Current Measurement for Car Alternator

The project uses the alternator to measure the current in order to detect failures or helps in the proper alternator selection through the use of Hall Effect Sensor.

The Hall Effect current sensor from Allegro Microsystems is being used to record transients and faithfully reproduce both AC and DC currents as the sensor contains a maximum current rating of 150A and outputs a linear 0-5V signal proportional to the current that passes through the device. The ADC functions are performed by the Atmel ATmega8 microcontroller as it receives the output of the sensor. The data is sent out to a MAX232 level converter through the UART of the microcontroller. Using the HyperTerminal program, the data stream can also be obtained. The raw data can be manipulated by using Excel and be made into graphs.

When the truck was being driven a clear 20A drop can be seen from the plots to show how much power is being consumed by the transmission when it is in gear. The target supply voltage in this application is 11-14V although the supply voltage can be extended to 45V with the appropriate version of the 7805 voltage regulator.

Rest of the project