This ASCOM driver is for a stepper motor based helical focuser. The motor drives the focuser via a timing belt. The focuser itself is extended with a 3D printed toothed belt wheel. For my prototype I use the ZWO Helical Focuser 1.25'' with T thread.
Motor used: NEMA 11 Stepper motor, 52mm length, 200 steps and 5mm shaft.
Belt: GT2 with 125 teeth.
Control electronic: Arduino Uno with CNC shield.
Stepper driver: TMC2130, standalone mode with 16µ steps, interpolated to 256µ steps.
The Arduino and the CNC shield are 12V powered, the stepper is connected to the Y driver.
Arduino Uno based controler. Firmware for this setup is part of this repo.
Robust alu housing, sitting on a GP dovetail (via 3D printed mount).
The focus motor is controlled via a simple serial protocol, 9600 baud:
Command Response Description
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ID: FOCUSER# Device identification
TRxxx: 1# Move right xxx steps
TLxxx: 1# Move left xxx steps
ST: 1# Stop the current movement
MV: 0# or 1# #1: Rotator is moving, otherwise 0#
MOFF: 1# The motor is disabled after movement
MON: 1# The motor is always powerd
PO: xxxx# The (relative) position is reported
After powerup the focuser does not move, the position is reportet as 0 and it can be moved between to negative (left) or positive (right) direction. The firmware does not restrict the amount of movement.
For usage with the PHD2 guiding software a ASCOM focuser client application is added into this repository.