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RC2000 Antenna Controller Interface Box
The circuit associated with latching relay K4 is used by the RC2K90INT-1 interface box. With the
RC2K90INT-1 interface box a single KBPB DC motor drive module is present and the latching relay is
used to route the motor drive current to either the azimuth or elevation axis. The relay will not be included
with the RC2K90INT-2 and RC2KINT model interface boxes. When an azimuth control input signal is
applied to the AZ1_CTL and AZ2_CTL inputs the K4 relay coil labeled 'LATCH_AZ' on the schematic is
energized and the inputs labeled A1_KBPB and A2_KBPB (connected to the A1 and A2 outputs of the
KBPB) are connected to the azimuth motor via the AZMOT1 and AZMOT2 outputs. The diode bridge
formed by diodes D6, D7, D8, and D9 insures that an azimuth control signal of either polarity will result in
a unipolar voltage being applied to the 'LATCH_AZ' coil of the relay. When the azimuth control signal
generated by the RC2000 is removed the latching relay stays in the 'azimuth' position.
In a similar fashion, when an elevation control input signal is applied to the EL1_CTL and EL2_CTL
inputs the 'RESET_EL' coil of the K4 relay is energized and the relay contacts are configured to connect
the A1_KBPB and A2_KBPB contacts to the elevation motors via the ELMOT1 and ELMOT2 outputs.
The diode bridge formed by D12, D13, D14, and D15 allows an elevation drive current of either polarity to
activate the 'RESET_EL' coil of the relay. When the elevation control input is removed the relay will stay
in the 'elevation' position until an azimuth input is applied. It is necessary to use a latching relay to select
the azimuth or elevation axis to support the dynamic braking capability of the motor drive module. If a
non latching relay were used, when the control input is removed (for one of the two axis) the relay would
switch while the motor is braking (and current is flowing). This would defeat the braking action and
generate noise as the relay contacts open with a load applied.
The RC2000D antenna controller supports dual speed azimuth and elevation movement when used with the
interface box. With the RC2000D software the controller's polarotor control output may be used to
activate relay K1 on the 2K90INT-2 board. This relay provides a pair of speed control channels which can
be used with either the KBPB DC motor drive module (in the RC2K90INT-1 or RC2K90INT-2 interface
boxes) or a user supplied controller (with the RC2KINT interface box) to obtain dual speed azimuth and
elevation movement. When used with other members of the RC2000 controller family only single speed
azimuth and elevation movement is available.
The K1 relay is powered with 5.7 volts DC via the terminals labeled +5.7V and Return. 5.7 volts is
available at the back panel of the RC2000 antenna controller. To activate the relay (and select high speed
movement) 5 volts is applied to the terminal labeled Pulse. Resistor R1 is a dropping resistor on the base
of transistor Q1 to limit the voltage at the base to approximately 0.7 volts. When Q1 turns on the relay is
activated. The relay provides two speed control channels. Each channel consist of a pair of
potentiometers. Only a single channel will be considered. For the KBPB1 speed control channel, the
KBPB1_FST and KBPB1_SLO pots (designated P2 and P3, respectively) are connected to the P3_KBPB1
and P1_KBPB1 terminals. When fast speed is selected the voltage at the wiper of the KBPB1_FST
terminal is presented to the P2_KBPB1 terminal. When slow speed is selected the voltage on the wiper of
the KBPB1_SLO pot is connected to the P2_KBPB1 terminal. If contact closures are required rather than
switched potentiometer wipers the potentiometers can be replaced with jumpers.
Diodes D1, D4, D5, D10, D11, D18, D19, D22, and D23 are used to suppress the back emf induced in the
relay coils when the relays are de-energized. These are sometimes referred to as 'buck diodes'.
The connection of the 2K90INT-2 circuit board to the KBPB DC motor drive module(s) varies with the
type of interface box (RC2K90INT-1 or RC2K90INT-2) as well as the type of controller (the RC2000D
software supports dual speed azimuth and elevation movement, other models of the RC2000 controller
only support single speed azimuth and elevation movement). The wiring schematics for the various
configurations are given in figures 4, 5 and 6.
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