Infrared Fork for Disk Speed Sensing

I made a wooden infrared fork for sensing the sync holes in the disk. It is a piece of 1x2 with the center sawed out. It works fine, but the bottom is too weak, so it is strapped together with a tie rap. It is held in place with a spring made of metal plumber's strapping. I also found that I wanted to adjust it too far from dead center, so the height needs adjustment with a shim. All crude but effective. I am thinking about redoing this in metal. The electronic elements are a high-output infrared LED and a phototransistor sold as a pair at RadioShack. I may yet go to a QSE156 detector with logic output, as suggested in the club literature.

Mechanical TV speed sensor IR fork

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