From left to right: most significant digits and ATtiny4313, least significant digits and ATtiny4313, CD4060 oscillator and divider. Decoupling capacitors on the Vcc supply rail (that must be used in digital logic circuits!) prevent detection of false 1 Hz input pulses.
The circuit in the picture is powered with a 18650 LiPo cell at about 3.8V and it has been running all night to test the firmware past 10 hours of operation.
At powerup is starts counting immediately. First only seconds are shown. Then minutes and seconds until 59' 59". Then it switches to what is shown in the picture. After 9h 59' you get HH MM.
The font was chosen as a trade off of readability vs cozyness vs current consumption. There is some MSD blanking too, but it doesn't last long.
Further improvements before looking for a suitable box: add the battery, a 1S LiPo (dis)charge controller, a power switch. Maybe some firmware improvement once the timer is shown to the public.
Besides as kitchen timer, it can be used as elapsed work(-day) timer ... that's where I will hopefully gather some extra feedback.
The firmware is written in BASCOM. I want to do some further optimisation before uploading the code to my github account. Binary is available on request as well as TIL305, if need too.
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