RPM Hall Sensor for Motor Fan Mount, Speedometer, Arduino

thingiverse

This is a Hall RPM sensor kit for an induction motor. The sensor itself is a KY003 Hall effect sensor board. These output a logic signal when the tip is in the presence of a strong magnetic field. Here is the board and a very nice tutorial on how to use it: https://create.arduino.cc/projecthub/WellTronic/ky-003-hall-sensor-module-6c003a I made a somewhat sturdy mount for the KY003 board and its sensor to attach it to induction motor. I also made a replacement for the original cooling fan for the motor, but this new one has small holes to hold three, 6mm diameter X 4mm thickness, neodymium magnets. I mounted the sensor holder with foam mounting tape, after carefully cleaning the surface of the motor with alcohol (to remove any grease.) I then mounted the new fan, complete with magnets, in place of the original fan. You need to tap the set screw hole in the fan hub for 1/4-20. I glued the KY003 into my holder with silicone chalk to prevent bits of dirt, etc, from interfering with the circuit. It is important to note that the Hall sensor only works when the magnet is oriented in the correct direction. Test the sensor with the magnet, and then _mark_ the side of the magnet that needs to pointing towards the sensor. I used the very well written Arduino library FreqMeasure to read the logic output of the KY003. The FreqMeasure library has a nifty routine (FreqMeasure.countToFrequency) to convert the measurement to Hz. I then changed this Hz reading to RPM by multiplying by 60 and dividing by 3 (three magnets.) Basically, you multiply Hz by 20 to get RPM. https://www.pjrc.com/teensy/td_libs_FreqMeasure.html I should note that this whole set up would also work very well for a speedometer. Mount small magnet on the wheel somewhere, mount the KY003 sensor so that the magnet passes nearby, and "Bob's your uncle". :-)