I read that it is best to use a 7v to 12v supply for an arduino diecimla. I am just starting to learn electronics and I have a Ac to Dc adapter that outputs 15v 800mA. If I used this with direct input for the diecimla would it overheat? Also for basic leds and buzzers would 800mA be too much?
I used a 15vdc adapter for a month or so before I found a 9vdc adapter at a thrift store. The 15v adapter caused the Arduino regulator to be somewhat warm to the touch but not hot. I wasn't powering anything externally so this applies just for the basic Arduino board current draw which I guess is well under 100ma or so.
A 15v adapter supplying a full 800ma would cause 8 watts of heat to be dissipated by the 5 volt regulator and it would certainly shutdown due to high temperature. This would not cause permanent damage but of course would not be usable until the current was lowered.
A 9vdc adapter at 800ma would cause the built in regulator to dissipate only 3.2 watts of heat but might still get too hot and shutdown as there is not a heat sink on most Arduino type boards.
So a 15vdc adapter can work for powering just the board, but would most likely shutdown on over temp if more then a couple of hundred ma were drawn from the regulator.
One possible solution is to use an external 5vdc regulator to power higher current loads. There is a Arduino connector pin called Vin which is the unregulated input voltage from whatever adapter is powering the board and could be the input voltage for an external 5vdc regulator which could have a heat sink mounted of the appropriate size for the current needed by the external components.
PS: Keep in mind the external adapter only determines the maximum current capacity, the load (board and external components) determines how much current is actually drawn from the adapter.
Good luck
Lefty
I don't think I fully understand what you are saying but thats ok because I don't think I asked the correct question. That is probably way more complex then for what I am doing. I want to power a 12v buzzer and some leds through the arduino, but I don't get how, because every guide I have read says to buy a 9v power adapter. If my buzzer is 12 volts is it even possible to make it work with the arduino and a 9v power supply adapter. I could just get a 12v wall adapter, but what if in the future I need to power a 14v component. That would be too much for the arduino to handle and I would need to buy another adapter correct? this is what started my question. Basically if the arduino at best only outputs 12vs how is it good for anything but small small components? I don't know enough to say if I will even need many components more then 12 volts, but that is part of my question. I just want to start with basic circuits like this... Arduino controls a resistor - YouTube
Most components needing higher voltages then 5vdc (or 5vdc current in excess of what the on board regulator can handle) use external power supplies, either wall adapters or dedicated power supply modules.
When using external voltages above 5vdc (or 5vdc loads in excess of 30ma or so) there must be a switching device between the Arduino output pin and the external device, usually a switching transistor.
Lefty
Hi,
It is for just this sort of question I wrote my tutorials page, see :-
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html
And work out what power you can draw.
Havy a 15V 800mA supply does not mean that it will give that 800mA,
The board will only take what it needs!
And there is actually a 500mA fuse on the Board!!!
So the board will never take more then 500mA from any external supply
my 2 cent
Patgadget
Montreal
Just the point I make in the latest page at:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html
However, I am not sure where the fuse is? There is a current trip on the regulator and there is a limit on the USB power controlled by the computer but there isn't a fuse on boards I have seen.
USB Overcurrent Protection
The Arduino Duemilanove has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent.
from:
It a resettable fuse (automatic)
OK I hadn't see that design I thought it was the other one.
I have used poly fuses before and they can be a bit slow in tripping out so they are not much good at protecting all electronics from over current most of which will blow faster than a poly fuse.