“This project Instructable is a build of a multi function Timer.
This timer is capable of functioning as:
A general purpose alarm with selectable times between 1 second and +90 hours. Having a count down with audible alarm and/or control of external device till finished then a count-up indication of time since alarm. A nap timer with 7 selectable times, count-down and alarm on completion. A meditation timer with 4 selectable times, with count-down and a short chirp on completion, count-up with another chirp at 5 minutes after that . This project may ether be built as described here or modified to suit. I previously built a timer with this functionality and used it in my first Instructable to control the UV exposure box.
I thought I could just publish the original program and board designs. However, for some reason I could not find the code. I also wanted to make improvements to the hardware to make the control circuits more flexible and reduce battery drain. The resulting redesign of the main circuit board and re-write of the code provides an opportunity to discuss the programming and hardware design approach.
Whenever I create a circuit board I often find that there are flaws in the design or placement of components, The boards I build are also one of two offs. Plus, I just like to be involved in a all aspects of a project from start to finish. These are some of the reasons I make my own circuit boards rather than send the Gerber files overseas for manufacture. Maybe I’m just old and stuck in my ways. This project reflects this bias. Since I make my own circuit boards, my designs and my Gerber files do not meet manufacturing standards, I have not included these files. Those who do not wish to etch and finish the boards are welcome to prepare their own designs and post the Gerber files in the comments section. Please have your boards manufactured and tested before posting.”