I am trying to customize the normal AC motor in such a way that when it will be connected to computer by using some micro controller (e.g Arduino) its rotation will be calculated. i can measure the rotation speed if i use Hall effect sensor which uses a refrence point to calculate rpm but my problem is i want to get the angular location of rotating shaft in terms of degrees in such a way that when motor will be turned on the one degree change must raise an event or generate a signal in microcontroller. How i can achieve this i searched a bit on it and crawled the following info

Time Synchronization: in this way i will calculate the time taken for one rotation then calculate the time took for knob to move 1 degree. This way i shall start timer and calculate or pridict the knob location. this is good but obviously there will be uncertainty and it will not be perfect or reliable.

Stepper Motor: Using a servo motor increases the accuracy because its moving steps will be counted and known and fixed in 360 degrees. but How i can convert a normal AC motor to Servo architecture i do not like this way.

A Specfific Hardware: Well third approach may be designing a hardware that will be designed to be able to attach with any motor and it will update speed. The Question is does some thing like this exists?

what approach is best accurate and reliable as well as easy to implement for this task. if you have any other idea then i am waiting eagerly.

  • \$\begingroup\$ Google rotary encoder \$\endgroup\$
    – crj11
    Mar 23, 2018 at 20:03
  • \$\begingroup\$ Is there a specific reason you want to use an AC motor? A DC stepper would be more appropriate here. \$\endgroup\$
    – Norm
    Mar 23, 2018 at 21:02
  • \$\begingroup\$ i have to rotate a large propeller hmmm approximately 2 meters long so DC stepper i dont think so will meet the requirements \$\endgroup\$ Mar 24, 2018 at 13:58

1 Answer 1


This web page has a good summary of the options, including their own that they're trying to sell:

  • Hall sensors (can give you absolute position with careful design or multiple sensors)
  • optical encoders (relative or absolute)
  • "Resolvers", which operate by generating an alternating magnetic field and measuring its relative coupling to coils at different angles
  • \$\begingroup\$ Add to @pjc50 answer, GMR angular displacement transducer. \$\endgroup\$
    – AlmostDone
    Mar 23, 2018 at 21:03

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