Have you ever wondered how much electric current your truck/car uses? It is always interesting to know things that isn’t displayed in front panel. Measuring alternator current can also have practical means – it allows detecting failures, or simply helps in right alternator selection as high output alternator isn’t always a best choice. Josh used a hall-effect current sensor from Allegro Microsystems which is capable of measuring currents up to 150A and outputs pretty linear 0-5V signal which can be directly fed to microcontroller.

He came up with pretty simple circuit where AVR Atmega8 microcontroller reads sensor data via ADC input and sends data through RS232 interface to PC where data can be analysed in convenient way.

I wouldn’t mind to add a simple display near the dash-board. From my practical perspective – it wouldn’t hurt to add another sensor for car batteries. It may be actual for older vehicles with diesel engines. I noticed that before engine start the lamp, indicating “Glow Plugs on”, turns off before the pugs actually goes off, and starting engine too early really hurts alternator as plugs require lots of current.