contacts. It is mounted on a frame that can pivot on its yoke, and it has an attached spring that returns the movable arm back to its original position.
The electrical current passes through the armature core and armature winding to produce an electromagnetic field. As the armature is revolving the current in the armature winding cuts the lines of magnetic flux in the commutator. This induces an EMF in the commutator that reverses the current of the armature coil.
Each commutator segment is fitted with brushes which collect the current from the armature and deliver it to the load. These brushes must not be short-circuited as this would cause a voltage to build up in the armature. To reduce the voltage required to reverse the current in the armature, the commutator is built with a series of slots that are somewhat out of line up; this decreases arcing and makes the commutator more competent.
The Contacts
As the relay coil is energized it generates an electromagnetic force that attracts the opposite poles of the armature and causes them to connect or disconnect the movable contacts. This movement creates a connection between a pair of complementary sets of terminals called the N/C and the N/O contacts or pin outs.
The N/C contact or pinout is the main central switching lead that inherently forms one end of the movable pole. The other end is terminated with a metal strip called the N/O contact that also forms an end of the central switching lead.
When the relay is de-energized the movable contacts disengage and are returned to their default position by a force (usually mechanically assisted by a spring) or by gravity. This can cause arcing damage to the contact tips if they are exposed to high inductive or capacitive load currents. This is why relays are designed to operate quickly. They are also built to withstand mechanical shock loads and vibrations.
The Switch
A relay uses electromagnetism to convert small electrical inputs into much larger electric currents. This is done by opening and closing the contacts inside the relay. Relays are useful because they allow a single input to control multiple circuits without the need for additional components.
There are many different types of relays, each with its own unique characteristics. For example, the reed relay is a small relay that switches industrial components such as solenoids and starter motors. It consists of two ferromagnetic metal blades hermetically sealed in a glass tube that is filled with inert gas, which increases its lifespan.
The other type of relay is the SSR or solid state relay. It is a more modern design that does not have mechanical contact parts and offers a faster switching speed than its counterparts. The SSR does, however, waste power in the form of heat and has a contact arcing problem. 중계