Optical Encoder

Group MembersGroup Members

Hasnain Nazir(ME23)Hasnain Nazir(ME23)Mubashir Ayub(ME27)Mubashir Ayub(ME27)

Arif Wahid(ME25)Arif Wahid(ME25)Assadulllah(ME80)Assadulllah(ME80)

Introduction

An optical encoder is a complex system

which converts a mechanical rotary motion (angular position or speed) into a usable electrical signal.

An encoder is a photoelectric emitter receiver pair looking through a slotted disk.

The encoder operates on the principal of optics. Light from the LED passes through the disc, the mask, and into the photo transistors.The photo transistor outputs a sine wavewhich corresponds to the flashing lightpulses from the LED. The sine wave isthen converted to a square wave into DAQ/NI ELVIS II.

Pulse rate or Pulses per Revolution is defined as the number of physical lines and corresponding spaces on the code disc.

A pulse is equal to onecomplete 360 degree Electrical(not mechanical) square wavefrom an encoder.

A LabVIEW Measurement of RPM

We can use the Pulse Measurements.vi

to measure the period, pulse duration, or duty cycle from a waveform array.

We can convert the period measurement to revolutions per minute by inverting theperiod to get frequency and multiplying by 60 to get rpm. For scaling, divide by 1000 toget krpm.

Use the DAQ Assistant to collect 1000 V samples for the tachometer graph and provide an input signal array for the Pulse Measurements.vi.

Run this VI and take your motor for a spin. See and hear how responsive the motor is to a rapid change in the rpm setpoint.