Rotating Feed With Potentiometer Position Feedback - Dawn CONTROL-1500A Manual

CONTROL-1500A Single Axis Antenna Controller
CONTROL-2000 Connection
J1-9 labeled RTN
J1-9 labeled RTN
The Polarotor Pulse output waveform is has an on time that varies from 0.8 to 2.2 milliseconds.
Varying the output waveform on time over this range results in approximately 200 degrees of
mechanical movement of the polarotor output shaft. The waveform off time is between 15 and
20 msec. Note that the waveform is only present when a polarization skew operating is in
progress or immediately after an operation terminates.

3.3.3 Rotating Feed with Potentiometer Position Feedback

With the RC2KPOL option, the CONTROL-1500A can control a 24 volt DC rotating feed with
potentiometer feedback (400 ma max motor drive current). The RC2KPOL is frequently used
to control a Seavey Engineering model 124 ESA rotating feed. The RC2KPOL is a daughter
board that is mounted on standoffs above the controller's digital board. If the RC2KPOL is
installed a 5 position, removable, clamp style connector will protrude from a rectangular
opening in the controller's back panel above the AGC adjustment pots. The connector is
labeled J4. If the RC2KPOL daughterboard is not present the rectangular opening will be
covered with silver tape. Note that the RC2KPOL daughterboard can optionally be configured
at the factory for other output voltages. Contact Research Concepts for more information. If
the current rating of the RC2KPOL motor drive outputs is not sufficient for a given application,
please contact the factory for other options.
3.3.3.1 Verifying the Potentiometer Center Position
The most common problem experienced during installation of a rotating feed is damage to the
potentiometer due to the potentiometer reaching its mechanical limit before the feed reaches
its mechanical limit. This problem has occurred quite often with Seavey feeds. Before using a
Seavey ESA 124 rotating feed with the CONTROL-1500, it is recommended that the user verify
that the feed's range of mechanical movement is within the position sense potentiometer's range
of mechanical movement. If the mechanical limit of the pot is reached before the mechanical limit
of the feed is reached, the torque of the motor can destroy the pot. The original pot used with
the Seavey feed was a Spectrol model 533 (1K ohm, 3 turn). Later models employ a Contelec
PD2205-5K (5k ohm, 5 turn.) To see if the potentiometer is centered properly, the following
procedure may be performed on a workbench.
Verifying Pot Center Position
1. Verify the total resistance of the potentiometer. This may be done by either reading the
value written on the side of the pot, or by measuring between the two non-wiper terminals
of the pot. For the Spectrol and Contelec pots this will be terminals 1 and 3.
DAWNco • 3340 S. Lapeer Rd • Orion, MI 48359-1320 • Ph (248) 391-9200 • Fax (248) 391-9207 • sales@DAWNco.com
Signal Description
Polarotor module.
DC Power return
Cable Drain Wire
Chapter 3 Installation/Setup
Polarotor Wire Color
(typical)
Black
Must be open and isolated
from ground at the
polarotor.
18