Is my ACS712 dead?

I've just obtained this: https://www.sparkfun.com/products/8883

Unfortunately using various code I found online nothing seemed to give me an accurate measurement. Whether or not the IP+ and IP- leads are connected, I always get a raw value of somewhere in the range of 770. If I adjust the VREF pot to max it is then somewhere in the 1000s both with a load connected and nothing connected.

Is it dead?

Before you can receive an answer, you are going to have to post a picture or diagram on how you have it hooked up. Posting the code (using code tags) would help as well.

Hi, I used the ACS712 but without the op amp. I read the signal output from the pin 7 directly with the Arduino Ax input. It will read negative +/- 5 amps. But also you can get it for 20 and 30 amps. The output normally read VCC/2 without any input. That will allow the sensor to read negative and positive current. If you read the customer reviews for your sensor you can see some are experiencing same problems as you having. There are some cheaps ACS712 sensor modules that does not use the op amp. Also you can buy one in Sparkfun that does not have the op amp. "SparkFun Hall-Effect Current Sensor Breakout - ACS712". You can do a test by reading the voltage output pin 7 and it should read VCC/2. If it does then it maybe the setting of the gain and the offset adjustment.

You have the correct capacitors (decoupling and filter)? Without decoupling anything may happen (decoupling is never optional for logic chips), without the filter cap very noisy output will be seen.

tauro0221: Hi, I used the ACS712 but without the op amp. I read the signal output from the pin 7 directly with the Arduino Ax input. It will read negative +/- 5 amps. But also you can get it for 20 and 30 amps. The output normally read VCC/2 without any input. That will allow the sensor to read negative and positive current. If you read the customer reviews for your sensor you can see some are experiencing same problems as you having. There are some cheaps ACS712 sensor modules that does not use the op amp. Also you can buy one in Sparkfun that does not have the op amp. "SparkFun Hall-Effect Current Sensor Breakout - ACS712". You can do a test by reading the voltage output pin 7 and it should read VCC/2. If it does then it maybe the setting of the gain and the offset adjustment.

Thanks. Since I'm running my arduino on 5v (with a 7.2volt battery using the onboard regulator) than I should be getting 2.5v readings with nothing connected?

Where:

RawValue = analogRead(analogIn); Voltage = (RawValue / 1024.0) * 5000; // Gets you mV

UPDATE: I soldered a wire directly to the VOUT of the ACS712 (thus eliminating the OPAMP) and I am getting correct measurements. I suspect a problem with the opamp or the trimmer pots.

Hi, Glad you found your problem. I will remove the op amp and jumper pin 7 to the output. Make sure you have the capacitor in the output pin. It is a filter cap like one of the member advised you

Measure if the wiper of trimpot R4 is set to about VCC/2 (~2.5volt). You can also measure this voltage on C2 or pin3 of the opamp. Then the opamp should be in it's working range. I think the design has a too large range of the pots, so mis-adjusting the trimmers could peg the opamp to 5volt or ground. Leo..

Hi, I think the purpose of the op+amp it is use it as buffer. I noticed that the output from the ACS712 can be loaded easily. By setting both resistors in the middle may work just right.

R4 is offset. Moves zero current through the sensor to e.g. (almost) zero volt output (or whatever). So you can use (almost) the whole range of the A/D for uni-directional current. R3 is gain. Messes with the mV/Amp output of the sensor. Leo..