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low-voltage alarm

When a car gets left with a door not closed fully, the door light stays on and drains the battery so the engine won’t start. This project monitors the voltage of a 12 V battery and sounds an alarm if the voltage drops below a configured threshold.

It also has logic-level RS232 ( the 4-pin connector on the right in the photo above) via which it reports the voltage as currently measured.

The schematic was prepared with gschem:

Then pcb ( also part of gEDA) was used to design a veroboard:


The archive includes full source code, along with gEDA source files for the schematic and a single-sided PCB layout.