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I have made a demonstration video on my simple machine. It do have got a simple universal motor, a speed reducer, and I made some electronics for it that make the system act as a servo motor. The speeds demonstrated in the video are from 8 stitches/min to 540 stitches/min - a factor 68. The response to load changes and small moves are shown as well: What is your controlable speed range of your sewing machine with servo motor? Can you do better or worse? I have seen some recent demonstrations on youtube of industrial sewing machines with servo motors. And I am not that impressed of the speed control I see. For most of them, I see them jump start to a quite high low speed, and I do not like that. I did see this video from 2012 showing a resonable good low speed control, but I am not sure about the max speed and speed range: https://youtu.be/-h5U32SDZ38 Back in year 2012, several servo motor types had an issue, that they were hard to control. These issues were discussed in this forum, and I shall like to link to the four threads I just read about it: https://leatherworker.net/forum/topic/40034-question-about-servo-motors/ https://leatherworker.net/forum/topic/40168-cobra-class-4/ https://leatherworker.net/forum/topic/41483-servo-motor-mod-diy-easier-speed-control/ https://leatherworker.net/forum/topic/41916-having-problems-with-servo-motor-speed-control/ At that time a simple modification to some servo motors was introduced. More US suppliers of servo motors tried to make improvements and contacted their suppliers and manufacturers. I am however not sure, how much change to the designs that were later introduced. Electronic designers of servo motors may have limited knowledge of the needs of a sewing machine operator. Of cause an electronics designer can be incompetent aswell. The discussions here back then indicated, that many leatherworkers like to be able to sew very slow and also fast with the same set up. I think a factor 100 between lowest speed and highest controlable speed should be easy to make for servo motors. It could be from 45 RPM to 4500 RPM. However It seems to me, that most of the servo motors for sewing machines have a range with a factor about 30 only. The pedal construction can also be a limitation. However many leatherworkers were also happy with the motors they had. Others wrote, that they were not aware before the change, that they should like the better control they were able to get.