80mm Field Mill

thingiverse

This is an 80mm IoT field mill that's usually situated outside, a few feet above the ground and pointing towards the ground where it measures the local E-field strength and polarity. The field mill has a space for a NodeMCU module that sends out the E-field measurements wirelessly. Post-Printing To complete the field mill, you'll need some non-3D parts like 3mm heat set inserts, 3mm screws, 4-40x1/4" set screws, 4-40 jam nut, 5mm shaft, 5x16x5 bearing, motor, flex tubing, copper foil tape, custom circuit board, NodeMCU module, and a printed label for the optical encoder. The rotor is covered with self-adhesive copper foil tape. A 4-40 x 1/4" set screw with a 4-40 jam nut on top holds the rotor in place and electrically connects the foil to the shaft. The 5mm shaft must be grounded; I used a repurposed motor brush as a contactor to the shaft. The faceplate and frame are bonded together to form one piece, using ABS for these parts and solvent bonding them together. More copper foil tape goes on the faceplate sensor areas and is soldered to wires fed through the faceplate. The encoder wheel needs to be drilled out to 5mm for the shaft, and all set screw holes tapped for 4-40 threads. A shaft adapter is used to bring the motor shaft up to about 5mm, then a bit of flexible tubing is used as a shaft coupler.