EP3 - Mini Lathe Upgrade - RPM Sensing & Motor Block Finalization - Brushless Conversion How To

In this episode I am doing tests to see what sensor configuration is practical for monitoring the motor. After that I also will complete the installation of the motor block with all the necessary sensors in place.
This is episode 3 in a series of videos where I am endeavoring to upgrade my mini lathe.

[@brianpeers]

Thanks for sharing your brushless motor retrofit project with us.
Those motors interest me as to their potential as a replacement for various devices with the added benefit of speed control but they are still quite expensive just to have an introductory play with. I’m in New Zealand hence the expense.
Speaking of which, your accent is very Kiwi. Am I right?

[@ForOurGood]

Hi Brain, thanks for taking the time to comment, and I am glad you liked the series. So far that motor has worked out pretty nicely, and your right, it does seem suitable for a good range of projects. It is not super powerful by any means, but the big shaft and strong mount makes it ideal for medium scale devices. Not a Kiwi, though I have had a number Kiwi acquaintances during my younger working years, I am actually originally from the other side of the pond, though not lived there for a very very long time now.

[@19mati67]

You should need only the chuck rpm, why do you care about the motor's rpm?

[@ForOurGood]

Simple answer is, that it was an easy way to obtain more frequent and accurate RPM updates even at low speeds. Possibly I could have added a more complex arrangement to the chuck to achieve the same, but I was not confident given the lack of space. The simple chuck RPM sensor I installed only gives a single pulse per revolution sensing, this could only give 1 pulse each second at 60RPM, but this is way too slow for what I need. In the end I use both sensors to detect the current gear state, information both displayed to the UI and used in the speed control logic. Having a faster rate of RPM update is also obviously nice for the UI, allowing for low lag and a consistent display refresh. But I also need a fast low lag RPM update for the automatic speed control logic, as well as the logic I am using to detect a stall for auto-shutdown. Obviously there are many ways to achieve the same, but this worked out ok for me. Thanks for the question!

[@19mati67]

@@ForOurGood But the bottom line, is material cutting RPMs, that is what matters. That only can be had, at the spindle. It could be at the end of the spindle , where the gears are located.

[@ForOurGood]

@@19mati67 Actually for this lathe the spindle and motor speed are always mechanically locked together, there is no way it can slip. So as long as you know the gear ratio you can calculate chuck speed from the motor. This is what I am doing.