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I was working with Arduino and Xbee with LED, circuit LED + Servomotor and doing testing for 5 hours (not continuously).

Then once I omitted the Servomotor circuit and I connected flex sensor, which required connecting 10k Resistor and connect it the laptop as usual, smoke came out of the board (from USB side). I disconnected it immediately, but now the board doesn't light up and the 5V gives 1.5V.

Is there any chance to fix the board?

I discovered that the B2 diode cracked in the middle, the picture is showing a good Arduino Nano.

I found a very similar in this post about dead NANO

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  • If you can identify which components have fried they can be replaced. Or you just get another board.
    – Majenko
    Sep 30 '16 at 22:41
  • I don't know unfortunately, I really don't know what cause it.
    – O2M
    Oct 1 '16 at 8:01
  • I figured out that the chip B2 (next to the USB) exploded and cracked
    – O2M
    Oct 1 '16 at 10:21
  • B2? Are you sure you don't mean D2? I don't know what a "B?" is other than a battery, and it's not that.
    – Majenko
    Oct 1 '16 at 10:22
  • Although I don't see a D2 on the schematic, only a D1. Tell you what - maybe a close-up photo of your board showing the broken component would help...?
    – Majenko
    Oct 1 '16 at 10:28
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If my understanding is correct, the flex sensor was connected between 5V and GND. This acted like "short circuit" and should not have burned the AVR, but only the power supply side. If you have a multimeter and some soldering skills it should be possible to fix the board.

Supposing you have an genuine arduino UNO, here is a schematic but it may not be the right version

  1. Remove the MCU
  2. Check voltage between GND and XUSB is 5V (if not either your USB port is burned or you have a short on the board or a component)
  3. Check voltage between GND and USBVCC is 5V (if not, replace the fuse)
  4. Check voltage between GND and +5V is 5V (if it's still 1.5V as you mentioned, try replacing transistor T1 but I do not understand why it would burn. If it's 5V replace the MCU)

EDIT for Arduino Nano

I did not understand you had a nano board (schematic)

The component "B2" you mention is the diode D1 (MBR0520). It burned because of the short circuit you created and nothing else should be defect. It acted like a fuse. Simply replace it and it should be fine.

If you are VERY CAREFULL not to overload the nano with external circuitery and never bring external 5V you could just remove it and make a little solder bridge (waiting for replacement part)

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  • The circuit is correct (as I think), but here is was I just noticed, B2 chip is cracked. I don't know what I can do to it
    – O2M
    Oct 1 '16 at 10:23
  • soldering a bride over the diode? do yu think I can use USB port normally after that?
    – O2M
    Oct 1 '16 at 12:29
  • Yes a bridge over the diode should work but plese be carefull if you do that. The diode is only here to protect USB port if external power is applied (or as fuse as you demonstrate ^^) and a short will work. BUT DO NOT APPLY EXTERNAL POWER SUPPLY IF YOU DO THAT
    – Julien
    Oct 1 '16 at 12:35
  • external power is power by battery right? .. because I read somewhere that it may affect the Laptop's port as well if I shorted the diode and connected the NANO by USB. do yu hav idea about this?
    – O2M
    Oct 1 '16 at 13:31
  • @O2M I'm electronic and software engineer, shorting the diode if you connect nothing else than 1 USB port to your Nano is no risk at all for the PC and the Nano. Diode is here to prevent current flowing into the USB port if you connect external power (battery or other). Your short circuit experience with flex sensor shows that the diode also protects the computer USB from overcurrent by burning (this protection is only side effect, the diode could be shorted instead of open). Thus shorting the diode should only be a temporary solution to confirm nothin other is broken and it should be replaced
    – Julien
    Oct 1 '16 at 14:20
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The Nano has mainly surface-mounted devices on it. You need to be quite skilled to remove faulty ones and replace them, without special equipment.

By the time you have identified which one needs replacing, removed it (no easy task if it is the processor) and replaced it, it would be easier and probably cheaper to just buy a new board.

You may well have fried the main processor (Atmega328P) which I see with a quick search is selling for around $7 to $8 in one-off quantities, whereas you can buy the entire Nano for around $13 for a genuine one, or around $9 for a clone. It just won't be worth the trouble.

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  • hello sir, the problem is that the circuit seems correct and there is no short circuit anywhere, i'm really afraid to by a new one and burn it as well since i'm going to build the same circuit again. Can you identify whether the cause of burning is by the circuit or no? The flex sensor required 10K-R and lilypad Xbee board both connect to the 5V. The board orginaly was working fine as I said, but once I removed Servo and I connected the flex Sensor circuit this what happened.
    – O2M
    Oct 1 '16 at 7:57
  • I figured out that the chip B2 (next to the USB) exploded and craked
    – O2M
    Oct 1 '16 at 10:21

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