The picture below shows the system layout of Fuelino "proto1".
In its most simple configuration, Fuelino requires only 4 pins connections:
- Battery voltage (12V). Positive pole of the injector.
- Ground (0V). Vehicle chassis metallic frame.
- Injector command from original ECU. The original ECU has a transistor which controls the status of this pin: when the transistor switch closes, the voltage becomes 0V, and the current starts flowing in the injector (if it is connected to this pin, as it is on the original vehicle); when the transistor switch opens, this voltage becomes the same as battery voltage, and the current start to decrease until stopping. Before Fuelino installation, this pin is connected to the negative pole of the injector, since the original ECU directly commands the injector; after the installation, this pin will be connected to Fuelino, but the original ECU will think that it is directly controlling the injector.
- Injector command output from Fuelino. Also this pin is the negative pole of the physical injector. Fuelino will control the status of this pin using a transistor switch, as the original ECU does in the original configuration. After Fuelino installation, the injector negative pin will be connected to Arduino, and not anymore to the original ECU.
Additional pin connections (optional) are necessary to acquire the analog signal coming from the throttle position sensor (TPS) or for SD card logging (6-poles connector on Arduino).
The connection of the cables to the Fuelino is done using screw terminals, as visible in the picture below. The pin which is not described in the picture outputs a 9V regulated voltage).