Calculating RPM for DC Motor with Encoders

Using Arduino Motors, Mechanics, Power and CNC
1

I recently started to play with some simple DC Motors with Encoders with the ultimate goal of doing some speed control. I wrote a small program that counts the pulses based on the rotation. For this I'm using this DC Motor that I recently purchased. From the image description given, it says that

The Motor turns one turn output, 11 signals

What does that mean? I',m not sure how to write some logic to calculate the RPM of the motor. Any clues where I could get started? Here is what I have tried so far! Scroll to the bottom of the page!

2

Who knows? Its not exactly a datasheet is it?

Is the 11 the pulses per revolution for one of the signals? Sounds unlikely as these motor-shaft
encoders are usually something like 4 or 6 pole magnets and two Hall switches.

It might mean 12 transitions per revolution per signal (6 pole magnet), or even 11 pulses (11 pole
magnet - as I said unlikely).

You either buy this and measure it yourself, or find a product with better written specs.

3

Ok I get that it is a shitty spec from which one could infer very less.

How about this motor here? Based on what parameters could I understand the RPM?

4

"979.62 counts per revolution of the gearbox’s output shaft" means exactly that.

Simple algebra:

revolutions         counts           seconds        revolutions
------------   ==  --------    X    ---------   X  -------------
   minute           second           minute            count

So rpm = counts/second * 60 / 979.62

5

Cool! I got that working. I'm sure there should be some standard library that does this. Is there one? Any ideas? Just want to benchmark against what I did!

6

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.