Programmable power supply with LM317

This circuit can program output voltage by turn-on/off transistors.When transistor turn on the resistor R will be connected to ground for determine output voltage.The maximum voltage of this circuit is 27V when input voltage is 28V.

T1-T4 = 2N2222 or any NPN transistors

This is the output voltage when one of A-D connected to Vin