If you are looking for DC Voltage Reulator be simple. That can give Current tall about 3A and fine voltage get from 0-30V. As a result please consider this circuit before, it is easy. Because of have no the integrated circuit. Use the transistor is a principle especially the number MJ3001. Usability just fine VR1 for control Volt output and choose the value Current get with S1. The detail is other see in the circuit help understand go up sir.