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ACS712 to detect ZERO amps

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igeorge

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Hello,
I would like to ask some help in using Allegro's ACS712.
According with data sheet , will sense the AC current, BUT, the voltage goes from .5V at -20A to 0V at no current flowing at all ( or zero crossing), then goes up to 4.5 A for +20 A
In my application, i have a heater which i try to put an alarm if the resistance is burned out and is no current flowing through the chip 712
I do not know how to implement this.
All i need is like a digital output converter
If current is bigger than 0.5 , in either direction ( I am using 120VAC) to get an output to an optocoupler. or what ever .
I can drive a transistor or something else and get the alarm.
When the heater is burned out , and is no current flowing , even if the ACS712 give me 2.5 volts, i need to get a ZERO, or in other words, turn the transistor off, or alarm ON.
Please help as i do not have a clue how to integrate or use chips to achieve that..
My biggest problem is that 2.5 volts present when is no current flowing.
Thank you
Ion
 

tpetar

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You should read datasheet for ACS712-20 0A is at 2,5V and 20A is at 4,5V and 0,5V is -20A.

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