I would just like to share my experience regarding the Mega Pro Mini CH340G.
I have had a lot of trouble with a few boards fried, apparently without any reason.
I finally found this post: https://forum.arduino.cc/t/powering-the-arduino-mega-2560-pro-embed/643076/3
and it clearly points out that the Pro Mini must be powered with 5V, into the pin labelled "5V"., contrarily to what is frequently said on the technical specifications, suggesting to power this board with [7-9V] in the Vin pin.
The onboard voltage regulator seems to be the problem, and since I have used 5V into the "5V" pin, there is no more issue.
I have not found this information (max current draw), but I have read other testimonials saying that the onboard voltage regulator dies frequently as soon as you connect another device to the board, being totally unable to feed anything else that the board (without any other device connected to the board).
The specs say that the Vin input voltage should be [7 to 12V], I have reduced it to 9V but a few boards died, as said by other persons.
The main device connected to the boards were a LCD screen (via I2C), that draws 10mA (I have measured it this afternoon). There were also a Reed relays board, but asking only 10mA during 0.5 second, not often (there can be many seconds or minutes between two relays actions).
So today I have placed a small 5V power supply nearby the Mega Mini, in order to feed it with 5V, connected to the "5V" pin.
In a large part of the webistes, this "5V" pin is described as a "5V output", only a few of them have specs saying 'Input or output'.
This new small P.S. transforms my 12V source in 5V , via a 7805 equivalent. I have added a small basic dissipator to the 7805.
I have measured that the [Mega Mini+LCD screen] draw 80mA with this 5V power supply. This combination has worked continuously during 8 hours: the 7805 gets tepid (not cold but not very hot), so I believe that it should be reliable even enclosed in a small chassis.
I will make it working continuously tomorrow, but I believe that this should solve the issue.
I think this is quite well known, or at least should be considering the amount of time I do spend here warning people not to use "Vin" or the "barrel jack" for any serious project - one where other devices and modules are connected.
So it is not at all surprising that you have found just one of my posts from 20 months ago. There have been many more before and since.
I still thank you very much for this information: since then, I have solved the frequent problems that I had with "fried" Mega(s) powered with 9V....
Thank you again
