R2 = (192 x Vout) – 240, where R2 in ohms, Vout is in volts and must be at between 1.2 V and 35 V. Vin should be at least 2.5V greater than Vout. Select a wall adapter with a voltage at least 2.5 V greater than your regulated output at full load. Maximum output current is 1 A. Use proper heatsink for LM317 if it has to dissipate more than 1W. The tab of the LM317 is connected to the center pin. Link