Housing for homemade desktop thermometer and hygrometer

thingiverse

I've had this homemade electronics device at home for years, constantly intending to craft a housing for it when I have some spare time. The commercial empty housing is already on hand, but I never managed to motivate myself to drill, dremel and file the rectangular LCD window into it. Thankfully, I waited until the world and I discovered 3D printing. This housing was built from scratch with FreeCad, one part using the "part" workbench and the other part designed using the "part design" workbench. The two pieces fit together perfectly, with guides on the upper and lower edge ensuring a tight seal. Using only two screws in each corner instead of one revealed some very small gaps at the top and bottom edges of the long sides, but for practical purposes I'm fairly satisfied with the results. All you need to complete this project are two M3x14 screws. The domes on the front side were designed so that M3 screws could be self-cut into the plastic. This worked well for me using PETG material, although I suspect PLA might break if you try to force the screws in. For those interested in electronics: I created this design as a challenge to see how much software functionality could fit into 1024 bytes of Flash memory on the ATtiny13. I wrote the LCD driver for an old Ericsson SH888 mobile phone display, the driver for the thermometer/hygrometer sensor and a clever combination of hardware and software to generate the negative LCD contrast voltage. The internal LCD was also used to read the battery voltage, convert all data into decimal readings and display them on the LCD. Furthermore, I wrote highly optimized power-saving software that allows this device to run for many months on three rechargeable AAA batteries, despite the fact that the ATtiny13 is far from the most power-efficient processor available. All of this fit into 1024 bytes, but there wasn't much memory left over in the end.