Help please with DC motor control

I already knew about how induction motors work but I did not know that BLDC motors would stall the way you describe. In my experience when a stepper is being stepped fairly fast and enough load is applied to stall it when the load is removed the stepper is likely stay nearly stalled-it just vibrates-until the step frequency is lowered enough and then it will start to step again. So BLDC motors act the same. I should have figured that out. Thanks for pointing that out. Eric

Reply to
etpm
Loading thread data ...

Doesn't work well, because it has zero ability to recover. Once the actual rotor position is significantly different from what your circuit thinks it is, the torque goes essentially to zero.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
 Click to see the full signature
Reply to
Phil Hobbs

In large sewing machines, this is dealt with by unloading the thread upward from a cone-winding, rather than circumferentially from a spool.

One might also adopt an old tape-drive trick, where the unspooled line hangs in a U bend, and the brake on the spool engages only when there's lots of droop in the outfeed. If one ran the line up over a pulley, and sensed downward force on the pulley to release the brake, the spool is stopped any time there's no string tension. String tension causes switch causes brake engagement.

Reply to
whit3rd

Those tape machines used a vacuum to pull the loop to keep it from knotting up. Some 16 mm projectors used a small variac and undersized AC motor with a pulley mounted on a spring loaded arm to keep constant tension on the film. Any variation caused the sound to stutter. I worked with this in a film chain that used RCA TP66 projectors. No tension ran the motor at full torque. Too much reduced it to the minimum. The came in handy when loading a new reel. You could slip the leader between your fingers when slowly letting the arm up to wind the leader onto the reel. Run the nylon cord between some pulleys with a slight groove to keep it centered. Pull on it, and that pulls against the control lever to adjust the motor speed. Stop pulling, and it stops.

--
Anyone wanting to run for any political office in the US should have to 
have a DD214, and a honorable discharge.
Reply to
Michael A. Terrell

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.