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Measure DC current of a motor using an Arduino nano

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abouabdelmajid

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i am trying to mesure the curent of a 12v DC motor using an arduino nano. i used this diagram

schéma.png

i used this code

Code C - [expand]
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void setup() {
Serial.begin(9600);
}
void loop() {
float average = 0;
for(int i = 0; i < 1000; i++) {
average = average + (.044 * analogRead(A0) -3.78) / 1000;
//5A mode, if 20A or 30A mode, need to modify this formula to
//(.19 * analogRead(A0) -25) for 20A mode and
//(.044 * analogRead(A0) -3.78) for 30A mode
delay(1);
}
Serial.println(average);
}


instead of having the right value 12.92ma (measured by amperemeter) i am havung wrong negative values

Somebody can help me please
 
Last edited by a moderator:

Hi,

Sadly, I think we can't help.
* We don't know the measurement range of your system (to calculate the multiplier. In your case: 0.044A/LSB)
* and we don't know the zero_current_offset of your system. (to calculate the subtractor. In your case: 3.78A)

Klaus
 

Hello,



Datasheet of your sensor ?

if it is an ACS712 , offset is arround VCC/2
and with a scale of 30Amps, no chance to measure 12.92 mAmps !

Event with a scale of 5Amps..
This kind of sensor dose'nt cover all the scale
ie: for 5 Amps scale AC712 sensor
you have 185mV/Amps so with ADC10 bits 5V => 37.88 points / amps
so +-512 poinst => +-13.5 Amps for +-2,5V,
it is not fo +-2,5Amps!
 

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