[MakinStuff] wrote in to let us know about a project he did for new and improved interfacing to the ubiquitous cheap Chinese digital calipers. Interfacing to this common caliper model is well-trod ground, but his project puts everything about interfacing and reading the data in one place along with some improvements: a 3D printed connector that makes mating to the pads much more stable and reliable, a simple interface circuit for translating the logic levels, and an interrupt-driven sample Arduino sketch to read the data. Making the sketch interrupt-driven means the Arduino never sits and waits for input from the calipers, making it easier have the Arduino do other meaningful work at the same time, ultimately making it easier to incorporate into other projects.
The connector has spaces to insert bare wires to use as contacts for the exposed pads inside the calipers. Add a little hot glue and heat shrink, and you’ll never have to fiddle with a hacked-together connection again.
This common caliper model has been hacked and re-purposed in interesting ways. We’ve seen them used as a Digital Read Out (DRO) on a lathe as well as being given the ability to wirelessly log their data over Bluetooth.