This is an under-speed sensor module that provides an audible warning and signals output when the speed of a machine is below the set point. The module can be used in applications such as Engines, Machines, Sports machines, Fitness Equipment, Speed of the machine or engine can be detected using a magnetic pickup sensor. The project can be used in many applications where an under-speed monitor is important. The project is based on the LM2907 chip which works as a frequency to voltage converter, interfacing of magnetic pickup as shown in the figure below. A typical magnetic pickup for automotive applications will provide a thousand pulses per mile so that at 60 mph the incoming frequency will be ~16.6 Hz.
Under Speed Warning Alarm for Magnetic Pickup sensor – Frequency Controlled Switch – [Link]