After waiting days for the home delivery of your precious arduino, that seem like years for a hardcore hobbyist like you guys, the last thing you want is to fry it on the first day.This post aims to point some common mistakes that eventually end up in damaging arduino.
1. Do not ever place arduino directly over metallic surface and work.
For robotics hobbysts, if you do not have any other chassis but just the metallic ones, take it easy.Just insulate the surface first and you are good to go.
2. Never short 5v to Gnd or Vin to Gnd.
For a fact , the maximum current a GPIO pin can provide or sink is 40 mA.When you short them , a current large enough to damage your PINS flows.Be extra careful ! with the Vin pin when powering up the arduino via 12 volt adapter .A 12 v supply has a greater chance of electrocuting Arduino ,as V=IR, (you know the math).So,definitely double check your circuits, before powering up.
3.Do not give more than 5v to I/O pins or analog input.
As mentioned above , the threshold current for any GPIO pin is 40mA ,the resistors inside arduino are meant to limit the current below 40 mA for a voltage less than 5V only. A voltage like 5.2 or 5.6 won’t bother however.Do not give negative voltage to analog pins.
4. Do not connect a switch or push button to any I/O pin, unless however you have set it to INPUT mode through your IDE.
When you connect the 5v to push button and then the button to I/O pin , you are trying to short the two without any significant resistance in between. So,the question arises, how is it possible to connect the two?
The magic comes from the command that follows,
pinMode( pin,INPUT) ;
When you go for this instruction, you unknowingly set up a high value resistor to that pin inside the arduino which limits the current for you, and saves the lord arduino from facing an untimely death.
5.Do not run motor directly from arduino pins.
In every DC B.O. motor ,current varies depending upon the load.When the motor is at maximum speed it takes minimum current, but as the wheels or gears are coupled to it , its speed decreases,hence current increases.Right at the start of the motor action, the shaft does not rotate(zero speed). The current is maximum at that time, far greater than 40 mA.This is another arduino-killer.