Electronics > Beginners

Bit of a noob, needing project assistance.

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Ian.M:

--- Quote from: rstofer on November 19, 2018, 12:34:44 am ---
--- Quote from: starhawk on November 18, 2018, 11:34:58 pm ---Blinking an LED with a microcontroller is something I do when I need a nap, ugh :=\


--- End quote ---
And if your project still doesn't work, how do you know the CPU is doing anything rational?  It's a rare project that works right out of the gate.

Think about the number of thing that have to work perfectly to get that LED blinking?

--- End quote ---
Specifically, try a blinky LED example, with an external LED + series resistor on each pin in turn of the Arduno that your project needs, as the reversed supply may have blown out one or more of the Arduino's I/O pins.   Its quite likely that the pins that communicate with the SD card have been damaged . . .

rstofer:
I'm expecting more than just a blown SD card.  I'm thinking about a blown USB->Serial Bridge chip and potentially a blown USB port on the PC.  Maybe even the CPU.  But I'm a pessimist...

Again, loading any known working example (Blinky) will prove that a lot of things fared better than I expect.

Thinking about it, why risk another SD card on an Arduino that has been hammered without first proving that it survived?

starhawk:
I'm reasonably certain based on the blinkies on the Arduino that it survived. As for the SD card, I'm actually mildly surprised that it *didn't* survive -- that board has an internal regulator to drop the voltage to 3.3v (which is what SD cards take) and I was using that regulator... it should be the ubiquitous A1117, or so I'd think, which is good up to 18v if it's manufactured within spec. Then again, the board came from eBay, so who the heck knows what's *actually* on there or where it came from. I will finger-test that regulator (and the ATMEGA328 on the Nano) before I do anything further, though...

...I *really* hope the '328 isn't blown, I don't have another good one (I have a questionable one tho) -- and my bank account is such right now that I'd best wait till December or maybe even January before buying a new one.

Meanwhile, my friend announced a little while ago that he would be an hour late...

EDITNESS: the '328 gets moderately warm to the touch... not good. The regulator on the SD card PCB passes the heat test, though. I'm going to put the card in and try and get a response. If I don't, I'll swap in the "maybe it works and maybe it doesn't" Nano that was from another project that botched badly.

LATER EXTRA EDITNESS: to clarify, the '328 gets hot enough to give me side-eye <.< >.> but not hot enough to make me pull my finger away quickly and wave it in the air. It's disconcertingly warm, but not "you could boil water with this" hot.

starhawk:
Got the card... what do you folks think? Should I swap out the Nano, just to be sure? or should I try the SD card first?

Ian.M:
Putting a good SD card in a suspect SD interface on a suspect Arduino risks blowing another SD card.

Why not put the suspect Nano on a breadboard and run a sketch to test each pin in turn can drive high, drive low and return an input value?   That will tell you if your suspect Arduino is good or not.

The one that has a '328P chip that's getting hot is a lost cause if its doing that with nothing connected to its pins.

Use a 330R resistor + a LED for the output tests, first with the pin low and the LED + resistor between the pin and Vcc then again with the pin high and the LED + resistor between the pin and Gnd.
For input tests, use a 10K resistor in series with the pin, and switch the other end of the resistor between Gnd and Vcc.

You can save a lot of hassle writing test sketches if you use a pre-written remote pin control sketch and matching PC app.  Assuming you are running Windows, I like ArduinoMonitor.   The original website's down but here's a direct link to the zip file from the wayback machine.  Unpack it and read arduinomon.html for instructions.

For the SD interface, you need to check its supplying the correct voltage to the card socket and that its logic level translators haven't been damaged.   Do you have a schematic for it?  If not, post good sharp closeup photos of both side of its board, and we can probably advise you what and where to test.  If you need help reducing photos to a size this forum will accept as attachments, ask!

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