Lehman Seismometer Parts

thingiverse

A Lehman Seismometer is probably the most common DIY seismometer design around. The basic principle is straightforward: a freely swinging arm with a mass at the end will move when there is ground motion from an earthquake, converting that motion into current through a pickup coil. This current can be easily read by a computer or microcontroller like an Arduino. This design works well to pick up horizontal (side-to-side) ground motion from an earthquake. To pick up vertical (up-and-down) motion, you can modify this model, but it's recommended that you use the TC-1 Slinky Seismometer design instead. These seismometers are ideal for picking up distant quakes and work best with 20mm 80/20 t-slot aluminum bars and half inch aluminum rods. The pickup coil and magnet holders use #6 screws, while the damper plate is a 2-inch square copper plate. The magnets are 2-inch by 1-inch by 1/4-inch rectangular bar magnets, held in place on a 3-inch metal square that fits into the model. The weight at the end of the arm consists of multiple 1/4-inch bolts. To build this seismometer, you'll need to print several parts, including the Weight Disk, Plate Stand, Magnet Plate Set Screw, Lehman Wire Spool, and Tuner Key Holder. Post-printing steps include assembling additional parts and attaching hardware to connect all the pieces together. The frame is made of 20mm 80/20 bars, with a 4-foot bar for the length, a 2-foot bar for the standing piece, and a 1-foot bar for the stabilizing cross piece. A 3-foot long aluminum rod serves as the swing arm, supported by a guitar string or any other strong material. The pickup coil requires a large amount of fine-coated wire, such as 40-gauge wire, which is carefully wrapped around a screw to create a functional coil. The damper plate is a 2-inch by 1/8th inch copper square plate that helps stabilize the swing arm. To assemble the seismometer, you'll need to attach the magnets to their holders and adjust the support cable to center the magnets over the pickup coil and damper.