I need to get a 9V power source switched down to 5V. I would love if this could be done using a NPN transistor. Supply 9V to the emitter, have a control board I/O pin hooked into the base, and have 5V be passed through the collector when the transistor is closed. I was wondering if I could also trigger the transistor to close when a certain amount of electric is supplied (.01V - 5V) and have it remain open when receiving no power?
Currently I am using a PNP transistor. Supplying 5V to the emitter, base connected to I/O pin on controller, and collector going to devices. I need to supply 5V on the base line to open the circuit. I would much rather supply some type of voltage when the devices need power, not when I do not want them to be powered.