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>>

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I always try to make Electronics Learning Easy.


  1. Hi, shahin
    thanks for your comment.
    Please find power supply switching on mysite better.
    or get email news member You can always learn new circuits.

  2. Hi,thanks for your comment.your website is beter.
    good lack

  3. can u give me a design and a pcb layout of short circuit protected power supply with IC that has a 5v as an output?

  4. Hi, ivan

    Thanks for your feedback,.
    LM317t have short circuit protection.

  5. John Sabalboro

    Sir, its John from the Philippines, What if I want to add 12v and 15v output? What resistor do I need add to work it? Pls. Tell me sir I’d love to do this… Thanks

  6. Nikhil

    sir can u please suggest me a 5v dc to 1.5 dc converter?

  7. Arman

    hi.tanks for god informations.
    can you send mi all project power switching? tanks

  8. rod

    why is it that the 20ohms resistor getting burned, how many watts resistor should i use, thanks

  9. Hi, rod
    D6-1N4002 may be connected to the wrong polarity. or switch direct current to R-20 ohms.

    Please check parts again.
    Good luck.

  10. Greg Banks

    Hi there. I built a very similar supply for my self many years ago. Suggestion for you, make sure the selector switch is a ” make before break” type. If it is the more common break before make, then as you change the voltage selector from one setting to the next there is a brief moment when it is open circuit. This results in the maximum voltage being present on the output for a moment too. I destroyed a low voltage circuit on my unit ( maximum voltage 18v) switching from 3 to 4.5v You might need to shop around to find a make before break type. But I’m sure the bigger suppliers ( RS or Element 14, etc) will have them. Well worth the little extra money.

  11. duTch

    So this is interesting- with electronics, I know enough to be dangerous, so ¿¿ if I want to reduce a ~6.0 -7.4 volt input to 3.6 – 4.2 volt usable output, is a ‘completely’ different story yeah?..but not so complicated, how will I achieve this?…and thanks for the output, duTch

  12. MarK

    the selector Switch can be replace by Potentiometer?

  13. The Selector Switch can be replace by a Potentiometer?

  14. Víctor Venegas Flores

    Buen dia.
    Tengo una F.A variable con el LM317, de 1,7 a 27 vc., como sabemos nos da un máximo de 1,5,Amperios;como puedo hacer para agregarle más corriente (hasta 3 Amperios), se que se le puede agregar una resistencia y un transistor de potencia.
    Les estaré muy agradecidos por su respuesta.

  15. Andrejs

    When you are switching a voltage from one to another, the rotary switch will end up in middle position for a short undefined period of time, which might (will) f*ck up the whole thing, and potentionally might burn circuit, since R3 will be floating, and as a result LDO will give out a high voltage spike.

    So, a question: how can I implement a protection for this without redesigning a circuit for having a parallel (to rotary switch) resistor?

    • Hi Andrejs,
      Your question is very interesting. You are observant.
      Right now I can’t answer your question perfectly.
      But I have experience. When I twist the switch halfway between the 2 voltages, it causes high voltages at the output. So we have to unload the load first.

      Your point is interesting. I like it a lot. If you can design it then Please don’t forget to share with me.

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