Understanding the magic behind these little mystery boxes can really help in electrical troubleshooting(which everyone loves doing :whatever
as well as installing aftermarket components.
Pull back the curtain and you see................
A relay is an electromechanical switch........when both power and ground are applied to the ends of the coil, the relay activates which causes mechanical contact points to either complete or open a circuit. It gives you the ability to use a small amount of current to switch large amount of current.
In the views above, note the five terminals, or "pins". A relay's operation is really very simple. Consider the relay as having two sections:
1.The coil, pins 85 and 86
2.The contacts, pins 30, 87 and 87a.
When negative ground is supplied to one end of the coil, and positive voltage is supplied at the other end, the coil creates a magnetic field which activates the relay. This magnetic field attracts the armature, which is attached to pin 30 with a flexible joint, just like a hinge. Inactivated, or "at rest", the armature connects pin 30 to pin 87a. When the relay is activated, the armature connects pin 30 to pin 87. The terms used to describe the contact points thus: pin 30 switches between pins 87a and 87, so it is "Common" to both and is usually referred to as COM. In the relay's normal condition, at rest, pin 30 is connected to pin 87a, making pin 87a "Normally Closed" or NC. Pin 87 is not connected to pin 30 at rest, so its status is "Normally Open" or NO. This type of relay is defined as "Single Pole Double Throw" or SPDT. This term means that the single armature terminal (or pole, pin 30) can be connected (or "thrown") to two other terminals, pins 87a and 87.
The SPDT relay is one of the most common configurations due to its flexibility - it can be used as a switching device, to isolate circuits, to interrupt circuits and to interrupt and switch at the same time.
as well as installing aftermarket components.Pull back the curtain and you see................
A relay is an electromechanical switch........when both power and ground are applied to the ends of the coil, the relay activates which causes mechanical contact points to either complete or open a circuit. It gives you the ability to use a small amount of current to switch large amount of current.
In the views above, note the five terminals, or "pins". A relay's operation is really very simple. Consider the relay as having two sections:
1.The coil, pins 85 and 86
2.The contacts, pins 30, 87 and 87a.
When negative ground is supplied to one end of the coil, and positive voltage is supplied at the other end, the coil creates a magnetic field which activates the relay. This magnetic field attracts the armature, which is attached to pin 30 with a flexible joint, just like a hinge. Inactivated, or "at rest", the armature connects pin 30 to pin 87a. When the relay is activated, the armature connects pin 30 to pin 87. The terms used to describe the contact points thus: pin 30 switches between pins 87a and 87, so it is "Common" to both and is usually referred to as COM. In the relay's normal condition, at rest, pin 30 is connected to pin 87a, making pin 87a "Normally Closed" or NC. Pin 87 is not connected to pin 30 at rest, so its status is "Normally Open" or NO. This type of relay is defined as "Single Pole Double Throw" or SPDT. This term means that the single armature terminal (or pole, pin 30) can be connected (or "thrown") to two other terminals, pins 87a and 87.
The SPDT relay is one of the most common configurations due to its flexibility - it can be used as a switching device, to isolate circuits, to interrupt circuits and to interrupt and switch at the same time.
