5
Connection
+24 VDC Wiring Diagrams
Use 18 AWG wire to connect positive DC line to the ‘+24V’ (DC+) terminal and the DC ground
to the ‘0V‘ (-DC) terminal. See text below about FG (
Chassis Ground).
Terminal Plug
: (MMI-720, 730, 750 Models) To make a connection, strip about 3/8” of
insulation off the end of the wire, and turn the connector screw counterclockwise until the gap
is wide open. Insert the wire all the way in, and turn the screw clockwise until it’s tight.
+24V 0V FG
Terminal Block
: (MMI-850, 1500 Models) To make a connection, strip about 3/8” of
insulation off the end of the wire, turn the connector screw counterclockwise until the hold
down plate is open wide enough to insert the wire. Insert the stripped portion of the wire
under the plate and turn the screw clockwise until it’s tight.
2.2.2 Grounding Requirements
Chassis ground must be used. DC ground is not directly coupled to Earth ground internally. It
is preferable not to ground DC negative return to chassis ground. Poor site earths can introduce
noise into a system. If necessary, an earth connection should be made from the power supply
return point to the central star earth point.
Ground conductors should be as short and as large in diameter as possible. The conductors must
always be large enough to carry the maximum short circuit current of the path being considered.
Ground conductors should be connected to a tree from a central star earth ground point. This
ensures that no ground conductor carries current from any other branch.
2.2.3 CE Requirements
To make an HMI comply with EMC directives, and to reduce susceptibility to electrical interference, a separate
#14 AWG ground wire should be taken to the chassis ground terminal of the power connector. This ground
connection should be run directly to the central star earth connection point (as recommended in most Installation
Instructions).
Use a ferrite core on the power wiring to reduce radiated emissions from the
DC power lines. It is recommended to use a 140Ohm@100MHz ferrite core
with the DC power lines looped through the core once. Position the ferrite
core less than 1” away from the DC power connection points on the back of
the HMI.
140 Ohm @ 100MHz ferrite core
Summary of Contents for MMI-1500
Page 2: ...ii...
