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This page describes the various kinds of encoders that the CT-2 controller is designed to work with, and provides detail on the usage and other considerations for each.


Potentiometers are the easiest encoders to use because the CT-2 has on-board Analog to Digital converters.  By connecting your 'pots' directly to the CT-2, and calibrating, the antenna position can be read without any further hardware.  The potentiometers are connected via the DIN-8 jack on the board.  The connection information is shown here: Potentiometer Readouts

US-Digital Absolute Encoders are the easiest to connect and use, after potentiometers.  The wiring is simple and available pre-made from US-Digital.  Absolute encoders are normally 'geared' one to one with the rotation of your antenna, and provide an absolute position value.  In this respect they are like potentiometers, but much more accurate.  The following links will take you to the various locations in this web where information on hardware and software for use with Absolute encoders can be found.

Hardware and wiring  -  Calibration  -  Detailed Configuration

Megatron Absolute Encoders are also usable and although they are a lot less expensive than the USD variety, they are more complicated to set up.  Also they do not have an inclinometer version so one would have to build an inclinometer (like with using a pendulum) or gear it as with an azimuth encoder.  These encoders are really inexpensive, running about $50 or so.  There are two models that can be used, ETS25 and MAB25.  I don't see much difference when using them.  They can be purchased from P3 America, in San Diego, California.

These encoders do not have the proper output signals or data format to be compatible with the Drz Controller (which was designed for US Digital's can-bus format.)  However an adaptor board is available from Gary, N8CQ. Using this board the encoder will plug in or mount to the adaptor board and the board is compatible with the RJ11 connectors used with the Drz Controller.  With these adaptor boards, calibration and usage is the same as with the USD devices.  For more information use this link: Megatron Absolute Encoders

Hardware and wiring  -  Calibration  -  Detailed Configuration

The CT-2 controller can work with several makes of pulse type encoders that produce what is called a "quadrature" data output stream.  While designed for the US-Digital incremental encoders, there are several other manufacturers of incremental encoders whose products can be used. The usage of incremental encoders for the CT-2 has been a work in progress and several hardware and software changes have been made over the years as we gained experience with these versatile encoders.  One improvement has been the addition of the capability to use the 'index pulse' that is provided with some incremental encoder models.  This provides a means to reliably reset the pulse count to the exact value required by your antenna calibration, automatically in many cases, or manually when necessary. See Using the Index Pulse, below.

Incremental 360 Encoders
Starting with version 5.21, we have added the new encoder type called "Incremental 360".  This type was designed for the Slew Drives, but can be used with any incremental encoder that is geared 1:1.  An encoder that is geared 1:1 can be set up using the regular "Incremental" type, but it is easier to select the "Incremental 360" type.

Note that encoders that are geared 1:1 with the azimuth or elevation drive cannot be 'geared up' for more precision, nor can they use an index pulse.  To make calibration and position setting easier, when Incremental 360 is set, the encoder configuration screen will show a field where the actual pulse count per revolution can be set.  Once this is set, calibration is simply a matter of aiming the antenna to a known direction, and then using the 'Set Current' field and button in the calibrate window to set it.  See the calibration section for more details.


Incremental Encoders - Hardware and electrical connection details for incremental encoders
Calibration - Details on setting up and calibrating incremental encoders.|
Conversion Boards - How to handle pulse train drive levels and interference problems
Detailed Configuration - How to select and set up the encoders
CT-2 Modifications for use with Index Pulse