# Adjustable power supply using LM317

```                    I +-------+ O
Vin (+) o-----+---| LM317 |---+--------------+-----o Vout (+)
|   +-------+   |              |
|       | A     /              |
|       |       \ R1 = 240     |
|       |       /              |           ___
_|_ C1   |       |            +_|_ C2      |_0_|  LM317
___ .01  +-------+             ___ 1 uF    |   |  1 - Adjust
|  uF   |                    - |          |___|  2 - Output
|       \                      |           |||   3 - Input
|       / R2                   |           123
|       \                      |
|       |                      |
Vin(-) o------+-------+----------------------+-----o Vout (-)

```
For the LM317:
• 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.