Good day,
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 ...?
All help is grealty appreciated
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..
Thank you so much! For 7809 from a 24 volts ,what should be the specs of the capicitor that i should use?
Look at any datasheet of L78xx, there is application circuit. Usually 0.33uF on input, 0.1uF on output. Voltage of both have to be higher than applied voltage, >24V on input, >9V on output.
Wawa:
Because with 12volt on V-in, 12-5= 7volt is wasted as heat in the 5volt regulator.
Or more correctly, 7 volts x whatever the current is, is wasted as heat 
Just note, any switching regulator for a dollar from ebay can do this job quite better.
You can find cap values in the datasheet of the manufacturer who made the 7809 (there are many, with different recommendions). Note that this is a linear regulator, and it will get hot. About 65C with just the current of the Mega (without anything else connected to it). Unless you use a heatsink on the regulator.
Better to use a modern buck converter (little or no heat) to drop that 24volt directly to 5volt.
No extra parts needed, and you can find them for <$1 on ebay.
Leo..