Miniature position encoder with radially non-aligned light emitters and

Abstract

A miniature position encoder (10) provides means for transducing angular changes in shaft (60) position to an electrical output representing the Gray code. The miniature position encoder (10) comprises an annular housing (12) having an aperture (14) with a bushing (20) disposed therein opposite an open end (18) of the housing (12), a plurality of light emitting diodes (50) disposed in non-linear alignment in a substrate (40) mounted adjacent the bushing (20), and a metallic shaft (60) journalled within the bushing opening (15) and having a metallic logic disk (70) secured at one end, the logic disk having a plurality of radially spaced and angularly limited openings representing the Gray code. A window disk (110) is mounted within the housing cavity (28) and adjacent the logic disk (70) for the purpose of restricting the amount of light emitted by each of the light emitting diodes (50), and a plurality of phototransistors (100) are mounted upon a substrate (90) positioned at the open end (18) of the housing and adjacent the window disk (110), with a cover (120) enclosing the open end of the housing. Rotation of the shaft (60) effects rotation of the attached logic disk (70) which modulates the light passing through the openings within the logic disk, whereby the Gray code is transmitted as an eight bit parallel output code received by light receptors (100). The Gray code data may be transmitted directly to a microprocessor, or transmitted to an exclusive OR gate circuit for conversion into digital binary code.