Encoder - E4P-360-250-D-H-D-B

[spyla]

Hi,

First time mentor. Trying to get RPM from Encoder E4P-360-250-D-H-D-B. looked at two examples, "encoder" and "motor and encoder" rate is defined as different in one it is distance/sec in the other it is deg/sec where as when I click on detailed help for "encoder get" it tells me that rate is pluses in Hz. which is right?

if detailed help is right, then I would need to divide the rate by 1440 and multiply by 60 to get RPM

if it is Deg/sec then I would divide it by 360 and multiply by 60 to get RPM

if it is distance /sec then divide it by (6*pi) and multiply by 60 to get RPM assuming a 6" wheel.

Also we have not been able get the the "motor and encoder" example run properly. I can turn wheel by hand and get values to change but the motor won't turn by Joystick. Only thing I changed on the example was to change open motor to Jaguar. But I can run the motor through the default robot project.

thank you

spyla
team 3616

[Team3266Spencer]

I didnt look up the model but my gut feeling is there are 360 pulses per revolution from your encoder, so you would get degrees per second by calling the rate, what language are you using?

[spyla]

labview, it 4X decoding type, hence 360*4 = 1440

[Joe Ross]

The units by default are cycles* per second. Your encoder has 360 cycles per revolution. It doesn't matter whether you use 1x or 4x decoding, as it takes 4 pulses in 4x decoding to equal one cycle, and everything is normalized to cycles. I think that the LabVIEW library may sometimes use the term pulses or counts, when they mean cycles.

Since your encoder is 360 cycles, one cycle also equals one degree, so you can say that it returns degrees per second, but only for that particular encoder.

There is an option to set the distance per cycle. This will scale both the distance and rate outputs. This is why some of the examples show other units, because they set that value.

By dimensional analysis, to go from cycles per second to revolution per minute, you would divide by 360 cycles per revolution and multiply by 60 seconds per minute.

For rate calculations, it's better to use 1x rather then 4x decoding, as the encoder wheel is more accurate cycle to cycle rather then pulse to pulse.

*Cycle is the term US Digital uses for a complete quadrature cycle. I've also seen people use the term count.

[Alan Anderson]

Using 1x decoding on a quadrature input, the values go 0, 1, 2, 3, 4...

Using 4x decoding, the values change four times as often but by one fourth the amount: 0.00, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50...

You get the same value for the same amount of rotation, just with a different precision.