I am trying to power two 12V solenoids directly through the breadboard instead of going through VIN on the arduino. I am using a variable voltage power supply (3V-24V) with a female DC power adapter (jack to screw terminal block) and jumper wires from the adapter to the breadboard. I am unsure why this setup does not work. When I plug the power supply into the jack on the arduino and connect the breadboard to VIN and GND using jumper wires, the solenoids work perfectly. It does not make sense to me why going through the arduino works, but when bypassing the arduino and sticking the jumper wires directly into the breadboard the solenoids do not work.
I have tested the jack to screw terminal block adapter by setting up a simple circuit on the breadboard with an LED so I know that the problem is not with the adapter. Also, given that the solenoids work when connected to power via VIN, I don't think the issue is with the circuit I have set up either.
So, if the power supply, the jack to screw terminal block adapter, and the circuit are all working, then what could the issue be?