Arduino Smoking! PCB short circuit?

[clawed]

Hi all,

I just assembled my first PCB but when I plug in the Arduino via the USB cable the Arduino started smoking so I think there is a short circuit in my circuit design. More specifically I think it has something to do with the toggle switch wiring as I found this only occurs when my toggle switch is in the down position.
I've attached both the circuit diagram and PCB schematic, please let me know if you see where I went wrong, Thanks!

[david_2018]

Did you ever wire this up before having the circuit board made? You have a direct short from +5V to GND when the toggle switch SW1 connects terminals 1 and 2.

[camsysca]

@clawed

please let me know if you see where I went wrong, Thanks!

David got there first.
From the looks of the rest of your schematic, it's highly likely the smoke was from the onboard diode - it might have protected your computer's USB port.

[LarryD]

• Also, driving an Active Buzzer directly from a GPIO is not ideal.
  What current does the buzzer need ?

[clawed]

Hi David,
Thanks for the reply.
Yes i wired the whole thing up on a breadboard, but I guess I didn't know how to convert the toggle switch correctly into a its circuit diagram.

How do you suggest I should change the circuit to amend this ?

[clawed]

Hi Larry,
I think it is around 25 mA, but I didn't seem to have any issues with that in the breadboard circuit. I will need to remake this pcb so I guess ill consider adding a resistor in between if that's what you are suggesting?

[van_der_decken]

pinMode(MODEPIN, INPUT_PULLUP);

[clawed]

Hi van_der_decken,

Thanks a lot for this!

[LarryD]

• If it’s 25mA that’s okay, however, it is easy to add a zero ohm resistor and then later, if you need to, you can add a resistor of say 100Ω

• Some Active buzzers use a coil, these should be avoided as they cause a lot of voltage spikes.

[TomGeorge]

Tom....