Howard Dutton and some others are experimenting with the??closed loop stepper motor. The on board motor electronics adds about $15 to the cost of each motor. Early impressions indicate it corrects for missing steps once a rotator?revolution. While this may double motor resolution of a 1.8¡ã step motor to that of a 0.9¡ã (400 step/rot.) motor, it doesn't make real sense. A 200 step motor is a couple bucks less than a 400 and the 400 step motor's resolution is below? is already below the distortion of the atmosphere.
As can be seen in the video this tech seems more important on printers where high frequency changes in direction are required. The only time a stepper driven mount runs like this is during goto where resolution is judged by, is the object in the FOV? While tracking the 400 step motor is running at the 0.375 RPM or 4800 ?steps/minute or 160/second (assuming a GM-8 with 3:1 belt reduction and using 32 ?steps/step). 160 ?steps requires the Teensy 400 to clock 2.5 million cycles between ?steps. Pretty boring work. Its predecessor the Teensy 3.2 only had to count to 0.5875 million.
