Universal Relay Wiring Instructions - Crime Guard 328i3 Installation Manual

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Operation manual (20 pages)

Operation manual (82 pages)

Table Of Contents

Table of Contents

At Rest

(Coil Not Energized)

In the views above, note the five terminals, or "pins". A relay's opera-

tion is really very simple. To understand its operation, consider the relay as

having two sections - the coil, pins 85 and 86; and 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 are 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 useful con-

figurations 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. For convenience,

this booklet shows the relay's "footprint"

view in its diagrams.