Page 36

EDNE MAY 2015

designideas and X2 outputs to an XOR gate, we can double the data rate, though losing directional information. Physical realisation The sensing disk or other surface must have some texture, pattern, scratches, or a brushed finish to get good results for the optical recognition of its surface patterns. The construction below was successfully applied to provide synchronised movement on assembly lines, and for transporters, labelling equipment, and printing on moving objects. Over 100 units were made, and all continue to work well after several years. Other sensor ICs are available which will handle different light sources, outputs, speeds, etc. For instance, the PAN3101 CMOS optical De-embed transmission lines with FIR filters mouse sensor uses SPI, and the PAN101B CMOS optical navigation sensor has both SPI & quadrature outputs. Example schematics for SPI interface The sensors with SPI (or USB using one more IC) interfaces don’t allow us to track every pulse separately as they send packets of data. For hard real time applications, the sensors with the quadrature output are preferable. It would be interesting to build an encoder from a wireless computer mouse; and perhaps even more interesting, using the sensor from a digital caliper, as most of them have an I2C interface. But that’s another story. 35 EDN Europe | MAY 2015 www.edn-europe.com


EDNE MAY 2015
To see the actual publication please follow the link above