This document discusses an optical encoder which converts rotational motion into an electrical signal. It consists of a light emitting diode (LED), slotted disk, and phototransistors. As the disk rotates, light pulses from the LED pass through its slots and are detected by the phototransistors, generating a sine wave. This wave is converted into a square wave and measured to determine pulses per revolution and revolutions per minute (RPM) using a LabVIEW program, allowing rotational speed to be monitored.

1. 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)

2. Introduction
An optical encoder is a complex system
which converts a mechanical rotary
motion (angular position or speed) into
a usable electrical signal.

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

6. 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 wave
which corresponds to the flashing light
pulses from the LED. The sine wave is
then converted to a square wave into
DAQ/NI ELVIS II.

7. 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 one
complete 360 degree
Electrical(not mechanical)
square wave
from an encoder.

8. 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.

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

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

12. 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.