Why nano get hot and smoke came out from nano (Not genuine arduino nano)

Hello guys! This is my first post here.

I recently start my very first nano project. I tested it on breadboard by connecting the usb cable to my computer to test the Nano,LCD, everything works fine until i connect it to 12V and it getting HOT and Smoke came out from my nano (now got 2 red led light up at the same time) and when i hold the LCD i get electric shocked :o

so my question is, what caused these issue?

  1. Did not connect ground wire properly?
  2. VIN and Gnd connect together due to bad soldering caused electric shock?
  3. .....?

You need to read a bit about Automotive transient protection. You can easily get 40V to 60V for short amounts of time. It gets even worse when you are a long way from the battery. Electronics for taillights needs to withstand +100V and -300V, because the long wires have an inductive characteristic. So, when they are switched off, they create a reverse current.

Google “Automotive Transient Protection” and look for application notes from semiconductor companies.

The transistor needs a base resistor say 330R.

I missed the relais. You have your own transient generator. When you switch off the relais, the magnetic field in the relais will colapse and create high voltage transient. You will need a flyback diode for that.

That all said, it doesn't explain why the nano was instantly trashed when you connected 12v. My guess would be that you connected the 12v backwards, and you should thank your lucky stars that it didn't destroy the laptop too.

DrAzzy:
That all said, it doesn't explain why the nano was instantly trashed when you connected 12v. My guess would be that you connected the 12v backwards, and you should thank your lucky stars that it didn't destroy the laptop too.

Hi DrAzzy,

Thanks for the reply!

There are 2 wires "Red White" and "Blue White" from the sensor, and am not sure which wire is +12v, Hence i connect the "COM" from the relay to "Blue white" wire. After that, I touched the sensor and smoke came out from nano immediately...

6v6gt:
The transistor needs a base resistor say 330R.

Hi 6v6gt,

Thanks for the reply! Do you mean add a resistor between 2n2222 and nano??

D5 pin connection need a resistor indeed. At least 250Ω, something like 1k or 2k2 will probably do great depending on the coil current.

Relay needs a flyback diode across the coil, or it's bound to destroy other parts of the circuit the moment you switch it off.

Better connect the relay coil ground directly to the 12V ground, not via the Arduino as your circuit suggests.

Diy_World:
Do you mean add a resistor between 2n2222 and nano??

Yes.

Also, your relay is marked 24V. I think that is the coil voltage. So it might not work at 12V.

wvmarle:
D5 pin connection need a resistor indeed. At least 250Ω, something like 1k or 2k2 will probably do great depending on the coil current.

Relay needs a flyback diode across the coil, or it's bound to destroy other parts of the circuit the moment you switch it off.

Better connect the relay coil ground directly to the 12V ground, not via the Arduino as your circuit suggests.

Hi wvmarle!

Thanks for the reply!

I have added the flyback diode ( Is 1N4007 good for this ?)

Schematic looks fine to me.

Klaus_K:
I missed the relais. You have your own transient generator. When you switch off the relais, the magnetic field in the relais will colapse and create high voltage transient. You will need a flyback diode for that.

Flyback diode - Wikipedia

Hi Klaus_K,

Thanks for the reply!

Yup! I have added a flyback diode at the relay! :wink:

What are you trying to do, exactly? I'm concerned looking at how the relay and position sensor are wired.

You need ground of the arduino connected to ground (-) of the car supply.

Looks to me like an engine immobilizer !

DrAzzy:
What are you trying to do, exactly? I’m concerned looking at how the relay and position sensor are wired.

You need ground of the arduino connected to ground (-) of the car supply.

Hi!

Yes! I have a ground wire (GND on nano ) which will connected to the Battery (-)

What will happen if i connect the “COM” to the wrong wire???

I was asking what you intend for that system to do with the crankshaft sensor thing, rather than what the overall goal is (I do electronics; I don't know a motorcycle from a hole in the ground).

It looks like right now you have the relay wired to, when it's in one position, short out the sensor; this would block output from the sensor from getting back into the motorcycle's electronics (probably making it think that the engine was stopped). How does that sensor output data? If it works by connecting the two pins once per revolution (eg, hall effect sensor), one could spoof that with a setup like that - except that a relay isn't fast nor durable enough for this (they switch relatively slowly, and are rated for a limited number of switch closures over the life of the relay which would be rapidly exhausted even if it could switch on a time-scale comparable to the RPM of an engine), and you'd also have to disconnect the sensor, as it would interfere with the signal you're trying to send.

12volt is too much for a Nano. There have been many previous threads with Nanos smoking at that voltage.
The Nano also has a design fault, where the regulator blows up (and smokes the Nano) if 12volt and USB are connected in the wrong order.
Much safer to use a 12>5volt buck converter, and power the Nano with that on the 5volt pin.
A cigarette-style USB charger should be car-safe, and can be connected to the USB socket.
Leo…

may be the 12V is higher voltage for this

Wawa:
12volt is too much for a Nano. There have been many previous threads with Nanos smoking at that voltage.
The Nano also has a design fault, where the regulator blows up (and smokes the Nano) if 12volt and USB are connected in the wrong order.
Much safer to use a 12>5volt buck converter, and power the Nano with that on the 5volt pin.
A cigarette-style USB charger should be car-safe, and can be connected to the USB socket.
Leo..

Hi Wawa and Faheemc2019,

Thanks for the reply! in this case, Would it help if i add a Voltage regulator 7805?

Something like this ( +12V > 7805 > +5V )

Hi
OPs last diag;

What is the "sensor" switch?

Tom... :slight_smile: