Hi, all I am very much a newbie and only just starting to learn the basics of electronics and I need a circuit to drive a relay and wondered if someone on here might be able to assist. I need to switch a 12 volt relay that has 80 ohms resistance and requiring 150mA draw to hold the coil, the electronic pressure switch that will trigger it provides an analogue 12 volt negative output but is only capable of 4-20mA draw. My first thought was to use a transistor but I don't know enough about them yet to select the appropriate transistor or what resistors would be required to make this operate. Any help would be greatly appreciated.