[MakingDevices] has developed a straightforward stopwatch that would make for a great introduction to area mount electronic style and assembly. The venture is open up resource components (OSHW) licensed, with Gerbers, KiCAD data files, and software all accessible.
Conceptually the stopwatch is straight ahead, with a row of two 4 digit seven-phase shows currently being pushed by a PIC18LF14k50 microcontroller through several NPN transistors. The PIC doesn’t quite have adequate knowledge lines to travel the two displays at the moment so an inverter is made use of to toggle in between the two seven-phase blocks.
The circuit is continually powered from a CR2032 coin mobile battery. For normal usage with display, [MakingDevices] estimates 30+ hrs of operation and 140+ several hours with out show, but nonetheless counting time. When idle, the “Extreme Minimal-Electricity (XLP)” capabilities of the PIC place the working window estimates well over and above the self discharge of the coin cell battery. There’s an in circuit serial programming (ICSP) footprint that accepts a pogo pin TC2030-MCP-NL adapter for flashing the PIC.
Don’t allow the simplicity fool you, this is a very well documented task with in-depth posts about the design, simulation and battery consumption. Many movies and glamour photographs give a entire image of the approach, from layout, assembly, testing to closing validation.
It’d be excellent to see the undertaking prolonged or hacked on even more, possibly with a lovable enclosure or case.