I have a small schematic that uses a Nano board. Attached is the schematic. Soon after connecting the USB to program the Nano, the wonderful smell of magic smoke was in the air and I soon realised that the schottky (sp?) diode had a lump on it. I didn't have the 5V input connected.
Note that during this startup that fried the diode, only the components in the schematic were connected and the external OLED, rotary encoder etc where NOT connected.
Should this schematic work ok ?
I am presuming that I have a short in the schematic but I can't see where it is ?
You should not be connecting 5V to Vin. The Arduino needs at least 6.5V here to power the internal regulator.
You can however feed the output of your regulator to the 5V pin if you know it is actually 5V.
Where is the diode that fried? It is not on the diagram.
Sorry jremington don't quite understand the question ? This is the schematic that I drew in Diptrace which I have made a pcb from, where the problem is occurring.
Grumpy Mike. The diode is part of the Nano's board. It sits between the +5v from the Nano boards regulator output and the power coming in on the USB on the Nano board. I believe the idea is that the Nano will take it's power from the highest voltage ? Not quite sure what that implies ?
Regarding the connection. When I powered up the board, it was via the USB connection hence there was no power coming in to the VIN via my connection.
Sorry jremington don't quite understand the question ?
He means how do you know you have wired it like the diagram. You could be thinking it is wired right but it is not. To check this we need to see not only a schematic but a photograph of what your wiring actually is.
When I powered up the board, it was via the USB connection hence there was no power coming in to the VIN via my connection.
That makes little sense? Are you saying that when this diode fried there was no connection to the 5V on the Vin?
It helps to know up front what you have and not spring surprises on us.
Ahh. Now I see. I have presumed that the automatic routing software works. It has worked fine in the past. The pcb routing reads this diagram in directly. No reason to doubt that the board is incorrect but I have attached a image of the board as requested.
From my understanding, which is limited, the VIN connection of a Arduino Nano only connects to the regulator input which then creates the 5v connection from the regulators output which in turn powers the processor chip. The USB goes directly to the 5v connection which powers the processor. Thus the USB 5v does not connect to the VIN connection. As you can see on my diagram I have my 5v derived from the VIN connection and not the 5v coming from the regulator on the Nano. This is where I thought the problem may lay.
If I was to redesign the board I would move the power coming into this board which is labelled "5V In from Buck Converter" from the VIN pin of the Nano to the 5V pin. Is this a good idea ?
If I was to redesign the board I would move the power coming into this board which is labelled "5V In from Buck Converter" from the VIN pin of the Nano to the 5V pin. Is this a good idea ?
Yes.
But why redesign the board? You can cut tracks and put in wire links.
How about a photograph to see if the board has etched correctly?
Aghh. Found a short. It was small and intermittent. Thank you all for the leads. Sorry for wasting your time.
It would be nice if they used a PTC in combination with the Diode though to be fair if fools like me checked whether they had a short before applying power it wouldn't be an issue.
It would be nice if they used a PTC in combination with the Diode though to be fair if fools like me checked whether they had a short before applying power it wouldn't be an issue
All computer USB ports have a resettable fuse so I am surprised the diode fried. If the short was on the cathode side the USB fuse should have opened since the anode is connected to the USB 5V. (VUSB)
