Unstable NPN switch circuitry

Other Hardware General Electronics
10

azelogose:
ublox connector J1
Pin1 is TX pin
Pin2 is RX pin
Pin3 is (+) pin
Pin6 is (-) pin

This is a schematic using fritzing. In breadboard view this ATmega328 is a real Arduino board, no floating GND pins
Check npn-real.jpg and focus on yellow wire. Why this can cause a problem

That is weird. I expected it was just the chip because it's labelled with the name of the chip, its name is "U1" and it has the crystal pins which aren't available on the Arduino headers. If it was labelled "Arduino UNO" or "Arduino Mega" then that would be easier to understand and we can ignore the crystal pins.

Thanks for sending the breadboard view. However that can't be the breadboard of that schematic you posted earlier. The yellow wire goes from pin 2 on the Mega to nowhere in particular. What did you want us to look at with that wire?