New to Arduino and can't find a Topic on the R3 Uno board, only the R4, so I'm asking here. If this is the wrong place, please let me know.
I believe I have read the Uno board and the Mega board run on 5 volts, but the recommended power supply is 7-12 volts. It says you should not exceed 12 volts as the board may become erratic. It does not say what will occur if you run it on 5 volts. It also says no matter what the supply voltage, the digital IO pins provide 5 volts.
I have 5v, 9v and 12v power supplies. My question is which is preferred and why.
This is going to be a permanent setup to control signals on my model railroad.
All of the power supplies I have are wall warts with barrel style plugs, so I was going to use the barrel jack. For the 5v power supply I could connect the pigtails of a wall wart female plug adapter into the board, which I can do. 5v supply can provide 2 amps.
The Mega board will be operating 8 out of 24 different LEDs from different IO pins at any one time, depending on track conditions. From your description, the 12v would provide the most power, but would need to be reduced from 12v to 5v. The same with the 9v, but would waste only 4 volts instead of 7 volts.
I've gone straight to 5v on boards before, but it was regulated at a true 5 volts. Some of those wall adapters fluctuate so make sure it's providing 5v.
"LDO" is a voltage regulator - it regulates the 9-12V VIN down to 5V.
The downside of this regulator is that it just wastes the extra power as heat.
The more voltage it has to drop, the more heat it generates - so you have to be careful that it doesn't overheat.
Interesting. So does the 5v pin go straight into the grey +5v box? I also have a computer power supply laying around, collecting dirt. Do you happen to have any experience with how well a computer power supply regulates it's 5v output lines. Seems it would be very well regulated as it powers the motherboard, memory and some of the peripheral cards while the 12 volt lines supply the fans, disk drives and other higher current loads.
I always go to the Vin pin, that gives me additional filtering and if a mistook or transient comes it helps the unit to survive. Spikes on the 5V can destroy the processor. It also compensates if the external power supply is not well regulated and also voltage drop on the feed wires.
