A countdown timer with super bright 7-segment displays that flash when the time is up, instead (or in addition to) an audible alarm.
The design is based on a PIC16F886 microcontroller which drives the displays using a TLC5916 LED driver and dual P-channel MOSFETs. A rotary encoder with a push button is used for input, in addition to two microswitches, one for power and one for toggling sound. The sound switch also toggles a green 0603 indicator LED.
The device is powered from two AAA batteries, which will hopefully deliver adequate battery life.
For more detail: ytimer
EasyEDA: Ideas for Circuit Design, Innovation for Electronics Access
Free Circuit Design: Schematic – Simulation – PCB Layout – Gerber Viewer
JLCPCB Prototype: Only $2 for 10pcs 10×10cm, 24 hours Quick Turn, DHL Delivery in 3 days