I have 6 5V solenoids connected to an Arduino Uno, each of them with a TIP120 transistor, diode and resistor. Exactly like https://core-electronics.com.au/tutorials/solenoid-control-with-arduino.html but 6 times. I'm using a 9V battery connected to the DC input, as well as USB input to my PC.
Now the problem is that if I activate 5 or 6 solenoids at once, the Arduino seems to get interrupted / lose all power for a second (disconnect sound from the PC and no activity). I've tested them one by one and everything works, but I can activate at most 4 solenoids at once.
What am I missing? Do I need more power?