Is it possible to kill arduino nano with overload?

I wanted to drive a relay with arduino, and I used a BC547 to switch 12V for the relay. But in the relay there was a diode, which sorted out the circuit (thats why I drawed in the wrong orientation)

I know it was a mistake to not use current limiting resistor on Base of the transistor.

Is it possible that this shorted circuit made too much current on the transistor base which killed my arduino?

I made this circuit: Schematic

  • Shouldn't the diode across the relay be the other way round? Like this, it shortcuts the relay, but what it should do, is shortcut the discharge current of the relay.
    – PMF
    Apr 25 '21 at 14:48
  • the backwards diode bypassed the relay ... when the transistor turned on, too much current flowed through the transistor and possibly damaged the transistor, the damaged transistor may have allowed the base voltage to rise to near 12 V
    – jsotola
    Apr 25 '21 at 16:58
  • As mentioned, the frewheeling diode at the relay has wrong orientarion. You also must have a base resistor to limit the current the gpio has to source (you control a BJT just like an led). Some hundred ohm should work for the bc547
    – Sim Son
    Apr 26 '21 at 8:32

Short answer is probably. There is a voltage drop from base to emitter that is about .7 volts. But something still has to contend with the rest of the energy. You might try a different Arduino digital output on the chance that the balance of the processor is working as expected.

I say probably because several things might have happened if the transistor actually turned on. For instance the forward biased (backwards) diode may have allowed so much current to flow through the relay and transistor that the transistor failed first. Or, if the power supply had a low current rating, it may not have had the capacity to burn anything out. As you can see, it is difficult to say what exactly happened with out testing each part individually.

  • The transistor turned on, and something is blown out, i think the transistor but I'am not sure. But the arduino is not working anymore, i can't write code on it, and the code on it doesn't do anything. When i power it, the power LED turns on. And I also can't see any damage on the arduino.
    – ShakeryGO
    Apr 25 '21 at 13:58
  • Disconnect everything from the Arduino then try to program it. Burned out parts can fail open or shorted. If it sill does not program and the Atmel processor is in a socket consider buying a new pre-programmed-with-the-Arduino-boot-loader processor. Or a normal Atmel processor and program the Arduino boot loader your self. Finally, consider starting over with a new Arduino.
    – st2000
    Apr 25 '21 at 14:19
  • I tried almos everything, there is no way to change the Atmel IC. The only way would be to buy a new one, but its sadly more than a week in shipping. I just wanted to know where i made a mistake which lead to damage the arduino. Thnak You for your help!
    – ShakeryGO
    Apr 25 '21 at 14:24
  • I applaud you wanting to learn. But perhaps for the first go you might consider buying a pre-made Arduino compatible relay board with built in drivers and even an optical isolator for added protection. Also, when just starting out, there is no shame in copying an existing working project like this one.
    – st2000
    Apr 25 '21 at 16:50

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