Arduino Nano with USB and Vin power

I have read questions being asked for Uno boards but not with Nano.

I had my USB lead plugged in at the same time of having 11 volts into the Vin pin. The Nano stopped being able to program anymore even with just USB power. The Nano's regulator got hot. The board is a Chinese alternative. As I thought 11 volts was safe (states 12v max), I thought I was okay.

Anyone else had this problem?

Anyone else had this problem?

How, exactly, is this a programming question?

If I want to program the Nano or use serial monitor to debug with USB connector connected, should I always remove external Vin supply? I read it’s okay with UNO boards but maybe problem on Chinese Nano boards. I just lost a board and wanted to know why. Only indication was the on board regulator got very hot.

I read it's okay with UNO boards but maybe problem on Chinese Nano boards.

Just like any other country, the Chinese are capable to producing great projects and junk. You should not base your conclusions on country of origin.

If the board uses the proper regulator, 12V in is safe. The extra voltage will be wasted, though, AS HEAT. Using a decent 9V power supply or battery (no, not the one you swiped from the smoke detector) would be better than using an 11V power supply/battery.

Thanks Paul. The boards I have do not have any information printed on the regulators so I will add another voltage regulator in to reduce input Vin. Regards

ZOR2:
I have read questions being asked for Uno boards but not with Nano.

I had my USB lead plugged in at the same time of having 11 volts into the Vin pin. The Nano stopped being able to program anymore even with just USB power. The Nano's regulator got hot. The board is a Chinese alternative. As I thought 11 volts was safe (states 12v max), I thought I was okay.

Anyone else had this problem?

There should be absolutely no problems having both an external Vin supply and the USB connection to the computer at the same time. This is true for both the NANO and the UNO.

Going by the official NANO schematic, there is also no problem having the board supplied with both the USB cable and a regulated 5 volt directly to the +5 pin (it won't backfeed to the usb cable on the NANO). This configuration is not recommended on the UNO however, as it will backfeed.

11 volts shouldn't be too high for Vin. If you're not powering a load of add on boards the current draw on the bare nano is only about 25 mA. At a 6 volt differential that's only 125 mW. How much other stuff was your nano powering at the time?

The other thing to look out for is the nominal voltage marked on a supply versus the actual voltage that they put out (particularly on simple DC plug-packs style supplies). Many simple plug-packs are unregulated, and only give approximately their rated voltage at full load. At no (or little) load many of them can put out a much higher voltage. Exactly what type of DC supply was it?

The Nano, official or clone, has very little board area (cooling) to keep the regulator from becoming too hot.

The regulator has to drop the difference between V-in and 5volt.
Heat generated in the regulator is that voltage difference times total current draw (Nano plus anything else connected to 5volt). Lowering V-in will fix this. A Nano can be supplied with as low as 6volt on V-in.

V-in or USB supply should both be possible without problems.
Note that a Nano runs on ~4.6volt on USB supply (Schottky backflow diode).
That could affect things connected to the analogue inputs.
Leo..

Wawa:
Note that a Nano runs on ~4.6volt on USB supply (Schottky backflow diode).
That could affect things connected to the analogue inputs.
Leo..

It certainly has an effect on the 16 key keypads I am using. They have a ladder of resistors connected to the keys. The first 4 keys all came up offset by one key in the table search of analog values. The keypad gave specific values based on 5.0 volts.

Paul

ZOR2:
I have read questions being asked for Uno boards but not with Nano.

I had my USB lead plugged in at the same time of having 11 volts into the Vin pin. The Nano stopped being able to program anymore even with just USB power. The Nano's regulator got hot. The board is a Chinese alternative. As I thought 11 volts was safe (states 12v max), I thought I was okay.

Anyone else had this problem?

I had same situation with my Nano (Chinese clone). When I powered it by USB, it was OK. When I powered it by 12V power supply through Vin, it was also OK. But when I powered it by USB and then connected 12V power supply, Nano just burned (I saw obvious smoke). Now is Nano not recognized by USB.

I have no idea why this happpend.

I noticed a strange thing before I burned it (at least I think)... When I connected (powered) it to USB I measured on Vin 4,2V. I suppose there should be no voltage, otherwise it will backfeed the rest of circuit. Am I wrong ? Is it normal behavior ?

What kind of load (mA) is on the Nano's 5V pin and output pins? That current comes from USB if it's plugged in, not through the 5V regulator.

Old topic, but - Arduino Nano has an interesting bug about USB and VIN simultaneously. No matter Chinese or Italian is. When USB is 1st connected its 5V are provided to the same power supply bus that is VIN passing through a regulator. But, these 5volts saturate feedback transistors which affect the output transistors of the regulator and when now is VIN supplied - regulator burns etc.. Italian variant has a fuse, Chinese one has a semiconductor diode. Both cases are not reliable. There should be two diodes for both supplies which cathodes to be matched on the supplying bus. Our fix for Nano projects is - remove that diode, located below USB plug on other side of the board, then supply it only by VIN even when flash. Not so comfortable, but without burns. Regards.

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PavelPH:
Old topic, but - Arduino Nano has an interesting bug about USB and VIN simultaneously. No matter Chinese or Italian is. When USB is 1st connected its 5V are provided to the same power supply bus that is VIN passing through a regulator. But, these 5volts saturate feedback transistors which affect the output transistors of the regulator and when now is VIN supplied - regulator burns etc.. Italian variant has a fuse, Chinese one has a semiconductor diode. Both cases are not reliable. There should be two diodes for both supplies which cathodes to be matched on the supplying bus. Our fix for Nano projects is - remove that diode, located below USB plug on other side of the board, then supply it only by VIN even when flash. Not so comfortable, but without burns. Regards.

Hi PavelPH,

Is the bug you mention documented somewhere?

Thanks!

sbayeta:
Hi PavelPH,

Is the bug you mention documented somewhere?

Thanks!

I do not know, this is experience based found bug, 5 NANO boards were gone to the bucket. Then we investigate it and saw, it is not sporadic, it is normal with this schematic. No any more burnt boards, after removing that diode/fuse.
Regards!

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