Optical digital sensor for crane operating aid

In a crane including a first portion and a second portion, said portions being operably moveable with respect to one another, a crane operating aid comprising:

• detector means associated with one of said portions and including an array of light emitting elements;
• encoder means associated with the other of said portions and operative to optically impart digitally encoded information to said detector means representative of the displacement between said portions;
• means operative to energize a series connected plurality of said light emitting elements;
• a fault detection circuit operative to maintain a constant current through said series connected plurality of light emitting elements and to generate a fault condition signal operative to deenergize all of the light emitting elements within said array upon detecting a failure of any one of said light emitting elements;
• and
• operator interface means operative to receive said digitally encoded information and generate a sensible crane condition signal as a function thereof.

In a crane including an upper mounted for rotation upon a lower and a boom pivotally mounted upon said upper, a crane operating aid comprising:

• a first absolute encoding digital optical sensor operative to monitor the slewing angle between said upper and lower and to generate a slewing angle data signal as a function thereof;
• a second absolute encoding digital optical sensor operative to monitor the luffing angle between said boom and upper and to generate a luffing angle data signal as a function thereof;
• and
• operative interface means operative to receive said signals and to generate sensible crane condition signals as a function thereof;
• each said sensor comprising
• detector means including an array of light emitting elements;
• encoder means operative to optically impart digitally encoded information to said detector means representative of the displacement therebetween;
• means operative to energize a series connected plurality of said light emitting elements;
• and
• a fault detection circuit operative to maintain a constant current through said series connected plurality of light emitting elements and deenergize all of the light emitting elements within all of said sensors upon detecting a failure of any one of said light emitting elements.