Here, we present a classic adjustable power supply circuit which is based on the LM338. LM338 is an adjustable 3-terminal positive voltage regulator and it is capable of supplying in excess of 5A over a 1.2V to 32V output range.
The output voltage can be set at a desired value from R1 potentiometer. Vout can be calculated from Vout=1.25*(1 + R1/R2). You will not need to perform any calculations if you just use a voltmeter in order to monitor the output voltage in real time.
Besides LM338, you can use the almost identical LM138. The two regulators differ only at their operating temperature range. Both regulators are available in standard Steel TO-3 and plastic TO-220 packages. Those with a T suffix are packaged in a TO-220 plastic package and those with a K suffix are packaged in TO-3. T and K regulators are not directly pin-compatible, so we have designed a PCB which accepts both types threw cable connections.
In order to build the unit, you will need to download the PCB layout as provided here. Build your PCB and solder the components as indicated in the Components Placement Guide. Use a large heat sink for the regulator and enjoy your homemade power supply unit!
Posted by: A.G