Hello i am trying to make a power supply for my Gauss meter that i am building. I need a +15 volt a +5 volt and a negative 15 volt supply. All three at less than 100 miliamps. I know how to make the +5 and + 15 but how do i make the negative 15. i am hooking the +15 and -15 to a quad opamp 324 so i need a common that will be one neg and one pos form each of the two 15 supplys. The only problem is that is a short. How do i do it. at first i thougt use to different transformers but it still is gonna be a short. At all possibiliey i would prefer to use batteries but the closes thing that i could find is the little 12 volt batteries that are used in car alarm remotes. Any help would be apreciated a lot thanks. My goal is to make a small gauss meter. I would use a built in power supply as a last resort.