LM317 Regulated Power Supply Voltage Select to 1.5V,3V,4.5V,5V,6V,9V 1.5A

Normally begin to learn about electronics power supply from the battery.
For example, 9 volts, 1.5 volts, 6 volts etc.

But there is a disadvantage that when using battery power is discharged. I need to buy a new one. Consume more.

We should the dc power supply have a choice of AC voltage. Which it must provide an output voltage as used often is 1.5 volts, 3 volts, 4.5 volts, 6V, 9V, and the current is about 1 A.

LM317 voltage selector

When we view many circuit ideas, I found that as figure this below (number second the power supply projects in my life) have the best fit.

We use a dc voltage regulator number LM317T is the heart of the circuit. Featured, is the constant voltage.

Low noise. Almost equal to the voltage of the battery. And short-circuit protection as well.

How it works

When we push power switch (S1) on, the AC-line voltage will pass through a fuse F1 and come to transformer T1 to reduce AC volts down to 12 volts.

Then this current flow through the bridge diode model (D1-D4)-1N4001 to full-wave rectifier as DC current.

And through C1 to filter current to smooth up and has C2 filter ripple signal before into LM317.

Learn: How to use LM317 Datasheet pinout and example circuits

LED to display power on the circuit, with R1(2K) currents to reduce it.

1.5V, 3V, 4.5V, 5V, 6V, 9V adjustable power supply instead of a battery
1.5V, 3V, 4.5V, 5V, 6V, 9V adjustable power supply circuit instead of a battery

Here is the step-by-step process.

  • The output voltage is determined by rotating a selector switch S2 a level voltage 1.5,3,4.5,5,6,9 volts respectively.
  • C5 (10uF) control impedance and reduce a transient at the output of IC1
  • C3 (10uF)- help to reduce the ripple before it is amplified when the output voltage rises up.
  • C4 (0.1uF) reduces the ripple at the output.
  • D5 and D6(1N4001) for protects IC1 from the discharging of C3 and C5 respectively. In case the input of IC1 is shorted.

The maximum output current about 1.5A depends on the size of the transformer. We should choose the size of the 2A. Or size 1A. For those who want to 1A output current only.

How to build this project

This project is not used many components so can assemble on the universal PCB board. But can make a PCB as Figure 2.

Then, the wiring for circuit wiring and various components can view of the example in Figure 3.

What to look out carefully for is the polarity of the electrolytic capacitors and Diodes correctly. The pin of the IC is not an error.


Figure 2 the PCB of this projects


Figure 3 the components layout and wiring to all parts

Others of LM317 voltage selector

Also, you may like these projects below:

My first Variable DC Power Supply, 1.2V to 30V at 1A using LM317
It’s easy and as cheap as possible.

0-60V/0-30V DC variable power supply using LM317 & LM337
It is high volt and starts voltage at zero! good job. Read more>>

Best 3A DC power supply, adjustable 1.2V to 20V, 3V-6V-9V-12V
High current for all circuit easy to use. Read more>>

Dual power supply 3V,5V,6V,9V,12,15V with LM317,LM337
There positive and negative voltage output for all circuit easy to use. Read more>>


I always try to make Electronics Learning Easy.

Apichet Garaipoom

I love the electronic circuits. I will collect a lot of circuit electronics to teach my son and are useful for everyone.
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