Digital calipers have been an important tool in machine shops and hackerspaces for a long time now. Being able to quickly get an accurate length measurement can greatly speed up design and prototyping. While many low-end calipers output their measurement over a serial port, MuTko wanted to make a truly hackable pair of calipers from the ground up.
Of course, the digital variety descended from the much older dial or scale calipers. These gave just as much accuracy, but reading scale calipers in particular took a few seconds longer, and when taking many measurements this could add up quickly. Digital calipers come in a wide range of accuracy and price points and are all based on the same concept: a row of PCB traces on the stationary caliper emit a signal that measures the movement and direction of the opposite caliper using capacitive coupling.
The applications are quite interesting; motion control by attaching the PCBs to a moving part to get very precise, small steps; very high-speed data output for use with robotics or pass/fail testing; and of course, just having a fully custom, hackable measurement tool for your lab. You can do a lot more than just output the data over serial. You could show the raw values on the display, or set particular lengths and have it beep faster as you get closer to the set value. The possibilities are up to your imagination!
At this point, the project isn’t quite ready as a tool: there are a few boards available for tinkering and to help test out the code. You need to add a XIAO and also mount the boards into a housing — I suspect you could hack them into a pair of cheap calipers from your local hardware store or online. As soon as all the kinks are worked out, hopefully a fully assembled version will be available, and we will definitely cover it here when it comes along!
source https://blog.tindie.com/2024/11/digital-calipers-from-scratch/
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