A simple device used for measuring the speed of the wind. When built with a ceramic ball bearing it can measure extremely low wind speeds due to the low friction.
It is important that the screws holding the ball bearing, is exactly 15 mm long, since the tip of these screws will exactly secure the ball bearing.
Both the magnets and the hall sensor can be fixed with superglue. After the hall sensor has been glued inside the cavity in the base with superglue, it can be sealed to make it even more watertight with hot glue, just make sure to cut any extra hot glue with a sharp knive, no nothing sticks up from the base.
The base is made with a hall sensor, it is important that one of the magnets is installed in reverse direction of the other, so one of the magnet has a northpole towards the hall element, and the other magnet has a southpole towards the hall element.
Additional things needed:
1 x ball bearing of type: 608 ZZ, size: 8 x 22 x 7 mm, a ceramic version is preferred, such as https://www.ebay.com/itm/608-ZZ-Deep-Groove-Ceramic-Ball-Roller-Miniature-Bearings-Frictionless-Skate/143211711365?hash=item2158154b85:g:g4AAAOSwGoJcruK8&frcectupt=true
1 x Hall element sensor IC US1881 (Latching type) https://www.ebay.com/itm/10pcs-U18-US1881-OH188-1881-hall-element-sensor-switch-IC/201443658376?epid=881433578&hash=item2ee6fa4a88:g:pZIAAOxy-WxTA2zy&frcectupt=true
2 x Cylinder Disc Magnets 8 x 3mm Neodymium https://www.ebay.com/itm/20Pcs-8x3mm-Rare-Earth-Super-Strong-Disc-Round-Cylinder-Mini-Neodymium-Magnet/282872710011?hash=item41dc87037b:g:bQcAAOSwIVVcd2Db&frcectupt=true
1 x self-tapping screw 4.5 x 50 mm, this is for mounting the ball bearing
8 x self-tapping screw 2.2 x 15 mm, this is for securing the cup arms and ball bearing
Important: Don't push the bearing into the top part without the 4.5 x 50 mm screw inside it, or another way of pulling the bearing out again, otherwise it can be pretty hard to get it out again, since it's a pretty tight fit.
The hall sensor shall be supplied with ground and +5 volt, and it will output a +5 TTL pulse, one pulse pr rotation, which can be connected to an Arduino or a Raspberry Pi or similar.
The anemometer can be installed on a rod or pole with a square size of 25 x 25 mm.
All the items can be printed completely without any support, as long as they are positioned as indicated on one of the pictures, where all of the items are located next to each other.
The inside of the bottom of the cups might need a little sanding, since there is very high overhang right there.
The radius to the center of the cups is 12.45 cm, which gives a circumference of 78.2256 cm, which is needed to calculate the wind speed