75 to 1 ratio gearbox for VTR valve control (central heating) for 28BYJ-48

This is a gearbox which I use together with a 28BYJ-48 to turn my VTR valve. A ESP8266 module is used to automate the position or manually set it. 

I use a Wemos D1 mini to move the valve towards the 0% position until the end stop is pressed. Once the end stop is actuated, step counter is set to 0 and the system is calibrated. 

If you are just looking for a gearbox for the 28BYJ-48, feel free to remix the model.

uses standard M3 hex socket screws, 1 x 61805 bearing and 1 x 623 bearing with a 10t85 microswitch.

Use minimum 3 perimeter in the settings and organic supports.

Use a M3 tap to thread the holes to make it easier to assemble everything. Print in PETG if planning to use for a long duration.

Screws needed:
4  pieces of 25 x M3 (can be longer, used to mount gearbox casing to housing)

2 pieces of 3 x 2.5 mm screw (used to mount the stepper motor)

4 pieces of 12 or 14 x M3 screws (used to mount output coupling adapter to shaft coupler)

1 piece of 10 x M3 to keep the 623 ball bearing concentric with the sun gear

More info on how to set up the ESP coming soon on GitHub

EDIT: Added .3MF file to allow easier modification