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ACS711 not outputing full voltage range.
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guitchess:
Hello. 

I am trying to design a switched receptacle that is triggered by current on a parallel receptacle. 
The issue I'm having is that the ACS711 starts with a normal output (Vcc/2) but after amperage reaches about 5 amps, the output falls/rises back  to the original level.   

The IC is the x25AB version. 
Vcc is from a 1117-3.3 giving a base Vout of 1.64v.  Depending on current direction, Vout will rise to about 1.91v or fall to 1.58 before resetting.
I'm testing with a drill, which has a peak current draw rating of 7.8 amps.  The Vout resets at about 3/4 trigger pull.

If any of you more experienced designers have some advice, I would greatly appreciate the input.

Attached are schematic, pcb images, and ACS711 datasheet.
jdraughn:
When you say resetting, do you mean from 3/4 to full the current reading output resets to vcc/2, but if you release the trigger a tiny bit like back to 1/2 then the current goes back up?
mikerj:
Is that a 1uF capacitor on the output of the ACS711 (marked 105 on the schematic)? The datasheet specifies the maximum capacitive load as 1nF, a thousand times lower.
guitchess:

--- Quote from: jdraughn on October 24, 2019, 09:11:20 am ---When you say resetting, do you mean from 3/4 to full the current reading output resets to vcc/2, but if you release the trigger a tiny bit like back to 1/2 then the current goes back up?

--- End quote ---


Yes.  Once I hit that threshold, the 711s output reverts back to Vcc/2.  If I slightly release the trigger, it does go back to working.  Also, if I pulse the drill at a low level, being careful not to go past half or so, the Viout(the datasheet  label) will peak higher. 

I got to wondering if the ACS711 was being upset by the magnetic flux(I'm a rookie, not sure what this is really called) of the relay, but yesterday I  tested without the jumper that leads to the MCU and it functioned no differently. 

I was also thought that the current draw of  the relay may be keeping the 711 from functioning properly, but the no jumper tests made no difference.
guitchess:

--- Quote from: mikerj on October 24, 2019, 11:46:52 am ---Is that a 1uF capacitor on the output of the ACS711 (marked 105 on the schematic)? The datasheet specifies the maximum capacitive load as 1nF, a thousand times lower.

--- End quote ---

Yes, I had made that mistake.  Unfortunately, changing it to the proper value made no difference in the IC's output. 

I had also used a 10k instead of the 1k resistor for the fault pullup.  Sadly, the change to 1k failed to make the IC function as expected.
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