|
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 |
Absolute encoders are he easiest to connect and use, after
potentiometers. One good reason to use Absolute encoders is because they never need to be recalibrated
unless you change the physical relationship between the
encoders and the antenna. Therefore if the antenna
position is changed while the controller board is not
operating, the controller will still read correctly when
it is restarted. 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. Calibration is very easy, only requiring one point of setting.
Wiring is also fairly easy, only requiring one 6 pin connector to
connect both elevation and azimuth encoders. This table lists the 3
types of absolute encoders that we have tested with, and the features of
each.
Click on the name in the list above to open each manufacturer's web page. The items below give more information about each encoder type to help in the decision process. Click the titles below for information about hardware and ordering, and then follow links to the Calibration and Detailed Configuration information. |
||||||||||||||||||||
US-Digital Absolute Encoders are the easiest to connect and use. The wiring is simple and available pre-made cables are available from US-Digital. Their measurement precision can be adjusted for low or high precision. There is really not much difference, but slightly better than .1 degree precision can be had by setting them to high precision. The best advantage to the USD encoders is using the Inclinometer version for elevation. That greatly simplifies your mechanical installation of the antenna mount. Note: Do not try to use US Digital and BritterEncoder encoders together. They use the same data lines and will interfere with each other. |
||||||||||||||||||||
BriterEncoder Absolute Encoders are a lot less expensive than the USD variety, but they are more complicated to set up, as they require an external adapter to work with our controllers. 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 available in a high or low precision model, but their precision cannot be adjusted. You have to order the more expensive high precision model. Low precision should be good enough for bands up to 1296, or higher, depending on your antenna size. One would definitely need the high resolution version for a 16 foot dish on 10 GHz! |
||||||||||||||||||||
Megatron Absolute Encoders are also a lot less expensive, and more complicated to set up, as they require an external adapter to work with our controllers. Also they do not have an inclinometer version. These encoders are really inexpensive, running about $50 or so. There are two models that can be used, ETS25 and MAB25 (ETS25 is current production). 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 correct output signals or data format to be compatible with the W2DRZ 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 W2DRZ Controller. With these adaptor boards, calibration and usage is the same as with the USD devices. |
| 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 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 |