1)is it dangerous for arduino the below circuit because GND pin is common with -12V battery pole? 2)is it dangerous for lots of 5v circuit to be grouunded on -12v battery pole?
3)in case i dont connet GND arduino pin with -12v , does arduino works?
4)in case that 1,2 question is dangerous for arduino,does it safe if a connect a diode at P1 mark ?
please expain me the difference among 5?? GND pins on arduino mega 2560. which should i use in order to supply arduino with battery.
All GNDs must be connected, or -12V and -5V as you have drawn it.
The +5 out of the Mega, that will be good for maybe 500mA before the onboard regulator overheats and shuts down.
If you could bring the Vin level down to 6.5V, that would help the regulator run cooler.
Or, set up your external regulator for 5V and connect to the 5V header, with a diode from 5V (cathode) to Vin (anode) so the onboard regulator isn't reverse driven too much.
thank u. so except from regulator that after excessive use will shut down the circuit will not harm arduino.
could you explain the difference among the 5 GND pins in arduino mega?
There is no difference they are all connected to the same potential. Use what ever one is convenient.
Do not put a diode at P1, that will screw things up.
What is the total current draw of the modules.
A Mega has a beefier onboard 5volt regulator than e.g. the UNO.
If it's <~150mA might not be needed to use an external voltage regulator.
Just connect the 12volt to the DC jack.
If you use four or five 1N4004 diodes (0.7volt drop) in series with the 12volt line you can draw even more current.
Leo..
A Mega has a beefier onboard 5volt regulator than e.g. the UNO.
No it doesn't. Both have the same NCP1117ST50T3G rated for 1A max*.
- with good heat sinking and low Vin
NCP1117ST50T3G onsemi | Integrated Circuits (ICs) | DigiKey
Sorry. Sould have said "could have".
My Mega has an 800mA regulator in a DPAK case.
Current isn't the issue here. Power/heat is.
A DPAK case is just a bit bigger than SOT-223
Junction to air 92C/W vs. 156C/W.
What it is on a circuit board is anybody's guess.
Leo..
Grumpy_Mike:
There is no difference they are all connected to the same potential. Use what ever one is convenient.Do not put a diode at P1, that will screw things up.
could you explain more about this??
Not sure what aspect needs explaining?
A diode at P1 will not allow there to be a common ground and depending on the direction of current flow will raise the potential of one side with respect to the other. This will in turn increase the the effective output voltage from one side to the other.
However if you can't understand why you should not do it I am not sure you can understand what it will do when you do.
What was your thinking as to why you should do it? Maybe if I knew that I could offer a better explanation.
kosar:
What was your thinking as to why you should do it? Maybe if I knew that I could offer a better explanation.
I want to be sure that GND pin on arduino will be output only because in case of opposite side a voltage over 5volt will damage the arduino board.
I want to be sure that GND pin on arduino will be output only
No it is not.
because in case of opposite side a voltage over 5volt will damage the arduino board.
I do not understand what that means.