YET ANOTHER ANTENNA ROTOR CONTROL

OBJECTIVE

This controller "low-cost" ensures the control in azimuth and elevation of VHF and UHF antennas for satellite tracking or EME.

It incorporates a number of developments carried out in collaboration with F1OAT, F1HDI and F5DJL especially on the absolute elevation solid-state sensor.

It was at the request of Bernt DL7HR and Gunther DL4MEA I finalized this small controller.

Synoptic

The control system incorporates the sensor described in the previous pages

We are for elevation a absolute sensor that just fix on the antennas by a setting at zero degrees.

For information azimuth, we use a potentiometer, for example placed inside many types of commercial rotors.

The originality of the system lies in the fact that both measures azimuth and elevation are digitized in the sensor located in the antennas and transmitted over a serial line two twisted son RS485, up to one kilometre long .

The sensor is powered in 12V by two low gauge wires.

The other wired connections necessary are two or three wires for motors power supply, depending on the motor type, AC or DC..

Accuracy

For the sensor elevation, accuracy reached in theory the tenth degree.

For the azimuth, the measure is a 10-bit analog conversion and would therefore be equivalent.

However, we must rely on the linearity of the potentiometer, which is far from perfect on commercial rotors, and the fact that only part of the potentiometer will be used for 360 degree rotation, which reduces accuracy.

As a result, I have displayed only the degree digit in azimuth, which is more than enough to control antennas on 144, 432 and may be 1296 Mhz.

Controler Schematic

The controller uses a minimum of components around a PIC 16F877.

Two serial transmission lines.

A MAX232CWE for RS232 connection with the PC. Tracking protocols accepted are GS232, EasyCom or Nova.

A MAX483 for RS485 connection with the sensor.

An LCD display standard HITACHI accepting orders on 4 bits format of data.

Four N mosfets BS170 for control relays of the motors : UP, DOWN, LEFT, RIGHT

Four entries for the manual control.

Two entries "SETUP" and "OK" for the azimut calibration procedure.

Other entries on the PIC are "RFU", reserved for future use.

One in particular, connected to a opto-coupler is planned for counting pulses in the case of SPID ROTOR.

Part List

Motors command

Not provided on the PCB, this part depends on the type of used motors.

Four relay with appropriate contacts and a few judiciously diodes connected.

bellow, two examples of connections for CC and AC motors

Azimut calibration

Calibration azimuth

To accommodate the range used by the potentiometer and possibly introduce a stop other than the North stop, a calibration procedure is planned.
It enter in the configuration menus in the power-up time , if the SETUP line is down, switched to ground.
The first request if an west offset, for example 90 for a west stop or 180 for a south stop.
Value entered by azimut keys command
The push "OK" valid entries.

The following message request to position the antenna to stop "counter clockwise" with the manuals azimut keys, then in the position stop "clockwise" to mesure the two extreme voltages for a complete rotation of 360 degrees.

The alignment mechanics antennas being a classic on a mechanical stops.

This calibration must be made at least once.

PCB

Above the PCB sensor and the control card.

CAD by F1TE, a small quantity of PCB are made, professional double-sided, metal holes and silk-screen.

No KIT, only a few printed circuits are available on request.

The relay is left to the initiative of each.

Firmwares

The sensor program is only available in format HEX.

It is the work of F1OAT, F5DJL and F1HDI.

The program PIC 16F877 is the work of yours truly.

It is also available in HEX format but on request, I can provide the source code if you want to make changes or features.

It is written in C compiler PCW of CCS.

All documents can be downloaded in ZIP file

Lucien F1TE