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Max 100 or anyother number turns Motor

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Full Member level 3
Sep 12, 2014
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I want to build a hardware that turns/rotate only 100 times or any other number, then stop. First thing I thought was using any motor and count its turn with a hall effect sensor. Then turn the motor off as limit is reached. But I'm wondering if there are any other better ways to do such thing ? Or something already built like this and is available to buy ?

If you need to turn something then yes - you need a motor...isn't it obvious?

If you need to turn something then yes - you need a motor...isn't it obvious?

Thats not the question :) But there are many types of motors. Something specially built for this. And it is also possible, someone already has built something like that, that can be purchased. :)

More information is required...
What do you want to turn and how fast?

You cannot simply count turns and stop as this depends on inertia, speed, power , torque.

But you can design a servo to have a controlled velocity profile and position using hall sensors .
Do you want it to stop at same rotor position every time.
DOes that require power to stay in that position?
Is there a lock to prevent free wheeling?

THese and many more questions must be answered for you to define a SPEC and include power , load, speed control profile and position accuracy and perhaps time to target.

Try again.

@shaiko : I do not require very high speed, 100 RPM would do fine. It needs to turn a little socket with no load. The socket is cylindrical shaped and weight less than 50 grams or less.

@SunnySkyguy : There is no lock. I know lock is required to stop it instantly, but thats not the problem if it get like 5 more turns because of speed force or whatever it is called.

I do not know much about power to be in specific words. But lets just say, it should have enough power to get the plastic socket sanded with very little human finger force. Like, you put tiny sandpaper in between index finger and thumb and you put very little force just to get feeling it is getting sanded. Yes it sound crazy, why need specific turns for sanding, but its just for showing how much power is needed.

Accuracy is not important in this case. Also, as far as I know servos are bound to specific angles, they have limits, they cant turn 0 to 360 degree and continue but I could be wrong.

@Warpspeed : Stepper motor is very good but they cost more for this project.

If the motor will run at a constant speed the easiest way is to use a timer. Another fairly simple way is to count the number of brush commutator switches. For a cheap motor this will be 3, so a divide by 300 would be required. To stop the motor rapidly, you could try a brake actuated by a solenoid, or put a short circuit across the motor, or put a reverse voltage pulse on it.

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