Patent ID: 7534069

Claim:
A programmable boat lift system having a single motor, comprising: a) a single first cable extending up from one end of a first boatlift cradle, and down to an opposite end of the first boatlift cradle, the single first cable being attached to a shaft therebetween, the shaft being attached to the motor; b) a single idler sheave having a plurality of holes for the transmission of light, said idler sheave constructed to engage the single first cable and to rotate on an axis as the single first cable moves across said idler sheave; c) a quadrature encoder having two pairs of IR transmitters and IR receivers, said encoder placed over said idler sheave, said two pairs of IR transmitters and IR receivers being set apart about 165 degrees relative to said axis of said idler sheave; d) said IR transmitters transmitting infra red light through the holes in said sheave and said IR receivers receiving said infra red light so that said encoder produces an electronic output signal in proportion to the number of rotations of said sheave, and in proportion to the distance the single first cable travels over said idler sheave, as the single first cable moves across said idler sheave; and e) an electronic control circuit having a microcontroller, an in-circuit programming header; and a motor control circuit, said control circuit programmable to use said output signal to infer the exact position of the single first cable and the boat lift cradle without the requirement of a limit switch.