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
, which supports high-voltage programming. Since HV programming is not required,
so that static will not damage the AVR
MISOare used instead of the traditional
RXDbecause they’re not so ambiguous.
TXDrefers to the DTE transmitting, not the DCE.
MOSImeans “Master Out, Slave In”
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.