276XAXH-24D Datasheet, PDF (25/32 Pages) List of Unclassifed Manufacturers – Magnecraft PCB Reed Relays

Application Data
Magnecraft^® PCB & Reed Relays
Introduction
Printed circuit board (PCB) relays are compact relay devices used for power
management in control system designs which require the relay to be mounted
directly on the printed circuit board. They are used in applications where the relay
must be small enough to be mounted on a printed circuit board. They must be easy
to manufacture with the same machinery used in the printed circuit board line.
How Electromechanical PCB Relays Work
Electromechanical PCB relays consist of a coil, armature and contacts (see figure
below). When power is applied to the coil, the resulting magnetic field causes the
armature to move and the contacts to open or close.
Advantages
„„Higher contact ratings than reed relays and smaller than traditional plug-in relays
„„A wider range of form, fit and function than reed relays
„„UL recognized to meet industry standards for product safety and compliance
How Reed Relays Work
Reed relays consist of a coil wrapped around a sealed glass tube containing the
reeds and contacts (see figure below). When power is applied to the coil, the
resulting magnetic field causes the reeds to move and the contacts to close (1).
Advantages
„„Highly reliable due to longer mechanical and electrical life than
electromechanical relays
„„Can switch about ten times faster than an electromechanical relay with
similar ratings
„„Small, industry standard packaging which does not require unique machinery
to populate
Electromechanical PCB Relays vs. Reed Relays
Typical Electromechanical PCB Relay
Typical Reed Relay
COIL
REEDS
GLASS TUBE
COIL
ARMATURE
MECHANICAL
CONTACTS
CONTACTS
(1) Note that it is important to keep reed relays at a proper distance from each other because of
the possibility of magnetic-interaction between them. Proper magnetic shielding must be used
to contain stray magnetic fields. When installing reed relays into equipment, be aware of the
devices in the equipment which can produce magnetic fields. Position the relays as far away as
possible from any stray magnetic fields, and shield them to prevent false operations. A general
rule is to space reed relays no closer together than 0.5 inches.
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