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I burn my arduino nano 😭 Answered

This is my very very very first arduino project. I followed the attached CDI schematic and tested it on breadboard by connecting USB cable to my computer to test LCD, Button Switch, Brake switch (D2 on nano), (except the relay) everything works fine, until i solder it and test it on my bike, after i turn on the ignition key switch +12v , and pulled the brake switch, the smoke come out from the nano (overheat ??? ) , and now got 2 red led light on nano, ( i think i already killed it 😅). Not sure where i done it wrong, can you guys give me some advice so i can correct it?

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Orngrimm

19 days ago

The problem there (Or one of the problems) is the coil in the relais.
See, an energised coil, if you switch it off, it WILL raise the voltage to VERY high levels (we are talking 100-1000V) to maintain the momentary current. Thats how a cow-fence generates its voltage-Spikes by the way.
Now, see where your coil is connected to: VIN of Arduino. I am quite sure your Arduino doesnt like being fed 1000V-Spikes.
Read up on "freewheeling diode"

Also, Even if your relais never switched, you would kill your Arduino quite fast, as you seem to feed him 12V to VIN.
According to https://store.arduino.cc/arduino-nano --> Specs the Nano is 5V-Supplied. Not 12V. Use a LDO or DC/DC to go 12V to 5V