This project was created to address an issue with the layout of my house. The door from the garage into the house overlaps with another door. If this door is left open it could get hit by the overlapping door. To prevent this from happening a visual indicator was installed to show if the overlapping door is left open.
VCC is supplied by four AA batteries. The circuit is broken down into two parts. On the left is a circuit that shows if the door is open. On the right is a low battery indicator. LED2 is a flashing led. This part was selected to lower current draw versus an always on led. U1 is an open collector voltage sensing chip that triggers at 3.6V.
Gerbers and BOM for the PCB can be found at:
Photos of completed and installed circuit: