Is there a limit to the number of components for Arduino Nano?

Using Arduino General Electronics
#1

Is there a limit to the number of pins and components I can use on an Arduino Nano board? My Arduino Nano just popped and released a thin cloud of smoke when I plugged in the USB to test my programme. Now my computer doesn't detect it when I plug it in any more. =(

It was still working perfectly fine until I added one more LED light to one of the pins. I had dangling wires connected to a digital pin and the 5v and ground inputs from the breadboard too. I'm not sure was it because I had too many components connected to my Arduino Nano that it couldn't take it and bursted, or was it because the dangling wires got into contact with each other and caused a short circuit.

This were the components connected to my Arduino Nano:

  • 1 regular LED
  • 1 RGB LED
  • 1 Button
  • 1 Servo

What could have bricked my Arduino? I want to know because I don't want to brick another when I buy my next board.

#2

Never power a servo from the 5V Arduino supply, servos take far more current
than the on-board regulator can supply, and can produce voltage spikes.

For some reason Arduino boards these days seem to come with regulators that
do not fail-safe and shutdown on over-current (judging from a few recent posts).
The Nano is so small there may not be room for a robust regulator anyway.

The information about the boards should say what current you can draw from the
on-board regulator, and you should always check you are not overloading it before
switching on. So yes there is always a limit, and you need to check.

Even small servos can take 1 to 2A peak currents, and more importantly they
can inject high-voltage spikes back onto the supply. You never power a Servo
or motor from the 5V logic supply for that reason - first rule of driving motors
and other inductive loads (relays). There are ways to make it work, but to
play safe never do this.

#3

or was it because the dangling wires got into contact with each other and caused a short circuit.

That would do it for certain!

#4

MarkT:
Never power a servo from the 5V Arduino supply, servos take far more current
than the on-board regulator can supply, and can produce voltage spikes.

For some reason Arduino boards these days seem to come with regulators that
do not fail-safe and shutdown on over-current (judging from a few recent posts).
The Nano is so small there may not be room for a robust regulator anyway.

The information about the boards should say what current you can draw from the
on-board regulator, and you should always check you are not overloading it before
switching on. So yes there is always a limit, and you need to check.

Even small servos can take 1 to 2A peak currents, and more importantly they
can inject high-voltage spikes back onto the supply. You never power a Servo
or motor from the 5V logic supply for that reason - first rule of driving motors
and other inductive loads (relays). There are ways to make it work, but to
play safe never do this.

The funny thing was, those dangling wires, they were supposed to be for the servo. But I took out the servo motor because my code wasn’t really testing it but the LED. And so I took the servo out. But it still popped. I’m really confused and I’m worried that when I get another Nano, the same thing would happen when I connect the circuit back.

But judging on the components that I have connected, are those really too much for the Nano? And what if when the servo is connected? I looked at the Nano specs, but I still cannot figure out how to determine whether I’m overloading or not.

#5

RoyK:

or was it because the dangling wires got into contact with each other and caused a short circuit.

That would do it for certain!

The 3 wires were connected like this:

  • 1 to an digital pin
  • The other to the breadboard along the 5v row
  • The last one to the breadboard along the ground row

So these wires when get contacted will brick the board? Which are the wires that could possibly create a short circuit when get contacted? I suppose the 5v and ground when get in contact merely just completes a round trip circuit and shouldn't do any harm?

#6

xEnOnn:
The funny thing was, those dangling wires, they were supposed to be for the servo. But I took out the servo motor because my code wasn't really testing it but the LED. And so I took the servo out. But it still popped. I'm really confused and I'm worried that when I get another Nano, the same thing would happen when I connect the circuit back.

If you disconnected the servo while it was powered up, that's the worst possible action
you could have done - disconnecting an inductive load that's carrying current guarantees
an inductive spike into your supply.

If not then I suspect a short circuit. Using a breadboard?

But judging on the components that I have connected, are those really too much for the Nano? And what if when the servo is connected? I looked at the Nano specs, but I still cannot figure out how to determine whether I'm overloading or not.

Hmm, the page doesn't mention it, but you can assume something like 100mA is likely
for a small regulator like that. Absolutely no way a servo should be powered through
the Nano, though, that's bad bad news.

#7

MarkT:
If you disconnected the servo while it was powered up, that's the worst possible action
you could have done - disconnecting an inductive load that's carrying current guarantees
an inductive spike into your supply.

No, it wasn't disconnected while it was in power. I took it off before I plug in the USB cable. So there probably wasn't any spikes. Is it more possible that there was a short circuit than it was overloaded?

#8

Did you have resistors inline with the LEDs? How was the button wired in?

#9

xEnOnn:
Is there a limit to the number of pins and components I can use on an Arduino Nano board? My Arduino Nano just popped and released a thin cloud of smoke when I plugged in the USB to test my programme.

If happened as you plugged in the USB? Is there another power supply in the mix (maybe something connected to the breadboard)? To me this sounds like what happens if you have two power supplies and the grounds aren't connected.

Did you see which chip the smoke came out of? Does anything look burned on the board?

xEnOnn:
But judging on the components that I have connected, are those really too much for the Nano?

No.

#10

xEnOnn:
Is it more possible that there was a short circuit than it was overloaded?

It's very unlikely to be the cause.

USB connectors are required to have polyfuses in them. If you short-circuit a USB powered device the USB port will usually shut down until you disconnect the cable.

#11

MarkT:
Hmm, the page doesn't mention it, but you can assume something like 100mA is likely
for a small regulator like that. Absolutely no way a servo should be powered through
the Nano, though, that's bad bad news.

If the power is coming from USB then it shouldn't be going through the regulator.

#12

polymorph:
Did you have resistors inline with the LEDs? How was the button wired in?

Yes, I have 330ohms resistors connected to all LED legs before they are connected to the pins on the Arduino. This is true even for the RGB LED; all the rgb legs had 330 ohms resistor too.

The button is wired this way:

  • One of its pin is connected to a 10k ohms resistor, then continue to a digital input pin and 5v row on breadboard
  • The other is connected to ground
#13

fungus:
If happened as you plugged in the USB? Is there another power supply in the mix? This sounds like what happens if you have two power supplies and the grounds aren't connected.

Did you see which chip the smoke came out of? What looks burned on the board?

When I plugged into the USB, everything was still working for the first 10 seconds or so. During the 10 seconds, I moved my hands to press the button, the LED lighted up, it was all good. And then after that, all of a sudden, there were smoke coming out from beneath the board (it was attached to the breadboard). I'm not sure if it was short circuit because I don't know if I had accidentally shaked or knocked onto any wires when pressing the button, especially when I had dangling wires.

The board is entirely powered by the USB cable. I have no batteries connected to the board.

Although there were no visible burns on the board, the burn mark on the breadboard matches the position of the Voltage Regulator chip. I believe it could be the Voltage Regulator chip that has burnt out. Does this imply anything?

#14

fungus:
It's very unlikely to be the cause.

USB connectors are required to have polyfuses in them. If you short-circuit a USB powered device the USB port will usually shut down until you disconnect the cable.

Does this mean that with those polyfuses in the connectors, even when there is a short circuit, the USB powered device wouldn't get hurt?

#15

There actually isn’t a polyfuse on the nano (like there is on my UNO). There may be a polyfuse in the computer, but if the computer designers decided to allow more than 0.5A at the USB for charging purposes, the polyfuse might just be protection from shorting, not too much current draw. (Don’t be worried about the name “polyfuse”, they aren’t like normal fuses that have to be replaced when tripped. Think of them more like automatic resetting circuit breakers. They will reset themselves when they cool down.)

According to the schematics the voltage regulator should be a UA78M05 on both the v2.3 and v3.0 nanos, which is rated for 500mA. That said, the voltage regulator is a red herring because you are powering the nano by the USB. But, there is a component on the board close to the regulator that all the power from the USB port goes through. This is a Schottky diode, rated for 500mA (it probably should be rated for at least 1A so it doesn’t act like a fuse, but there may have been space constraints). I would suspect that this is the component that released the white smoke (though we don’t know how you were drawing more than 0.5A from the USB yet). Looking at the picture of the nano board’s underside on the nano’s product page on arduino.cc, along the right side of the board starting at the top: there is a vertical empty SMT footprint, a horizontal brown ceramic capacitor, two horizontal yellow tantalum capacitors, and then a horizontal black diode (this is the Schottky diode). Check the two yellow capacitors and the diode for evidence of escaped white smoke. (If it is tough to see by eye, take a macro picture at your highest camera resolution (or a high resolution scan if you have a scanner or an all-in-one printer) and inspect the pictures on a computer monitor.) Unfortunately, with the pin header there, the diode is a difficult $0.35USD part to replace w/o specialized equipment.

If the failure was one of the two yellow capacitors, it might just be a bad tantalum, or a voltage spike. Tantalums usually fail shorted, so this would either trip the polyfuse of your computer’s USB port temporarily shutting it down every time you plug the nano in, or overload and burn out the Schottky diode. Unfortunately, like the diode, the tantalum caps’ placement right next to the pin header make them difficult $0.15USD parts to replace…

#16

The polyfuses are really there to protect your USB port, not the device attached to it. In this case, the Arduino Nano.

#17

Sembazuru:
There actually isn't a polyfuse on the nano (like there is on my UNO). There may be a polyfuse in the computer, but if the computer designers decided to allow more than 0.5A at the USB for charging purposes, the polyfuse might just be protection from shorting, not too much current draw. (Don't be worried about the name "polyfuse", they aren't like normal fuses that have to be replaced when tripped. Think of them more like automatic resetting circuit breakers. They will reset themselves when they cool down.)

Thanks for the really informative post!

Indeed, after the incident, my computer couldn't detect anything I plug into its USB port for the next few minutes before it started to work again. Is this the polyfuses at work?

If the current has to pass through the Schottky diode, you might be right that the Schottky diode is the one that was blown. It is quite close to the voltage regulator and I first thought it was the voltage regulator that was burnt. Still, even with magnifying glass, I can't see any burn marks on the chips.

So it looks like the bricking isn't caused by a short circuit too, but likely a sudden draw of more than 0.5A at the USB port? What are some possible scenarios that could cause a board to draw more than it suppose to? I only had simple components connected to the Nano, I can't quite understand how it would need so much more current that it burns itself. I'm worried that I may burn my next Nano board with the same circuit.

#18

xEnOnn:

Sembazuru:
There actually isn't a polyfuse on the nano (like there is on my UNO). There may be a polyfuse in the computer, but if the computer designers decided to allow more than 0.5A at the USB for charging purposes, the polyfuse might just be protection from shorting, not too much current draw. (Don't be worried about the name "polyfuse", they aren't like normal fuses that have to be replaced when tripped. Think of them more like automatic resetting circuit breakers. They will reset themselves when they cool down.)

Thanks for the really informative post!

Indeed, after the incident, my computer couldn't detect anything I plug into its USB port for the next few minutes before it started to work again. Is this the polyfuses at work?

Yes. That is what I would expect normal behavior from a circuit protected by a polyfuse.

If the current has to pass through the Schottky diode, you might be right that the Schottky diode is the one that was blown. It is quite close to the voltage regulator and I first thought it was the voltage regulator that was burnt. Still, even with magnifying glass, I can't see any burn marks on the chips.

I can sometimes be tough to see, particularly if the component burns out on the underside. I've repaired some boards where I thought a SMT component was blown and/or broken, but couldn't see any damage. It wasn't until I put the soldering iron on one end to start removing solder and then half the component came off with my solder wick.

So it looks like the bricking isn't caused by a short circuit too, but likely a sudden draw of more than 0.5A at the USB port? What are some possible scenarios that could cause a board to draw more than it suppose to? I only had simple components connected to the Nano, I can't quite understand how it would need so much more current that it burns itself. I'm worried that I may burn my next Nano board with the same circuit.

You also said previously regarding the dangling wires:

I suppose the 5v and ground when get in contact merely just completes a round trip circuit and shouldn't do any harm?

Actually, yes. Accidentally shorting the +5V line to ground while the circuit is being powered by USB could conceivably blow out the Schottky diode.

An interesting experiment would be to attach an external power supply (at least 7VDC, 5 AA batteries in series or a 9V battery would work) to the Vin pin. This will then power the circuit through the 5V regulator. If the problem is just the Schottky then your nano should work. Before trying that, check with an ohm-meter to make sure that the +5V pin isn't currently shorted to GND.

If the only problem is the blown Schottky, then you can continue to use this board with USB for data (programming, and Serial I/O) like normal, you would just need to have an external supply of at least 7V on the Vin pin.

#19

After a little more checking, Sembazuru is right that if I use a battery, the board can be powered up. I tried other stuff like uploading programmes to it and they work too. So this probably implies that the Schottsky diode was blown.

So this was likely caused when the board was attempted to draw more than 0.5mA from the computer and it blew up itself, right? Would a 5V wire touching the ground wire cause this to happen?

#20