Cost Effective Speed Measurement using Optical Method for Belt Conveyors

Abstract

Objectives: The aim is to replace the current shaft encoders with a non-contact and cost effective optoelectronic type of speed measurement in the conveyor setup. Methods/Statistical Analysis: There are several methods by which the RPM of the motor can be measured. Existing conveyors uses Shaft encoder for measuring the speed of the conveyor. The main drawback of these encoders is, they are used in contact with the conveyors. This reduces the lifespan of the conveyor belt because of wear of the belt caused by the contact of the encoder wheel. Findings: Initially, different types of encoders were studied and magnetic encoders placed on the motor shaft were found as the right choice, but it was found to be costly. On the other hand, IR emitter and receiver when placed opposite to the rotating disk that contains alternate black and white patterns were found effective in measuring the roller speed. The alternative black and white coloured pattern was chosen because of the property of IR Light to be absorbed by the black region and to be totally reflected by the white surface. It is also inferred from the experiment that the error percentage of the mouse sensor was negligible when the air gap between the IR LEDs and the pattern is less than 20 mm. Application/Improvements: All earlier available encoder devices were in contact with the conveyor setup in one way or the other and are expensive. However, the proposed idea of using IR LEDs to replace the encoder for speed measuring is both contactless and cost effective solution. Placement of suitable lens in front of the IR emitter and receiver will increase the measuring distance without compromising on the reliability of the conveyor speed output. Keywords: Conveyor, Infrared Emission, Optoelectronics, RPM, Shaft Encoder, Speed Measurement