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Electronics => Beginners => Topic started by: nForce on January 18, 2019, 08:11:39 pm

Title: Magnetic absolute and incremental encoder
Post by: nForce on January 18, 2019, 08:11:39 pm
I would like to know how does it work the magnetic absolute encoder and incremental one? Not the optical one.

I have these 2 signals (in attachment) from the incremental magnetic encoder. How would I calculate the speed of the motor?

Thanks.
Title: Re: Magnetic absolute and incremental encoder
Post by: ataradov on January 18, 2019, 09:06:04 pm
This is the same as optical encoders work.

The speed regardless of the direction (assuming that direction is constant) - just use any channel and measure the frequency (number of edge transitions in a unit of time). The RPMs are proportional to that value. Exact coefficient depends on the overall mechanical design of the system.
Title: Re: Magnetic absolute and incremental encoder
Post by: nForce on January 18, 2019, 09:54:07 pm
Ok, in my case it's:

(12.02 kHz * 60)/1024

From where do we get that 60 and 1024?

Thanks ataradov  :)
Title: Re: Magnetic absolute and incremental encoder
Post by: ataradov on January 18, 2019, 10:01:12 pm
1024 looks like the number of edges per revolution. Assuming you are counting only rising or falling edges, that would make your encoder to be 4096 steps/rev, which is pretty standard.

Where does 60 come from, I have no idea. Do you have any sort of gearing between the motor and the encoder?

In your case, if you count N pulses per minute, then RPM = N / 1024, since 1024 pulses constitute the full rotation.
Title: Re: Magnetic absolute and incremental encoder
Post by: rstofer on January 19, 2019, 04:33:14 am
kHz is in seconds, RPM is in minutes, 60 shows up in there somewhere.
Title: Re: Magnetic absolute and incremental encoder
Post by: ataradov on January 19, 2019, 04:35:18 am
Yes, that makes sense :)