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How to count rpm?

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Qasim Khokhar

Qasim Khokhar

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is there any module for this purpose kindly help me i am not an electrical engineer.

Thanku
 

Re: How can i count RPM ?

Can you give us more information? RPM of what? How accurate? What is your budget?
 

Re: How can i count RPM ?

If you mean to find the alternator or Induction Motor rotation speed in RPM...then use the following formula.
Ns = (120 xf) / P
Where
Ns = Synchronous Speed in RPM
f = AC Frequency..may be 60 or 50 Hz
P = Number of Poles.
Thanks
 

Re: How can i count RPM ?

Use a tachometer, it is easily available in the market
 

Re: How can i count RPM ?

i want to make it with 8051 so kindly guide me ...

Engr Mic G said:
If you mean to find the alternator or Induction Motor rotation speed in RPM...then use the following formula.
Ns = (120 xf) / P
Where
Ns = Synchronous Speed in RPM
f = AC Frequency..may be 60 or 50 Hz
P = Number of Poles.
Thanks
Click to expand...
 

Re: How can i count RPM ?

dear brother
your question isn't clear, of which thing you want to count RPM,

e.g RPM of motor, engine, generator. etc
 

Re: How can i count RPM ?

ANY object? A bicycle wheel is quite different from a jet turbine which is quite different from dentist's drill. If you have a specific thing in mind, tell us. There is no universal answer.
 

Re: How can i count RPM ?

Ohhh yapp :roll: rotation of bicycle wheel


barry said:
ANY object? A bicycle wheel is quite different from a jet turbine which is quite different from dentist's drill. If you have a specific thing in mind, tell us. There is no universal answer.
Click to expand...
 

Re: How can i count RPM ?

Qasim Khokhar said:
Ohhh yapp :roll: rotation of bicycle wheel
Click to expand...
The easiest way to do that is to buy a magnetic sensor that is used by commercial bike computers. It is a reed switch that closes every time a magnet on the spokes passes by. Use the reed switch to make a logic signal that pulses every time the switch closes. Connect those pulses to the 8051 and meausure the time in microseconds between pulses using an input capture peripheral. From that it is easy to calculate the RPM.
 

Re: How can i count RPM ?

As Tunelabguy said before, you can also use a Hall Efect sensor, of course you must have a magnet on some place of the wheel, there are many types of Hall Efect sensors, for your application would be better to use one with Digital output. Search internet for Hall Efect Sensors. Yosmany325.
 

Re: How can i count RPM ?

Yosmany325 said:
As Tunelabguy said before, you can also use a Hall Efect sensor, of course you must have a magnet on some place of the wheel, there are many types of Hall Efect sensors, for your application would be better to use one with Digital output. Search internet for Hall Efect Sensors. Yosmany325.
Click to expand...
Magnetic reed switches are cheaper than hall-effect sensors, and don't require any power. That's why they are always used on commercial bike speedometers.
 

use a strobo scope , the chinease one is about 200$ , it can detect speeds from zero rpm to 10000rpm

this device emits light on and off in a very fast way , you vary the nob until you see the motor shaft (appears to be)not moving , and you read the rpm from the device.

very easy to use and accurate , and u can builld ur own ( i have seen similar projects by arduino)
 

As Tunelabguy said reed switches are best cheapest and simplest solution .
 

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