Table of Contents
Advertisement
RC2000 Antenna Controller Interface Box
Many large antennas use a sensor attached directly to each of the fundamental axis of the antenna. The
sensor used may be a synchro, potentiometer, or a quadrature pulse encoder. A pulse type sensor attached
to the fundamental axis of the antenna is not suitable for use with RC2000 antenna controllers. The reason
for this requires a bit of explanation.
When a rising or falling edge is detected on the antenna controller's sensor input, the antenna controller
must determine whether to increment or decrement the position count. Since single phase pulse sensors are
used, the antenna controller must determine which way the antenna was last commanded to move, and
decrement or increment the count accordingly. With a pulse sensor connected directly to the antenna's
fundamental axis, when the antenna vibrates back and forth due to wind, the pulse sensor produces a steady
stream of pulses. The antenna controller will increment or decrement the count depending on which way
the antenna was last commanded to move. In reality the antenna is just vibrating in the wind and not really
moving. The result of this is an error in the position count maintained by the antenna controller.
The antenna controllers are designed to work with 36 volt actuators. With these actuators the pulse sensor
is connected directly to the motor. The motor typically drives either a worm or screw type gear, which will
not transmit wind motion from the antenna back to the motor. Therefore, no false counts are recorded by
the antenna controller. By placing a Hall-effect sensor on the shaft of the antenna motors drive, a similar
decoupling of wind vibration is achieved. On certain models of the RC2000 it is possible to disable the
accumulation of position pulses when the antenna is not commanded to move (or is in a coast interval
immediately following the release of the motor drive lines).
2.3 Polarization Control
If the polarization is controlled with something other than a polarotor, then an interface for a polarization
motor is necessary. Many popular rotating feeds use a 24 VDC motor with a potentiometer as the position
feedback device. These feeds can be driven directly by the RC2000 with the RC2KPOL option (ordered
separately). The RC2KPOL drive provides greater than 200mA @ 24 Volts for these feeds. In the event
that a high voltage DC or AC motor is used to drive the polarization axis, a scheme similar to that
described above for controlling the azimuth and elevation motors can be used with the RC2KPOL option
3. Circuit Description
The interface boxes described in the this document use a common printed circuit board to generate the
contact closures (described in the previous section) required to control the azimuth, elevation, and (if
needed) polarization axis of the antenna. That printed circuit board is designated 2K90INT-2.
The RC2KINT interface box consists of the 2K90INT board in a NEMA 4 enclosure. The user is
responsible for using the contact closures generated by the circuit board to control the antenna.
The RC2K90INT-1 interface box uses a single KBPB motor drive module. The motor drive module
accepts AC line voltage and contact closures produced by the 2K90INT-2 circuit board and generates the
drive voltage used to power the motors. The motor drive voltage produced by the KBPB motor drive
module is routed back onto the circuit board where a latching relay directs the current to either the azimuth
or the elevation axis. Simultaneous azimuth and elevation movement is not possible with the
RC2K90INT-1 interface box.
The RC2K90INT-2 interface box employs a pair of KBPB motor drive modules. Line voltage is connected
to both motor drive modules and each motor is directly connected to a motor module - motor drive voltage
does not pass through the 2K90INT-2 circuit board. With the RC2K90INT-2, simultaneous azimuth and
elevation movement is permitted.
KBPB DC Motor Drive Module
The RC2K90INT-1 and RC2K90INT-2 interface boxes employ KBPB DC motor drive modules
manufactured by KB Electronics, Inc. The KBPB motor drive modules use SCRs to rectify the AC line
voltage and control the voltage DC delivered to the armature of the motor being controlled. The KBPB-
6
Advertisement
Table of Contents
