|J2, the RJ45 connector is for
incremental encoders that have differential outputs like
those available from US Digital. While it looks like it
should work with any of their differential output
encoders, we have only tested with the S2
and T2 series encoders.
The output of these encoders is TTL level differential data. While the CT-1 controller can receive this TTL data directly, due to noise pickup from relays, motors, etc, and strong RF fields, and for lightning protection, the data must be converted to some more robust format before being sent down the line to the controller board. There are two schemes currently developed to do this. One is RS232 level conversion and the other is RS485 level conversion. RS485 is the more robust of the two and is recommended for longer lines and severe noise or RF environments. Once the converted signal reaches the vicinity of the controller board, it must be converted back to a TTL level before being applied to the board via J2.
If you wish to build up your own level conversion, you may choose either the RS232 or the RS485 method. The schematics are presented below on this page.
|1||Differential input for Azimuth - B|
|2||Differential input for Azimuth - A|
|4||Differential input for Elevation - B|
|5||Differential input for Elevation - A|
|7||+12 vdc out|
|8||+12 vdc out|
|Following are schematics
and connection information for building your own RS232
level converters for incremental encoders. There are two
schematics shown, first a single one to be used at the
encoder end of the line, and second a dual converter to
be used at the controller end of the line. If only one of
your encoders is an incremental encoder then the dual
encoder design can be simplified to only use one set of
At the right hand side of the single converter schematic there are two RJ45 jacks labeled J1 and J2. These are the RS232 level connections that connect to the main line between the encoder location and the controller location. They are wired in parallel, so that one of them can be used as an input from the second board and encoder. Below is a block diagram showing the configuration.
|One of these converter boards is
required for each incremental encoder, so if you use
incremental for both elevation and azimuth, you will need
The single converter boards need to be jumpered for their intended purpose, azimuth or elevation:
To wire the board to the incremental encoder, you can use a US Digital part # CA-1094-1 cable assembly. The pins on JP1 match the wires to the CA-1094 connector.
|Following are schematics
and connection information for the LC485-1, RS485 level
converters for incremental encoders. This is a dual
encoder board which can be configured for TTL to RS485 or
for RS485 to TTL levels. Configuration is via a set of 3
jumper pads on the board. Jumper Pad W12 to Pad W13 for TTL to
RS485 (using board at the encoder), or jumper Pad W12 to
Pad W11 for RS485 to TTL levels (using board at the
The board has two sets of connections to wire to the incremental encoders. Use the J5 connections for the elevation encoder, and J4 for the azimuth encoder. The J2 RJ45 connector is only used for connecting the board to the controller and it is recommended to leave this connector off the board if the board is to be used at the encoder end of the line. This will allow more room for attaching the encoder wires.
Below is a block diagram showing the configuration, and a reduced schematic of the board. A board layout and enlarged schematic is shown HERE.
|The S2 series
encoder is suitable for azimuth or elevation encoding
if driven by suitable gearing. The T2 series
is easier to use for elevation as it is an inclinometer
and will not require gearing (works via gravity rather
than being driven by a shaft).
To order these parts you must work up the part number by combining the options you want. The web page gives all the particulars. For an example, the Azimuth encoder we have used is a S2-2048-B-HS. The part number was derived as follows:
Series =S2, Counts per revolution = 2048, B = Ball
The Elevation encoder we have used is a T2-7200.
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