Use common voltage regulator ICs to do it. Their datasheets shows their minimum input DC voltage requirement. Of course a transformer with a center-tap must be used to make both polarities and a rectifier bridge must be used plus a main filter capacitors. Since you do not need any current then it will be a small and simple project.
. Of course a transformer with a center-tap must be used to make both polarities and a rectifier bridge must be used plus ... filter capacitors. Since you do not need any current then it will be a small and simple project.
Does a centre-tap transformer imply two equal voltages? He could use a "12V" transformer in phase with a "5V" transformer [I am too lazy to calculate the minimum Vac].