Research Concepts RC2500 - Manual (Page 21)

14 RC2500 Antenna Controller Chapter 3 Installation/Setup
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas • 66218-9680 • USA www.researchconcepts.com
The antenna interface connections are made through DB-25 connectors. The low impedance nature of
these connections make them relatively immune to outside interference. To further increase the
interface’s immunity and to reduce possible emissions, a 25 conductor cable with an overall shield should
be used. A cable such as Belden 9948 or equivalent (RCI p/n CBL-25_22) is recommended.
The RC2500 communicates with the A.I.U. through the use of open-collector relay drivers. These low-
side drivers are designed to operate with 24VDC relays that have one side tied to the +24V loop supply
originating in the outdoor box. These relays should always have locally mounted back EMF or “buck”
diodes across the coil. Figure 3.3 illustrates typical interconnects for the Azimuth CW move command
line. The relay drivers of the RC2500 are optically isolated, have internal current limits and are protected
from over-voltage by metal oxide varistors.
In the version of the RC2500 that operates with the Harris 9135 A.I.U., 2 100mA high-side drivers are
used to transmit a PWM waveform that controls the speed of the azimuth and elevation motors.
The A.I.U. transmits status information back to the RC2500 through low impedance current loops. These
current loops drive the LED portion of opto-isolators in the RC2500. 5 to 10mA is the normal loop current
for these circuits. They will, however reliably operate at 1 mA. An open-circuit will indicate a limit has
been reached for most cases. This, combined with the opto-isolated drivers described above, allows the
A.I.U. and RC2500 to have 5000V of isolation.
Figure 3.3 Typical Antenna Interface Unit Limit Switch/ Relay-Drive Wiring
Open on Limit
Az CW Limit
+24VDC
to Drive Module or Contactor
Opens when jogging the AIU locally
Local/Remote Lockout
CCW Motion Lockout
Opens when antenna is moving CCW
Azimuth CW Contact Closure
RC2500 Drive Section
optically isolated
EStop
A.I.U.
RC2500
Drive
Drive Common
Limit
Limit Return