Ok electronics people.... need a little help with a switch. I have a mailbox that is about 500 feet from any appreciable kind of light and from about this time of year till spring it's hard to see inside the mailbox when you open it in the dark. This has bugged me for about 4 years now. I have a solution but I need help with the on/off switch. I know what I want it to do but I don't know the lingo to find it. Below is a crude drawing of my simple circuit. For the switch, I want it to allow the light to turn on when the door opens, but turn the light off when the door is closed. The two 9V batteries are wired in series to deliver 18VDC to the 12-24VDC LED license plate light. What switch will make this work?