Introduction
We needed to determine the phase of the motion of an actuator relative to the sinewave driving it. The following circuit detects the sinewave zero crossing, then produces a light flash some time later. The delay time at which the strobe shows the actuator crossing zero (when viewed under a dissecting scope), compared to the period of the sinewave, yields the phase.
The Circuit
The following image shows the yellow LED near the actuator sphere.
