I've bought a DC geared motor with an optical encoder. The vendor didn't provide specification. I can read MITSUMI M25N-2R-14 2241 and 25GA-370-12V-330RPM on the motor. There are some pages on the internet about this motor with contradicting information that I can't trust. I need to find a practical method to find exact gear ratio and encoder resolution.

enter image description here

I took a picture of the encoder and in a CAD software measured 1 degree the angle between two lines. I'm not sure about accuracy of this method!

enter image description here

I use this code in Arduino:

#include <Encoder.h>

Encoder myEncoder(2,3); // Best Performance     2, 3   intrupt
double Position ;
void setup() {
Serial.begin(250000) ;
Serial.println("Encoder Test.") ;
long oldPosition = -999 ;
void loop() {
long newPosition = myEncoder.read() ;
if (newPosition != oldPosition){
oldPosition = newPosition ;

I can read data from my encoder but how can I use this data?

  • $\begingroup$ I don't know the gear ratio, it makes it hard to check visually. I have another problem with the encoder. it works fine when I test it manually (turning shaft with hand when the motor is off) but shows random pulses when the motor is running! $\endgroup$
    – 2012User
    Sep 19 at 12:01
  • $\begingroup$ oh, looking at the other end! that is right but this a small motor... I will try! $\endgroup$
    – 2012User
    Sep 19 at 19:52
  • $\begingroup$ Welcome to Robotics 2012User. On stack exchange, it is better to edit your question to add information rather than adding comments. Comments are for helping to improve questions and answers, and are distracting, so we try to keep them to a minimum. If all of the information needed to answer the question is contained within it, the comments can be tidied up (deleted). $\endgroup$
    – Ben
    Sep 28 at 15:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.