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Tom, W2DRZ has developed a new antenna controller. This interface can be driven by potmeters, incremental and absolute encoders.  The interface can be driven by both F1EHN and Nova software. You can find a description of the controller on Tom's website : http://www.w2drz.ramcoinc.com

 W2DRZ_eme_Controller_002.jpg (62983 bytes) picture ON4BCB  

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We choose for the US Digital A2 Absolute encoders. For the X ( Azimuth ) axis the encoder is mounted on the gearbox output shaft, so directly under the antenna. For Y ( elevation ) we chose for the US Digital A2T - S - DD . This is a double damped Inclinometer with a precision of 0,1 degrees. The Inclinometer is mounted directly on the antenna backplate.

We decided to build a H-bridge, using N Fets to drive the motors. N Fets don't have to decipate to much power, and are ideal to make solid state relays. Also, a motor brake is integrated, ones the controler indicates the final position has been reached, the motor will brake. Using PWM, it is possible to control the speed of the DC motors. Below is a picture of the power supply, controlling the motor and you see the back side of the W2DRZ controller. . In the same chassis, all other low voltage power supplies are integrated.

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Walter, ON4BCB builded a nice PIC processor based speed control in between my W2DRZ controller and the H-bridge. W2DRZ does not implement any speed control in his interface. A speed control is very handy, since the tracking has to be low speed for best accuracy, but when the antenna has to travel from E-W or W-E, it can take up to 5 min. The H-bridge is controlled by a IC bus interface. It accepts speed control and stop functions. Walter has build an interface, that accepts the control of the DRZ interface. When the movement of a certain position takes longer than 5 sec. ( which is longer than a normal tracking control) it will move the PWM of the H-bridge to a full speed function. The antenna will travel high speed to its target position. A second function is a STOW position. On the antenna we installed a wind speed meter device. Ones a certain windspeed is been measured, the antenna will go into STOW position, which is 90 Elevation. This will take the torque away from the AZ motor, and the 90 EL position takes a lot less wind load to antenna and tower. The STOW control will receive an auto reset after 5 min. 

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