Inspired by microwave ovens and similar, I decided to create a KISS(!) simple to use kitchen timer.
It supports two modes of operation:
1. fixed intervals where you can choose from the most commonly used timing intervals
2. free-form where you on a logarithmic kind of scale can choose timing freely
I've done two versions, the original based on an PIC 16C84 and a 3-key "keypad". The latest as described based on a 16F628 sports a single button and a rotary encoder.
User interface is based on "silent accept" - if you do not make a choice within 5 seconds you have chosen.
That is, when the device is turned on, if you do not make a selection, it turns itself off again.
When using the dial to choose a timing period, after 5 seconds of inactivity the last timing is selected (and 5 seconds deducted of course).
When the timer is active, it gives a silent beep every minute. And in the last minute it gives a silent beep every second.