‰  NOW 40 WPM  ‰  TEXT IS FROM JANUARY 2017 QST  PAGE 47‰
PANEL.  THE CIRCUIT BOARD MOUNTING POSTS WERE SECURED WITH EPOXY TO THE
BACK OF THE FRONT PANEL.  THIS GAVE ME A BIT OF WIGGLE ROOM TO MAKE SURE
EVERYTHING ALIGNED PROPERLY.  RASPBERRY PI ADDING DIGITAL SMARTS TO AN
EARLY, DUMB VERSION OF THE MOTO MAST CONTROLLER SEEMED LIKE AN EXCELLENT
OPPORTUNITY TO BECOME FAMILIAR WITH THE RASPBERRY PI STARTER KIT.  I
ELECTED TO USE THE LINUX BASED RASPBIAN OPERATING SYSTEM AND PYTHON
PROGRAMMING LANGUAGE THAT CAME WITH THE 

OF EITHER 8 INCHES OR 6 INCHES OF MAST TUBING OVERLAP AT MAXIMUM EXTENSION
BY OPTIONALLY SHORTING PINS 6 AND 7 ON THE CONTROL CABLE.  THERE IS A
SINGLE LIMIT SWITCH AT THE BOTTOM.  A 4PDT SWITCH S1A AND S1B REVERSES
POLARITY TO THE DC MOTOR FOR UP/DOWN CONTROL.  S1C SWITCHES IN THE CORRECT
SET OF LIMIT SENSORS, WHILE S1D LETS THE RASPBERRY PI KNOW WHETHER THE MAST
IS GOING UP OR DOWN.  IN A REDESIGN, I WOULD REPLACE S1 WITH A HEAVY DUTY
4PDT RELAY.  THERE IS QUITE A BIT OF CURRENT FLOWING THROUGH THE FRONT
PANEL MOUNTED SWITCH IN THE PROTOTYPE.  ELECTRICAL TRANSIENTS GENERATED
WHEN THE MOTOR IS STARTED AND STOPPED ALSO CAUSED MANY PROBLEMS.  THE
RASPBERRY PI WOULD FREQUENTLY CRASH IN EARLY VERSIONS.  IN ADDITION TO
IMPROVED BYPASS FILTERING, A SOFT START CIRCUIT USING A HEXFET POWER
SEMICONDUCTOR WOULD BE A WORTHY ADDITION, AND PROBABLY EXTEND THE LIFE OF
THE MECHANICAL ASSEMBLY AS WELL.  MOST OF THE ELECTRONICS ARE ISOLATED FROM
THE MOTOR DRIVE CIRCUITS.  THE USE OF A PHOTO COUPLER ISOLATES THE SENSING
AND CONTROL CIRCUITS FROM THE POWER SWITCHING RELAY.  WHEN SWITCH S3A IS
CLOSED IN THE RUN POSITION K1, POWER RELAY COIL CURRENT FLOWS THROUGH THE

THE MOTO MAST CONTROLLER THE SHACK BASED MOTO MAST CONTROLLER ALLOWS THE
OPERATOR TO RAISE AND LOWER THE ANTENNA MAST AUTOMATICALLY.  THE PROJECT
INCLUDES A RASPBERRY PI MICROCOMPUTER AND LCD DISPLAY TO SHOW ANTENNA
HEIGHT AND MOTOR SPEED IN REAL TIME.  FINAL VERSIONS OF THE FRONT PANEL AND
CIRCUIT BOARD WERE SOURCED QUITE INEXPENSIVELY FROM PROTOTYPE FABRICATION
SHOPS.  THE RESULT IS A PROFESSIONAL LOOKING PIECE OF GEAR THAT FITS NICELY
INTO THE SHACK SEE FIGURE 5.  WITH THE MOTO MAST CONTROLLER AND
COMMERCIALLY PURCHASED ROTATOR AND CONTROL, I HAVE AN ANTENNA SYSTEM THAT I
CAN MOVE UP, DOWN, AND ALL AROUND FROM THE COMFORT OF MY CHAIR.  LIKE THE
MAST ASSEMBLY, THIS IS A PROOF OF CONCEPT PRODUCT, AND THERE ARE
IMPROVEMENTS I WOULD MAKE IN A REDESIGN.  ELECTRICAL DESIGN  THE MOTO MAST
HAS THE MOTOR AND SENSORS AT THE BUSINESS END OF THE ANTENNA, AND A CONTROL
BOX IN THE SHACK.  I USED IDENTICAL CABLE TO THE ONE USED FOR THE ROTATOR.
THE CABLE CONNECTS BETWEEN THE WINCH HOUSING AND THE CONTROL BOX WITH
STURDY CIRCULAR AMP BRAND CONNECTORS.  THE ELECTRICAL SCHEMATIC FOR THE
ENTIRE SYSTEM IS AVAILABLE ON THE QST IN DEPTH WEB PAGE.  THE WINCH BOX
CONTAINS THE ANTENNA BASED WIRING.  THE ROTATION SENSOR PROVIDES A SIGNAL
FOR EACH TURN OF THE MOTOR SHAFT.  UNDER LOAD, THE SHAFT TURNS ABOUT 140
RPM.  THERE ARE TWO MAGNETIC LIMIT SWITCHES AT THE TOP TO ALLOW SELECTION
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ