Reed switches in Gear speed and direction sensing
Mechanical machinery always have a set of manual controls that not only direct the machinery between a forward and reverse operation but also change the speed of the operation. This sort of manual positions systems need to be translated to a digital form for microprocessor based decision making. Such machinery always have multiple gear mechanism that can be sensed using reed switch based products such as gear speed sensors to feed information to the central control based on the machine operators control decisions.
Miniature ferrous part detection sensors are positioned near the gears to sense the speed of rotation. Reed Switch based sensors have very high sensing speeds and can sense up to 30,000 RPM. Special ferrous part sensors which can sense gear direction are built with two reed switches and a biased magnet and combining this system with a D-Flip-flop for quadrature sensing. One of the reed switches is connected to the D input, and the other clocks the input. This way, one direction is differentiated from the other by monitoring the output Q of the D-FF.