Arduino button interrupt triggered on high power switch on
<p>I have a nearly finished prototype using an arduino uno. Basically its purpose is to switch a 2000w main AC heating load using a heavy relay on and off. The input of the relay is comming from the mains but is connected to the power company using a special meter that is only switched on between 23-07 hrs at night. The power for the arduino is continous by the way, so this stays on.</p>

<p>The whole thing is nicely build into a box with on the front an small lcd display and a button, connected using 20cm wires to the arduino board (I am using a protoshield).</p>

<p>The button is pulled up with a 10k resistor which is pulled to ground when pressed. I have put a 0.47 uF cap on the input pin = pin 2 to also debounce the circuit a bit. In software I am using an interupt on the falling edge to detect button presses. The whole thing works nicely... Except...:</p>

<p>When the load ac input is switched on by the power company this is sometimes recognized as a button press! I am thinking that the suddon power spike induces a voltage in the 20 cm button wires which is recognized as a falling edge. How can I avoid this?</p>

<p>I am equiped with multimeter, oscilloscope, soldering... so I can try out any suggestions in detail.</p>