I've got an Arduino NG, (which I know is quite similar to a Diecimila), and I'd like to know a bit more about how, exactly, the power supplies should be used.
I don't have a separate programmer, so I'm using the USB port for all of my programming. But. I'm extremely leary of drawing too much current from the computer as I move past driving LEDs.
So, I want to use power from the 9VDC port, but I want also to use the USB port simultaneously for programming. (While ignoring the 5VDC of power.) But... that means I have two potential power sources, and it's not clear to me that this is a safe mode.
If I switch the power select jumper to "Ext", does this mean that the USB-power lines are -completely- separated from the rest of the board? Can I leave both the USB port and DC power in plugged in safely?
If it's safe to have both power supplies hooked up with the jumper on EXT, I'd expect this to be the normal way people are working. The ease of programming while simultaneously driving larger motors or lights would seem to be quite desirable.
I've seen a couple of remarks that are somewhat tangential but appear to imply that this is true - but I'd really appreciate someone addressing this issue directly. Even if it is just "I've done this, no magic smoke was released."
You SHOULD be able to use external power and USB data connection at the same time.
it doesn't really matter much, because the sort of power you can draw (legally) from your computer's USB port is "about the same" as the arduino regulator for external power can provide (about 0.5A)
For motor control of large or numerous motors, you can (should!) power your motors only from a separate external supply with only GND common to the arduino. Exact wiring details will depend on the type of motor you're using. There are probably examples in the playground.
Using a USB hub, and/or an add-on USB interface card, will provide some level of extra protection for your computer's expensive motherboard. But USB is designed as a connection for "consumers" to use, and most reputable computers should have relatively robust USB ports. Maybe.
Drat. Is the power limit on the external regulator something I could improve by "just" desoldering the existing regulator and slapping in one with a higher amperge rating and/or adding one of the modest regulator heat sinks?
I'm basically working through a 40 project book and trying to see if I can run all of the examples simultaneously by using shift registers, recoding, and any other multiplexing tricks. The motors are neither large nor numerous (a servo + a stepper), they're in the 'cheapest available example' category.
No need to beef up the on-board regulator, not that that would be a very practical effort. Just acquired a external regulated +5vdc power supply for all the needs of the external components you want to power. As long as the ground of the new +5vdc power supply is wired to the Arduino ground pin, the external components don't care. Many have utilized old PC power supplies that are available for nearly free and have the advantage of also having +12vdc from them, good for motors and other higher power components and loads.
