ACS 712 current sensor

[jonwhite]

Hello I'd like to use this sensor and make a simple switch I'd like to measure the current t of a single phase and when it gets to say 200 ma output 5v wonder if anybody could point me in the right direction ie what if I component I could use that would do the job
Many thanks

[Seekonk]

Single phase? Do you want to look at one side? Do you want average or peak?  The output centers around 2.5V.  A three terminal LM431 trips at 2.5V.  Add a pot and you could easily look at one side of the waveform and look at the peak.  A PNP transistor could then invert the signal.  Or use a comparator, the 431 could be your reference.

[jonwhite]

I want to measure an AC signel  single phase and when that phase is lost trigger a 5v output

[Seekonk]

Why 5V? Is this a micro? Does it have an A/D?  Do I have to do all the work?

[moffy]

The application circuits in the data sheet are quite suitable, if slightly modified. You just need a comparator after the rectified and filtered output to convert your signal from analogue to digital.

[Seekonk]

The output from a 712 in an ac application will be a low level ac signal. That could be amplified and rectified.  Something as simple as running it directly into a logic input may be sufficient for go/no go application.

I just got back to project that uses a 5A ACS712.  At 200ma DC I only get 10 counts on a 10 bit A/D.  Of that 4 counts are noise.   And I've found these are drifty with temp.  Maybe because these are cheap ebay clones.  I think YOU would have difficulty using these in this application.  You would be better off using a current transformer with multiple loops.