AstroTrackerHD Prototype 4

May 4, 2019 - Reading time: 2 minutes

AstroTrackerHD Prototype 4 in testing, with pics. (HD = harmonic drive, which is a high-precision, high-torque, zero backlash gear set. See: I did some code cleanup and refactoring for version 4.0.7, and added the ability to adjust the speed in small increments and save the speed values to eeprom. I have a couple posts on this earlier in the year, but if you haven't seen them: AstroTrackerHD is my project to build a very accurate star tracker using a NEMA 17 stepper, 139:1 ratio planetary gear feeding a 100:1 ratio harmonic drive. I'm running updated software in this one, and I'm in the process of 3D printing some brackets for the stepper. 

Harmonic Drive testing

January 21, 2019 - Reading time: ~1 minute

Star Tracker Build: the 100:1 reduction Harmonic Drive gearhead arrived today, and I'm planning out the mechanics for the direct drive train and structure for a case (3D printing a prototype case that will hold everything together tonight).  Harmonic drives are the way to go if you're looking for extreme precision, zero backlash, and just plain cool technology: I will be using the original iOptron CEM25P saddle for testing, and the threaded holes in the harmonic drive line up neatly. Gearhead specs here: 


Direct-drive Star Tracker Prototyping

January 14, 2019 - Reading time: ~1 minute

Electronics project for the day: prototyping the drive system for a direct-drive star tracker. This will be driving a 100:1 ratio Harmonic Drive gearhead. For this test I'm using a NEMA 11 stepper motor, also geared down, and a cheap A4988 stepper driver, but I will be experimenting with others.