An Arduino can be used to test the life of any battery with less than 5 volts, Boxall says. So, for a quick way to see how much juice your AAA, AA, C, or D batteries have left, build this Arduino ...

Just make sure you modify the code for the correct number of cylinders in your vehicle. Simple, cheap, effective – even if it is more of a shift point indicator than true tachometer, it gets the ...

Open the Arduino software and paste the Arduino code (the text in the box near the bottom of the post) into a new sketch. Click Sketch > Verify / Compile to make sure the code is properly in there.