user8500: I have a ACS712 module that I am connecting to my Arduino Uno to read the current spike when my door bells rings (and then trigger some events in my "sketch").
In my country doorbells use the ~115 VAC at ~60Hz. So, I just opened the doorbell and connected the ACS712 module in series. 
I do not know how much amperage my doorbell draws, but it is hardly the 30A supposedly supported by the module. 
At this point I am not connecting the OUT pin to the Arduino, only VCC and GND to the +5V and GND of the Arduino Uno. (I am also tried connecting the OUT pin to A2 in the Arduino).
What happens is that as soon as I ring the doorbell the Arduino hangs up. Sometimes I even have to physically unplug the Arduino to get it back to life.
It doesn't necessarily happens in the first bell, but it does not survive 3 rings in a row. 
The ACS712 chip is supposed to provide 2.1 kVRMS of isolation... it doesn't seem likely that the "kickback" from the bell would be 2100 VAC... so I cannot imagine how/why my Arduino is hanging up, when it is supposed to be completely isolated from the AC (that's the whole point of the Hall Effect current sensor).
I added some capacitors to the VCC/GND pins with no luck. 
So... any ideas on 1) how to protect the Arduino from hanging up?, 2) what is making the Arduino hang up?.

user42474: There are two probable solutions to your problem:

The ACS712 is a hall effect based sensor and also door bells have a solenoid attracting a hammer to hit the bell. Try and place the sensor away from the bell, this could avoid any possible magnetic interference. (This is less likely to happen but there is a fair amount of chance)
May be, there is a problem with the code OR the laptops USB. Connect the Arduino to the sensor and the OUT pin to an analog input. Run the following code:

  void setup()
  {
     Serial.begin(9600);
  }
  void loop()
  {
     Serial.println(analogRead(A2));
  }

If this doesn't work, probably there's a problem with the sensor or the connections.
Give me more details about your connections, code and post a picture of your project for more help.

8500: <p>I have a <a href="http://www.banggood.com/1PC-30A-New-Range-Current-Sensor-Module-for-ACS712-p-86583.html" rel="nofollow">ACS712 module</a> that I am connecting to my Arduino Uno to read the current spike when my door bells rings (and then trigger some events in my "sketch").</p>

<p>In my country doorbells use the ~115 VAC at ~60Hz. So, I just opened the doorbell and connected the ACS712 module in series. </p>

<p>I do not know how much amperage my doorbell draws, but it is hardly the 30A supposedly supported by the module. </p>

<p>At this point I am <em>not</em> connecting the OUT pin to the Arduino, only VCC and GND to the +5V and GND of the Arduino Uno. (I am also tried connecting the OUT pin to A2 in the Arduino).</p>

<p>What happens is that as soon as I ring the doorbell the Arduino hangs up. Sometimes I even have to physically unplug the Arduino to get it back to life.</p>

<p>It doesn't necessarily happens in the first bell, but it does not survive 3 rings in a row. </p>

<p>The <a href="https://www.sparkfun.com/datasheets/BreakoutBoards/0712.pdf" rel="nofollow">ACS712 chip</a> is supposed to provide 2.1 kVRMS of isolation... it doesn't seem likely that the "kickback" from the bell would be 2100 VAC... so I cannot imagine how/why my Arduino is hanging up, when it is supposed to be completely isolated from the AC (that's the whole point of the Hall Effect current sensor).</p>

<p>I added some capacitors to the VCC/GND pins with no luck. </p>

<p>So... any ideas on 1) how to protect the Arduino from hanging up?, 2) what is making the Arduino hang up?.</p>
 42474: <p>There are two probable solutions to your problem:</p>

<ol>
<li><p>The ACS712 is a hall effect based sensor and also door bells have a solenoid attracting a hammer to hit the bell. Try and place the sensor away from the bell, this could avoid any possible magnetic interference. (This is less likely to happen but there is a fair amount of chance)</p></li>
<li><p>May be, there is a problem with the code OR the laptops USB. Connect the Arduino to the sensor and the OUT pin to an analog input. Run the following code:</p></li>
</ol>

<pre class="lang-js prettyprint-override"><code>  void setup()
  {
     Serial.begin(9600);
  }
  void loop()
  {
     Serial.println(analogRead(A2));
  }
</code></pre>

<p>If this doesn't work, probably there's a problem with the sensor or the connections.</p>

<p>Give me more details about your connections, code and post a picture of your project for more help.</p>
