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G Servo Adapter


Inspired by Dagnall's design to use a servo as point motor.


The adapter measures only 18mm in height, and is designed for outdoor use.
All used screws should be of stainless steel or brass.
The electronically, cable, connection should be corrosion free.



The servo adapter is a 'one side' design. Select the wanted side before generating the STL file:


Change this line in servo-bottom.scad and servo-top.scad.



The mounting side can be selected in the SCAD file.
Three tiny holes are for draining the condense water.


The top includes a water drip for cable and rack outlet.

Rack and Gear

The rack can be used for the full 180° servo movement, but for standard LGB/Piko there is only need for 7.5mm which resembles a movement of 120°
The type of rack can be selected in the scad source: THIEL or LGB.
The LGB type hook is positioned 2mm lower on the rack.


  • Tie connection: M3 x 8mm stainless steel, raised head with flange
  • Cable clamp: M2 x 8mm stainless steel, flat head self tapping
  • Top connection: M2 x 16mm stainless steel, flat head self tapping



  1. Thread M3 in the tie connectors.
  2. Put the gear on the servo, and fix it with the small screw.
  3. Set the servo in the middle position. (approximately 90° of 180°)
  4. Set the lever in the bottom and move it approximately to the middle position.
  5. Press the servo in the mounting.
  6. Cable connection depends on available infra structure. The clamp can be used to fix it.

Servo types

servo-padheight.jpg The servo pad thickness depends on the used type/brand. (MG servo's are recommended.)
Check the source for setting the right parameter value: (Note: This value includes the 2mm mounting wall.)

SERVOPAD=4.8; // MG90S (Use 4.5 for SG90)


Some hints for printing based on Ender 3V2 and Cura.


Parameter Initial Regular
Fanspeed 0% 25%
Build plate 75°C 70°C
Hot-End 240°C 230°C
Speed 15 40

For better adhesion, to prevent warping, '3DLac' has been used.

HALL Sensor

A Hall sensor can be used for detecting the rack position. (approximately)
The GCA217 PCB fits under the servo with the right settings in the SCAD file.
In the Rack there is a magnet holder in which fits the following type:
Bar magnet Ø 3,0 x 5,0 mm N42 Nickel
The sensitivity can be adjusted by moving the magnet towards or away from the rack.

The GCA217 has a bug in the labeling. It should be:
Hall-1 is for the Right Type, and Hall-2 for the Left Type case.
The Hall sensor can be set in the Switch Properties for both directions. One of which should be set invert.


Heavy rain and hail swamped the 10cm ballast, and put the Servo Adapter for a short time under water:
But, the Servo did survive.

User waterproof servos like MG90S:

Used for the rack and gear.
robvrs/servo-adapter-en.txt · Last modified: 2021/09/07 16:31 by smitt48