Anonymous
Anonymous asked in Science & MathematicsEngineering · 1 decade ago

How can I count the number of rotations my DC (direct current) motor makes? What tool can I use to count...?

accurately? I have a DC motor kit that I building and testing and I want to count the number of rotations it makes? Please help. THANKS.

5 Answers

Relevance
  • Anonymous
    1 decade ago
    Favorite Answer

    You want to use something called an encoder. The encoder has a series of slotted rings that pass between an optical detector and a light source. The on-off sequence of the slots interfering with the light source can be read as angular position of the motor shaft. This is the most accurate method.

    If you don't want to bother with an encoder, you can also measure voltage across the motor. This 'back emf' is proportional to rotational velocity. Send different voltages to the motor and find the proportionality with rotational velocity (i.e. how many Volts will give you a certain rpm). Once you know rpm in this manner, integrate in time to find rotations. Integration can be done with a computer program or with an analog op-amp circuit (look it up).

    • Login to reply the answers
  • 1 decade ago

    I think you really want to measure the speed of your motor. The total number of revolutions will depend on how long you let it run.

    To measure the speed (revolutions per minute) of a small kit built motor you would get the best results if you can borrow an optical tachometer. They aren't that expensive but still cost too much to buy for one project. If you, or someone in your family, know someone that works in maintenance, a mechanic or industrial electrician for example, they should be able to help you out.

    • Login to reply the answers
  • 1 decade ago

    Well, if i"m right you want to find out how many rev/minute your home made motor runs, right?

    Well, then you need then a precision tool that's called Turometer, or speedometer which measures with great precision what's the speed of your engine. It has a rubber tip and a watch(or display-if modern) indicating the revs it receives from the engine's shaft through the rubber tip. It's quite small, and can be weared into the pockets of your coat.

    Dfriend :)

    • Login to reply the answers
  • Anonymous
    1 decade ago

    A direct current motor speed is relative to the amount of voltage. You can use a lower voltage that you can count the revolutions by eye, increase the voltage slightly and measure again, repeat. You should be able to see a trend of increased rpm to voltage start to set up. Then you can extrapolate.

    Source(s): I think
    • Login to reply the answers
  • How do you think about the answers? You can sign in to vote the answer.
  • 1 decade ago

    You can use either Mechanical or Optical techometer. Or Stroboscop to count the RPM of DC motor.

    • Login to reply the answers
Still have questions? Get your answers by asking now.