Talking Electronics writes – “A friend of mine who runs an electronic shop wants to install an old cd-rom to be used as a stand alone cd-player in his truck. His problem was to find a suitable power supply for this purpose. A cd-rom uses 2 power supplies, 5 Volts which is used in its logic circuit and 12 Volts for its servos. With these parameters I needed to make a dual regulator that produces 5 Volts and 12 Volts output in one input voltage. Trucks usually uses 2 lead-acid batteries so that will be around 24 Volts.” Link.
HOW TO – Dual voltage regulated power supply for CD-ROM in a truck