Trying not to fry another Nano

In my first Arduino project, I have so far fried a few Nano (clones) while trying to drive a strip of ws2812b leds. Driving a few (7-20) through usb seem to work fine but when I try to run 144 by battery power the Nano overheats.

Before trying another Nano, I would like to ask if I'm making any obvious mistakes. Please see my images.

Set the buck converter to 5V. Supply the strip directly from that and take a second wire to power the Nano via its 5V pin.

What is the maximum current for your buck converter? Your 144 led strip could draw up to about 7.5A.

What is the component on the left with the 7-seg display? Some kind of voltmeter?

Please post schematic. I can't read the pin descriptions on your image above, too fuzzy. Fritzing has a schematic view, please use that.

Thank you for your swift reply. So, I can simply be underpowered and that would hurt the Nano?

The component with the display is another converter set to 5v out. The idea is that it should feed the leds with 5 v while the Nano is fed with 7 v.

What's that mess? It's not a schematic of you don't join the wires up! Those dotted lines are Fritzing telling you that you forgot to draw a wire.

Tip: use plenty of "power supply" symbols (12V, 5V, GND) around the diagram to avoid a tangle of crossing wires.

Is 2 DC DC converters? Why?

One to support the leds with 5v and one for the Nano at 7v.

Not needed. Nano is also a 5V device. The Nano will draw less than a single ws2812 led would (at max brightness white).

So that thing with the 7-SEG display is also a buck converter?

Thank you, first time for everything includig Fritzing.

So I've read. Then there are also people out there claiming it needs at least 7 v to run.

There are people out there claiming the Earth is flat.

Nano is a 5V device. It contains a built-in regulator, connected to the Vin pin, so that it can also be powered with 7~12V. That regulator is inefficient and easy to overload and burn out, as you have found. But if a 5V supply is available, the Nano should be powered with that, through the 5V pin

Please read this image.

You are supplying the Nano from two sources, even though the Nano SHOULD have protection, some clones do not appear to have this

Tom.. :smiley: :+1: :coffee: :australia:


@abbesnabb it is equally true that the led strip is being powered from two sources: one of your buck converters and the 5V pin of the Nano. No two 5V sources are exactly 5V or exactly equal to each other. There is no way to know which of the two sources will provide what portion of the current that the strip demands, so more could be drawn from the Nano 5V pin than it can withstand. This could be why your Nano burned out. Removing that wire @TomGeorge indicates could have prevented the burn-out.


Here's what I'll try then:

  • Feed the leds with 5 v only (no connection to Arduino power). The leds does not need to be connected to power through the Arduino as I understand it now? They can be fed separately as long as the data comes from the Arduino.

  • Get a proper original Arduino this time.

  • Perhaps I could try to limit the power consumption as pointed out I am potentially underpowered if I run all the leds at maximum white.

Is there a way to physically limit the maximum output (Ampere) or should I do that in the software, I could limit the maximum dim level.

I think I spotted another problem. You are powering the Bluetooth module from the Nano's 3V3 pin. That pin can only supply a very low current, maybe not enough for the Bluetooth module. One of the differences between Nano and Uno is that Nano does not have a dedicated 3.3V regulator on board. The 3.3V comes from the USB-to-Serial chip and can only supply a little current.

In that aspect an Uno would be better then? But would the Bluetooth module fry the whole Nano?

The LEDs must not be powered by or through the Arduino, it cannot withstand such high currents.

The Arduino needs power. Power it from the same buck converter to it's 5V pin. Do not connect it's Vin pin.

A proper original Arduino would have burned out exactly as the clone did.

I asked before what the maximum current of your buck converter is. If that can supply 7.5A then you should have no problem.

If you use the FastLED library, it has that automatic limiting function built in to the library. You just have to set the max current with a function.

Perhaps, yes, it might fry the USB-serial chip on the Nano. Or perhaps that chip will shut down to protect itself and the Bluetooth module will stop working, I'm not sure.

Some hc-06 modules have a built-in 3.3V regulator and so can be run from the same 5V supply as the other components in your circuit. Does your hc-06 module have a regulator?

For example this one:

This module has a built-in 3.3V voltage regulator

So it's better to power the Arduino from 5V pin than Vin pin?

I checked and the converter can supply up to 5A and my battery reads 3.2 A so I guess that's too little. I need to limit it.

I use the FastLED library and I have used the limiting function, set to "FastLED.setMaxPowerInVoltsAndMilliamps(5, 3200);".

My HC-06 says 3.6-6V so that would probably run fine on 5V too which means I could use it on a Nano. Any other disadvantages of using a Nano rather than a Uno for this?

That summarises it absolutely perfectly. :+1:

Absolutely not! Avoid UNOs like the plague. :roll_eyes: Very inconvenient for actual projects.


It is better never to use "Vin" for any purpose in a real project. If playing with a Nano on its own, just perhaps but generally you usually experiment with a bare Nano plugged into a PC which supplies its power through USB so even then that does not make sense.

Whatever do you mean? Given that the switchmode converter is efficient, it will require less than half the current input at 12 V, than is drawn from the 5 V output.

No disadvantages whatsoever. None. Just don't even think of using a UNO. :astonished:

Thank you. Thought the Vin made sense for Arduino's power handling but basically just connecting to 5V pin would be better?