ACS758LCB-100U AC current.

[georpo]

The yellow trace above is the output of the ACS.
The circuit already has ZC detection to sync with the phases and fire the triacs.
In your example, if I wait 5mS after zero crossing and then take a reading I will probably read '0' if triggering is done beyond 90 degrees which is 5mS.
I do not understand how this could work.
_________________
George.

[Woody]

It was a while ago, and it was a bit of a 'let's see if I can do it this way' project, but from the top of my head:

- When the ACS712 is in an AC powerline shunting current it gives off a voltage between 0 and 5V, a 50Hz sine around the 2.5V mark. 2.5V is 0A.

- Period @ 50Hz is 20 msec. I made a 0-crossing detector, connected to an external interrupt. When that fired it started a 5ms timer.

- When the timer rolled over an interrupt was generated that started an AD conversion. This conversion was then more or less done at a top of the sine.

- At zero cross you don't know if you hit a 'mountain' or a 'valley' in the sine, but that can easily be established by testing the ADC value: bigger than 2.5V = mountain, less that 2.5V = valley. In the first instance you subtract 2.5V from the AD value and then have a ratiometric value for the current that was flowing. In the second instance you subtract the AD value from 2.5V and also get that value.

I remember noise was a bit of a problem, the relay next to the ACS was a stupid mistake, but on the whole it did what I wanted: to know if there was AC and to see if current actually flowed and if that flow increased or decreased when somewhere else something got connected / adjusted.


(edited for language)

[temtronic]

re: