Adjustable/Variable Voltage Regulator using LM 117
This is the circuit diagram of a 1.2 V to 25 Volts adjustable voltage regulator using IC LM 117 IC.The LM117 series of adjustable 3-terminal positive voltage regulators are able to provide in excess of 0.5A over a 1.2V to 37V output range. They are very easy to handle and require only two external resistors to set the output voltage.
This power supply is able to deliver a maximum of 0.5 A current.The circuit is easy to assemble and provides great results.Resistances R1 and R2 are used for voltage adjustment.Vary pot R2 to get the required voltage.If exact value components are not available try the nearest ones.Parts list is given with the circuit diagram.
- For getting a 1.2 A output current replace LM117 with LM317.All connections are same.
- To reduce min output voltage from 1.2 volt to 0V connect two IN4007 diodes in series to the output ( 1.2 – (0.7+0.7) = -0.2 V ie ; 0 V approx).
- Fit the IC with a suitable heat sink.
- You can use as less as 5V DC as input voltage.No problem but remember the maximum regulated output voltage will also decrease almost by the same fraction. Here a minimum 28V 2A DC input is needed for the IC as shown in figure.
Adjustable Voltage Regulator Circuit Diagram
Note: Potentiometer R2 is 5K (R2 is the pot connected between ADJ and Ground)
LM 117 Pin Out Diagrams