I have an Adruino Mega2560 with Ethernet shield and two Nano's all connected to each other through I2C. The power supply comes from a 12v DC source which is put through a 9v regulator to power the boards via Vin.When I power the Maga through its USB and the Nano's from the 9v everything works perfect, but when I change the Mega to run from the 9 volts the SD card gets corrupted on any attempt to read or write it. I have also tried powering the Mega through the jack socket instead of Vin but still the same problem.
Tried running from the 12V directly? Also did you swap power inputs while the Arduinos were running?
Could be an earth problem between the various power supplies and your computer
You can NOT power a Mega (~70mA) with ethernet shield (~160mA) directly from 12volt.The onboard 5volt regulator will overheat and shut down (if you're lucky).
A 5volt cellphone charger (connected to the USB socket) is a good option.But it all depends on what else you have connected.Post a full diagram.Leo..
I am guessing (lack of proper information) that you power everything (whatever that is) from a lead-acid battery.The most efficient way (minimal heat) would be to bypass all the 5volt regulators on the Arduinos.Use a (reliable) 5volt buck converter, and connect it's output to the 5volt pins of the Arduinos.Leo..
...to change over to a lead acid battery in the even of mains failure
Hi,Please answer post #8.Thanks.. Tom..