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Topic: ACS712 - 30A vs 5A.... (Read 624 times) previous topic - next topic

dannyboyfl

Can I use a ACS712-30A to read currents from devices that are bellow 1A? I have a 30A version. But I know that what I'm trying to measure around 150mA, and I'm not getting any fluctuation in the read. 

Thanks, Dan!

Code: [Select]

int curRead;
void setup() {
  Serial.begin(9600);
}

void loop() {
  curRead = analogRead(A0);
   delay(1);
  Serial.println(curRead); 
}

Chagrin

The ACS712-30A outputs 66mv/A. 66mv * .150A = 9.9mv.

The Arduino, by default, measures 1024 points from 0 to 5V, or (5/1024 =) 4.8mv per step. You will see very little change in your analog reading.

Also, the ACS712 reports 7mv peak to peak noise. More or less you just won't be able to read such low currents with this sensor.

dannyboyfl

Chagrin, Thanks for the response!
What would be a good sensor to use? Would you have any suggestions?

I was thinking of getting one of these. It looks like it would have other uses in the longterm.
INA219 High Side DC Current Sensor Breakout - 26V ±3.2A Max
http://www.adafruit.com/products/904

Chagrin

The Adafruit board looks like a good choice.

Not much more that I can add that isn't already stated in Adafruit's description of the board.

enjoynering


The ACS712-30A outputs 66mv/A. 66mv * .150A = 9.9mv.

The Arduino, by default, measures 1024 points from 0 to 5V, or (5/1024 =) 4.8mv per step. You will see very little change in your analog reading.

Also, the ACS712 reports 7mv peak to peak noise. More or less you just won't be able to read such low currents with this sensor.

I'm going to get a ACS712 for arduino and I don't know which I should choose.

The ACS712-30A outputs 66mv/A. 66mv * .150A = 9.9mv.
The ACS712-5A outputs 185mv/A. 185mv * .150A = 27,75mv.

If the arduino measures 4,8mv per step:
The ACS712-30A --> (9.9mv)/(4.88mv per step) = 2.02 step
The ACS712-5A --> (27.75mv)/(4.88mv per step) = 5,68 step

It's better the ACS712-5A?

Thanks!

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