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Author Topic: Current measuring problem using ACS712 - no change in readings when plug load  (Read 933 times)
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Hi,

I am using ACS712 (sparkfun) connected to Arduino UNO. I am facing a problem measuring current, when I connect the load there is no change in the readings, and when removing load also no change.

I guess the sensor is not measuring any value, only pass current to the load.

Can any one help, this help will be appreciated.

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NL
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What readings do you get? Also, what load are you trying to detect?
As far as i can tell, you should get 2,5 volts (half Vcc) when no current detected.
According to the datasheet the reading should change ~185mV per A, so if you are drawing +1A, the reading should go to 2,685V.

Cheers,
Guido
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First, thank you for your reply.

I am trying to read 220V AC current for some devices; one of them is the mobile charger. 



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please give diagram and software
without it difficult to help.
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Left Coast, CA (USA)
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What readings do you get? Also, what load are you trying to detect?
As far as i can tell, you should get 2,5 volts (half Vcc) when no current detected.
According to the datasheet the reading should change ~185mV per A, so if you are drawing +1A, the reading should go to 2,685V.

Cheers,
Guido

But what does the value change to as the 1 amp steady current changes to both positive and negative values at a 60/50Hz rate around the +2,5 volt 'zero value'?

The output voltage will be changing constantly even when the current draw is steady. This 'measurement signal' must be processed correctly either with external signal conditioning or software functions if the intent is to obtain a accurate average or RMS current value when measuring AC power.

Lefty
« Last Edit: December 20, 2013, 11:26:16 am by retrolefty » Logged

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You don't know how much current the mobile charger is using.    If the phone is fully charged,  maybe none.

Try measuring a load with a substantial and known current like an incandescent lamp or a hair dryer.
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Thank you all for your help..

I found the problem in the gain of the sensor, clearly, it is the sensitivity of the sensor.
When I connect a load of 0.2 A the change in voltage is very small to be measured by Arduino (0.037 V), and +1A & 2A is too high to be drawn by a device.

If some one had a circuit of amplifier that can be connected to increase the voltage out from the sensor??

THANKS ALOT

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Lincoln, England
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Because you are trying to measure an alternating current, the output voltage of the sensor will swing above and below 2.5V. Unless you strike it lucky and take a measurement when the voltage is at it's highest, you are probably measuring something closer to the average current, (which for an AC signal is actually zero).

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