bob112112:
I was wondering if i can supply 12 volts from my power supply ( wall socket ) to arduino ( Vin) .My Arduino mega uses about 40 pins, and currently 5volts is enough to power up my arduino .
If so do i just connect +ve to Vin and Gnd to ...?
If it's a regulated supply, then yes.
What does that mean. Have you connected stuff to 40 pins?
Can do, but it's safer to use the DC socket, which is reverse polarity protected.
Note that you can't draw a lot of current from the 5volt pin (and other pins) when the Mega is powered from 12volt.
About 150mA max before the Mega eventually shuts down and reboots (if you're lucky).
Because with 12volt on V-in, 12-5= 7volt is wasted as heat in the 5volt regulator.
A 7.5volt or 9volt regulated supply is already much better.
A 5volt phone charger connected to the USB socket bypasses the regulator (no heat).
Leo..