pivot

5 Articles

Screwless Eyeballs Are A Lesson In Design-For-Assembly

June 8, 2024 by 9 Comments

[Will Cogley] makes eyeballs; hey, everyone needs a hobby, and we don’t judge. Like all his animatronics, his eyeballs are wondrous mechanisms, but they do tend toward being a bit complex, especially in terms of the fasteners needed to assemble them.

But not anymore. [Will] redid his eyeball design to be as easy to assemble as possible, and the results are both impressive and instructive. His original design mimics real eyeballs quite well, but takes six servos and a large handful of screws and nuts, which serve both to attach the servos to the frame and act as pivots for the many, many linkages needed. The new design has snap-fit pivots similar to Lego Technic axles printed right into the linkage elements, as well as snap connectors to hold the servos down. This eliminates the need for 45 screws and cuts assembly time from 30 minutes to about six, with no tools required. And although [Will] doesn’t mention it, it must save a bunch of weight, too.

Everything comes at a cost, of course, and such huge gains in assembly ease are no exception. [Will] details this in the video below, including printing the parts in the right orientation to handle the forces exerted both during assembly and in use. And while it’s hard to beat a five-fold reduction in assembly time, he might be able to reduce that even more with a few print-in-place pivots.

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Water Level Sensor Does Not Use Water Level Sensor

August 31, 2022 by 26 Comments

When interfacing with the real world, there are all kinds of sensors available which will readily communicate with your microcontroller of choice. Moisture, pH, humidity, temperature, location, light, and essentially every other physical phenomenon are readily measured with a matching sensor. But if you don’t have the exact sensor you need, it’s sometimes possible to use one sensor as a proxy for another.

[Brian Wyld] needed a way to monitor the level of a remote body of water but couldn’t use a pressure or surface-level sensor, so he used a sensor typically intended for geolocation instead. This particular unit, an STM-type device with a built-in accelerometer, is attached to a rotating arm with a float at one end. As the arm pivots, the microcontroller reports its position and some software converts the change in position to a water level. It’s also paired with a LoRa radio, allowing it to operate off-grid.

Whether there is a design requirement to use an esoteric sensor to measure something more common, or a personal hardware limitation brought about by a shallow parts drawer, there’s often a workaround like this one that can accomplish the job. Whatever the situation, we do appreciate hacking sensors into other types of sensors just as much as anything else.

Three-Conductor Pivot For E-Textiles Is Better Than Wires

February 13, 2019 by 1 Comment

Pivots for e-textiles can seem like a trivial problem. After all, wires and fabrics bend and flex just fine. However, things that are worn on a body can have trickier needs. Snap connectors are the usual way to get both an electrical connection and a pivot point, but they provide only a single conductor. When [KOBAKANT] had a need for a pivoting connection with three electrical conductors, they came up with a design that did exactly that by using a flexible circuit board integrated to a single button snap.

This interesting design is part of a solution to a specific requirement, which is to accurately measure hand movements. The photo shows two strips connected together, which pivot as one. The metal disk near the center is a magnet, and underneath it is a Hall effect sensor. When the wrist bends, the magnet is moved nearer or further from the sensor and the unit flexes and pivots smoothly in response. The brief videos embedded below make it clear how the whole thing works.

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Center Pivot Pen Plotter

September 18, 2012 by 22 Comments

This center pivot pen plotter is an interesting take on the idea, and manages to somewhat simplify the fabrication when compared to a gantry-style built.

Normally we’d see a gantry that travels on two rails, with a print head that moves along its length. Here the gantry is anchored on just one side, with a chain driven system to rotate it along the plotting surface. The print head uses a fine-point felt-tipped marker. It still travels along the arm as you would expect, and can be tilted away from the paper for repositioning.

What was made easier in hardware ends up adding to software complexity. The benefit of a traditional system is that it uses X and Y coordinates to plot a design. The pivot of this mechanism means that as the print head moves further from the center of the machine, the distance between each pixel is magnified. But the clip after the break proves that this issue has been solved.

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