Josh from imsolidstate built this circuit to answer the age old question,
how much electric current does a truck really use? Actually, he was having trouble with the alternator (electricity generator) on his vehicle, and wasn’t sure if he should replace it with a regular one or a high output version, to help power his horse trailer. To figure out what to use, he built this current measuring circuit, which uses a hall effect sensor to measure the current coming from his alternator. After installing it in his vehicle, he used the system to measure how much current was drawn in a variety of situations. Since the trailer didn’t appear to draw much power, I can assume he went with a standard alternator. Schematics and source code are available on his website.
I’m guessing that most people don’t have a huge need to monitor their alternator like this, however the circuit can be used anywhere you need to measure current. I could see it coming in handy when designing a battery-powered robot or benchtop cnc machine. [via embedds]
8 thoughts on “Measuring alternator current with a Hall Effect Sensor”
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These are in all apple laptops, sometimes as a secondary board, and I believe they are used to measure battery voltage.
Apple uses hall effect sensors to detect when the lid is closed.
Why use an exotic hall effect device? The differential ADC input on some AVRs has a resolution as tiny as 120uV. They already went to the trouble of making a custom PCB, so a careful layout could avoid the noise issues. The resistance of a regular auto battery earth cable is probably a few 100 microohms, so using a similar length of heavy cable as the shunt, the AVR should easily be able to resolve to the nearest amp with no extra analog hardware or probably better by averaging several samples.
Sure, a shunt resistance measurement would probably as well, and would have a lower part count.
However, the hall effect sensor isn’t too expensive, is probably easier to get working, and provides a bit of extra isolation between the microcontroller and the circuit that is being measured. Why not use it, especially if you have it on hand?