What is the max current that the Duemilanove's 5V regulator can source without the risk of overheating? I want to power some stuff off of the 5V pin and it will bump the total current the regulator is sourcing to a little over 200mA. The regulator itself is a MC33269-D that is rated for 800mA, but I am not sure how it will fair with the way it is mounted on the Duemilanove with what looks like a fairly limited stock heatsink.
How hot the regulator gets is as much about the supply voltage as the current its supplying. If it only has to lose a couple of volts (7v supply) it stays a lot cooler than if has to lose 7v (12 v supply). Using a Wiznet ethernet shield the consumption is approaching 200mA (150 for the shield, 30+ for the arduino), it gets pretty warm with a 12v supply, its a lot happier with a supply that runs around 8.5 Volts. Quick and dirty is to put a number of rectifier diodes inline and let them dissipate some of the heat before it gets to te Arduino.
Thank you for the response. I am going to try and run everything off of a 9V lithium battery but it may be too much current for it. If that is the case I will have to get a battery pack or just run from a 12V source. I think I am going to power my circuit off of the VIN pin with an external LM340 5V regulator. This way my external circuit won't rely on the Arduino's regulator.
I think I am going to power my circuit off of the VIN pin with an external LM340 5V regulator. This way my external circuit won't rely on the Arduino's regulator.
There is a polarity protection diode nominally rated at 1 amp wired between the Arduino's external power jack and the Vin pin, so unless you jumper around that diode you will have to keep current consumption under 1 amp for both the Arduino board plus what ever you plan on powering from the Vin pin.
Lefty
Thanks for the response.