This is an incomplete version of the power supply used for the Alertness Monitor with hourly LED Display. This circuit used a Dual Color LED. Green meant Alert and Red meant No Alert or acknowledge press.
Power Electronic Circuits - Basic Power Supply Designs
I can write here only in "Electronic English". Focus on the tech not grimmer. It may be like Pascal with a touch of Acronyms, codes and circuit axioms.
The top part is a 5V regulator with 0.7 Diode boost, means 5.7 V DC. The battery was floating on this point above the zener Z4, that connection comes from outside. A protection fuse maybe needed in case Zener draws more current. The Zeners were test selected to get above 6V along with the diode.
Read more »