encoder to rpm calculation


Thread Starter


hi guys,

I'm still very new to optical encoder, can you guys please tell me how to convert the paulse to RPM, velocity and acclerations?

the device i use is as follows:
DC geared motor with 65:5:1 ratio
motor no load speed 59 rpm
optical encoder counts 500ppr

lastly can you guys also tell me what is those base 2 singnals for?

Where is the encoder, on the back of the motor or tied to the output shaft of the gearbox? It makes a difference in the calculation...


the encoder is couple directly to the rotor of the motor. NOT on the the output shaft of the gear box
For proper output shaft rpm you need to base your calculation on a fixed time base, I have done this before on a small plc using a fixed time interrupt program. Here is an example using a fixed One seccond Interrupt.
Output RPM = ((Pulses Recieved in 1 sec * 60) / PPR) / Gear Ratio

As for Accel and Decel you can store the result of your calculation and every time you update, check weather the new RPM is greater / less then the last value.

By this I assume you mean the A & B signals which are the output of an incremental encoder, these signals are normaly 90' out of phase with each other so as to provide direction information i.e. A before B or B before A.