I wired up another component via breadboard to my little Uno and everything seemed fine. I was pushing in an SD card when the lights went out on it. None of the little LEDs were flashing, the display was black. I thought I'd screwed up somehow and fried it.
I unplugged it from the USB cable that was powering it, took everything apart and first tested the Uno by itself. It was okay. Then I added each component, one at a time, and everything worked. I pushed in an SD card and it all worked like a charm.
Any idea what might have caused the lights to go out?
Could have been a static charge that momentarily messed up it's internal logic. It's like getting bubbles up your nose. Usually it just makes you to sneeze, but in extreme cases it can leed to unconsciousness. But not often death.
If you find an unconscious victim of bubbles up the nose, it's always worth trying a reboot. They just may come back to life.
A short is a possibility given how I was messing around. I guess that's the obvious thing.
I thought a short might have more consequence than just temporary bubbles-up-the-nose unconsciousness. Does the voltage regulator have protection built in for this sort of misstep? Or for that matter, might the hardware in my computer on the other end of the USB cable limit the current to protect the stupid?
jboyton:
A short is a possibility given how I was messing around. I guess that's the obvious thing.
I thought a short might have more consequence than just temporary bubbles-up-the-nose unconsciousness. Does the voltage regulator have protection built in for this sort of misstep? Or for that matter, might the hardware in my computer on the other end of the USB cable limit the current to protect the stupid?
Depends what shorted. Vcc to ground would likely cause a voltage regulator to take a sharp intake of breath.
I was quite surprised the other week while using an H bridge to drive 18v into a stepper motor. I had inadvertently connected an arduino output pin to the OUTPUT of the H bridge. The H bridge chip exploded yet the arduino got away scott free.
Ah, the glory and wonder of the resettable fuse. Schematic calls for a 500µA fuse. If the amperage exceeds this it opens the circuit. In more practical terms, if you set up a short, the fuse opens, and won't close again until the short is corrected.
It's not a guarantee you won't blow an arduino (and it takes a lot less than 500µa on any given pin to wipe it out!) but it certainly helps.
Tkrain:
Ah, the glory and wonder of the resettable fuse. Schematic calls for a 500µA fuse. If the amperage exceeds this it opens the circuit. In more practical terms, if you set up a short, the fuse opens, and won't close again until the short is corrected.
It's not a guarantee you won't blow an arduino (and it takes a lot less than 500µa on any given pin to wipe it out!) but it certainly helps.
So it does have a dummy protection feature. I was wondering about that. Thanks.
I was wondering if the exposed pins on the SD card controller, which is mounted right below the card slot, could have been shorted by the contacts on a card that was being inserted poorly. But if that were the problem the fuse would have cleared itself without pulling everything apart.
So I could still have a lurking near-short with my current test setup.
John,
Quite right... I'd been typing in cap values literally all day when I typed that, and without thinking put in the µ.
Jboy,
That's entirely possible, but as you said, the fuse would reset itself. You might have just had one little thing wrong, and since you tore down and rebuilt your test setup, the problem went away (by doing it right the second time).
At least whatever happened, the resettable fuse did catch it. I'd also venture to guess that wherever the fault was, it wasn't on one of the digital pins, since those blow under much lower conditions. The fuse in this case is more like the main breaker than an individual breaker.