ACS709 Hall Effect sensor


I've been struggling with this for days on end, and searched for solutions until I found a sort of solution with the emon1 library...perhaps I should start from the beginning...I'm trying to use an ACS709 hall effect sensor in conjunction with an Arduino to measure AC current. My problem is that most (if not all) examples on the net is for DC current, and it does not work - it gives out a constant current reading...even with no current connected.

Then I found the OpenEnergyMonitor library, and it at least gives me some reading. But here I have a problem of selecting the correct calibration value. I have used the current_only example code, and the measurements looks more acceptible but not quite correct (0 current still gives a value).

Is there someone who has experience with the Arduino and the ACS709 in measuring AC current?

Any help will be appreciated.



MartinR's picture

Re: ACS709 Hall Effect sensor

I haven't looked at the ACS709 but I've played with other devices from the same family. They are very easy to use as the output is already referenced to Vcc/2 so they can be directly connected to an Arduino analogue input.

The ICAL value in EmonLib represents the number of amps per volt, as seen at the analogue input. So if, for example, the spec sheet for your device says 56mV/A then ICAL=1/0.056=17.86.

If you are seeing a small current with zero input then it's probably noise but if there's a significant current then something else must be wrong.

krugerrc's picture

Re: ACS709 Hall Effect sensor

Thank you very much for your reply...I will go make the changes and report back...

krugerrc's picture

Re: ACS709 Hall Effect sensor

OK...tried it and found it to be working quite nicely. It does prove to have some noise, though...about 80mA. Is there a way to minimize this noise in hardware? I know in software I can merely subtract it...

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