Variable power supply using LM317

If you are a beginner in electronics and you want to have good variable power supply using LM317. This is the best project that design for you. It can supply the output voltage 1.2V to 30V at current all range is 1A.

New update Please read below this article.

Variable power supply using LM317, 1.2V to 30V at 1A

This is the first DC power supply in my life that made to use in many projects. It is ideal for those who want to adjust voltage from 1.25V to 30V and currents up to 1A. Which is sufficient for normal use Such as is power supply instead of an one 1.5V AA battery or when you want to listen to music from a 30-watt amplifier that required voltage of 24V 1A, it can be done easily.

In the days before that we commonly used the transistor that is very difficult, large, and probably more expensive ICs. But this circuit can be created with a single IC is lm317 based variable power supply.

The LM317 or LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range,
And has many special features that I like are :
• Output Voltage Tolerance 1%
• Line Regulation 0.01%
• Load Regulation 0.3%
• Prevent the deposition temperature.
• Short-circuit protection.
• Ripple is eliminated with ratio of 80dB
• Maximum input voltage 40V

The working of circuits
Followed circuits below, the transformer T1 is changed a AC 220V down as AC 24V to the bridge diode rectifier D1(1N4001) to D4(1N4001) there is dc voltage into the filter capacitor C1 equal to DC35V
The output voltage from IC1 Depending on the Voltage Adj pin of the IC. Or to adjust the VR1.
The VR1 is control output dc voltage 0V(1.25V) to 30V(32V) or 37V maximum voltage at 1.5A max all range.

Circuit Diagram of My First Variable DC Power Supply 1.25V to 30V at 1A using LM317

Calculate the LM317 output voltage

And we can calculate output voltage equal to:
Vout = 1.25 x {1+ (Rp/R1)
– Vref = 1.25V
– Typically R1 is 220 ohms or 240 ohms as datasheet. I use 220 ohms.
– Normally as datasheet I see them use VR= 5K (Pontentiometer) But I have VR-10K only since it easy to use.
Rp = {(VR1 x R2) / (VR1 + R2)}

Then we test it,Suppose, rotate VR1 to lowest resistance cause Rp = 0 hms. put it in formula above:
Vout = 1.25 x {1+(0/220)}
= 1.25V
But when adjust VR1 to maximum resistance VR1 and R2 are parallel together. Rp = 5.46K = 5460 ohms. test it in formula above:
Vout = 1.25 x {1+(5460/220)}
= 32.2V

Then the capacitor C3 is Better performance filter of IC1.
The diode D5 and D6 ( both is 1N4007) is the protector from external voltage to reverse to makes the damage to the IC1.

How to builds

If you want to see PCB layout and component layout and fully content.
This is first ebook.

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Many begin friends tell me this project difficult to adjust voltage output. so I add potentiometer 1K and parallel 1K-resistor together. then connects them to VR1 as Figure below.

add function thoroughly adjust voltage output

connecting two potentiomers

You will see that we can adjust the voltage at VR2 (new) is 4volts since resistance sum of 500 ohms approximately.
For example, I set voltage is 9V with rotate VR1 is 8.00V and rotate VR2 easily to control the output voltage of 9.00V.
View in video below.

I assemble in the universal box to use easily.



I have old a transformer 12V CT 12V output, but I measure it as 30.9V too much voltage.
It may cause overvoltage DCV as 30.9V x 1.414 = 43.7V. Which can be damaged to IC1 by too much current.

So I modify another transformer 12V CT 12V and 0V 6V 9V 12V output into 21-volts.
as Figure below

This circuit perfectly works, as the video below. I can adjust voltage output is 1.25V to 27V since I use the 21V output transformer.
If you can adjust 24V or 12V CT 12V it causes output up to 30V but IC overheat when a short circuit or overload.

I test circuit with the 12V 8W lamp as a load. A steady (DC) Voltage will not be transferred from 12V.

Add LED Voltmeter display

DC 0-30V 3 Wire Green LED Display Digital Voltage Voltmeter Panel
We can add LED voltmeter to show a voltage level of output.
Mr. Ali Mohammed, ask me how to use 3 wires voltmeter, red, black, and yellow.

It is a good idea. It’s accurate and more convenient.
Block diagram of adding a voltmeter to the first power supply-min

Block diagram of adding a voltmeter to the first power supply

In the circuit diagram, it needs an External DC power supply. We have to build a 9V DC regulator for it.
Please read this idea: Diy digital voltmeter panel meter

We connect a bridge diode (D1 through D4) to SEC (0 and 12V) of a transformer. Then we connect the measure voltage wire in yellow (+) to the output LM317 power supply. And Ground to (-).
Just this we can already read voltage output.

If you use other AC voltage such as 24 volts. You must change:

  • C1 = 1,000uF 50V Electrolytic capacitor
  • R1 = 1K 0.5W resistor

This so saves and easy circuit.

and then…

Low noise LM317 adjustable voltage regulator circuit

This is also LM317 based variable power supply and Low noise, adjustable voltage output: 1.25V to 10VDC (0-12V) from 12V battery source, so simple circuit

If you have a 12V battery. But you have load to use the voltage 1.5V to 9V at 0.75Amp And should reduce the noise as well. Search-based circuits. We use IC LM317K main equipment.

This circuit is DC converter low voltage , 12V from be 1.25V to 10Vdc by can give current topmost get about 1.5A. You should use IC number LM317K because have electric many power more the number LM317K. By should hold heat sink. That have large-sized with. The R4 use for fine decorate voltage output. The C1-470uF 25V(electrolytic capacitors) , C3-0.1uF 63V (Ceramic Capacitor or Mylar Capacitor) , and , C2-22uF 25V , for decrease all noise well. The detail is other , see in the circuit.
circuit source by joe (aircraftdesigner)
Low noise variable power supply using LM317,1.25V to 10VDC

Adjustment DC power supply 1.25-15V Max current 0.5A

This is LM317 based variable power supply that have Voltage output fine the value has 1.25-15V. From by Output current that be valuable about 0.5 amp that 12V and 0.2 amp that 15V. When Volt , from 220V houses reach transformer. It will modify Volt 220V to be 18VAC already to change rectifier circuit. Which D1, D2, C1 and R1 wasp be Full wave rectifier circuit.

For modify DCV to ACV to a signal DCV. It make get a signal DCV that have voltage at pin 3 of IC1 be 20V. From that time DCV signal this reach fight DC Regulator circuit. Which use IC number LM317. This circuit will perform to maintain one’s position Voltage smoothly. Which level output voltage at get this will go out the way pin 2 of IC1. By have capacitors C2 be voltage filter in order that voltage output level of the circuit is will high class modify to follow fining. The performing fee withstands VR1 there.

Adjustment DC power supply 1.25-15V Max current 0.5 amp

Related: Power supply using LM317 Circuits

In addition, You may be not like this. But you may modify these circuits work well too.below.

LM317 Linear power supply Regulator selector 1.5V,3V,4.5V,5V,6V,9V 1.5A

It’s easy to selects voltage output.

0-60 volt DC variable power supply using LM317&LM337

It’s high volt and start voltage at zero! good job.

Best Adjustable DC power supply 3A; 1.2V-20V, 3V-6V-9V-12V

High current for all circuit easy to use.

Dual power supply 3V,5V,6V,9V,12,15V using LM317,LM337

There positive and negative voltage output for all circuit easy to use.
And now you can see

3A Adjustable Regulators using LM350T

This Post Has 121 Comments

  1. (My first Variable DC Power Supply 1.2V to 30V 1A by LM317) R1 was be coal. 🙁 I wonder why?

  2. ็Hi, @mystic

    R1 should not be hot.Please check it shorted to ground or not.

    I hope this guide helps you.

    Thank for your comment.

  3. Yes same prob Admin! and made much coal, i guess atleast a full truck load of R1 coal. R1 is attached from Vout to Adj of LM317.

  4. (My first Variable DC Power Supply 1.2V to 30V 1A by LM317)
    does this really work? because i had a hard time in doing it successfully. the one that i built doesn’t work. 🙁 my output doesn’t have an output of 30v and the 10k potentiometer i can’t figure out how to work it properly. please help me.

  5. P.S. my diode is always buring up. 🙁 please help.

  6. help.. the output is correct but when i connect it to a desired circuit it will low the voltage.. why?????? 🙁

  7. Hi everyone..
    This is madhav..
    Recently i bought an ac-dc power adaptor in which i have an option to vary my output from 1.5v to 12v.
    But when i adjust the knob to 4.5v and check the output using digital multimeter the out put is varying by 3-4volts..
    say for 1.5v it gives 3.6v or somehthing..
    Is this correct reading??? so that on giving load it will show exact reading..
    just tell me whether the problem is with my device or with m y understanding????????????

  8. is the output of this is adjustable from 0-30volts?

  9. admin can i use 0.1uf 50V electrolytic capacitor insteda of 0.1uf 63V polyester. because im having a hard time finding that capacitor.

  10. Dear sir.
    I have copied your schematic and drawn out the pcb i have located all the parts on the pcb except one which you show directly below the 10k pot. i have checked and rechecked the schematic and the pcb all to no avail i can not trace this item what ever it is. Sir would you be so kind and explain it to me. thank you in return. Rob

  11. Dear admin,
    May I ask if I can actually build this circuit in a universal PCB?

  12. what will I use in transformer, 1A or 2A? thank you Sir.

  13. can I use 2A 24V transformer??

  14. hi,Derrick
    Yes, you can use 2A transformer.
    It better than 1A.

  15. i m not gettting output voltage ….is circuit digaram ok??…..i have tried many times

  16. what if… instead of 24 v..i use 30 volts???
    i mean if less or more than 24 V is used then ???

  17. How do you calculate output voltage ???

  18. Hi, Hitman
    Please see in text.

  19. @styles, all diode normally works.
    @maine, You can use it but be careful about polarity electrolytic capacitors.

    @Rob, The pcb is correct but you can use universal PCB it cheaper and faster.

  20. I just finished my first 1.24 to 15V dc power with 2 LM317 voltage regulators but every time I connect my transformer (AC) its producing a smoke on the rectify area . When I use A Dc voltage supply it works fine …can’t figure out the problem. here is the schematic

  21. admin bhai……how the potentiometer being connected in proj.

  22. Hi, rahul
    I solder potentiometer on PCB and Figure the components layout.

  23. The LM317 will shutdown if more than 1.5amp is passed through it.

    It seems a number of people leaving messages of failure to their project are missing this vital safety feature of the LM317.

  24. Pin 1,2,3 Adjust,,, Vout,,, Vin,,,One Tiny Error Can Screw Up This Whole Circuit,,,Please Be Careful Everyone!!! This Circuit Works For Me!!! Thanks admin

  25. What if I need to supply power from 3-25 V using the same structure here? How can I start with a minimum of 3 V output? I tried using zener diodes but they do not function as desired.

  26. Also how is ripple voltage calculated ?

  27. Pls sir help out, i built an amp with TDA2030, but it hums, what could be the reason? It happens to all TDA circuit I hv ever build, I use filter cap of 6800uf still it hums

  28. how can i use this circuit for gettin pure dc of 0-10 volt which will vary according to variation in input 0-230 volt ac ??

  29. that good projet……
    because that application……….
    any project in case all dc project have most of in 30v…….

  30. I just want to know which on of the 217 and 337 transistors outputs has a negative voltage and a positive voltage. Would be appreciated

  31. sorry 337

  32. when i connect it to a 24 v car battery it is overheating and suddenly shut down.

  33. Hi, Kegan.
    Thank for your feedback.
    You can use LM337 negative dc regulator replace with LM317 IC. But you change voltage polarity to negative way.

    In next time I will assemble them because I have more many ICs-LM337.

  34. Hi, Vince

    You can use this circuit to 24V car battery source.

    Please you check the circuit again some part may not correct.

  35. I have made this circuit, its working perfectly.
    I’ve used 15V 1A transformer as input, 100ohm and 10Kohm resistors for 220ohm and 12K resistors respectively. Used both 10K and 1K pots as per the circuit. I am getting 12V dc output. I have also installed a Digital panel voltmeter to the circuit. Its working fine.
    Thank you Admin, for posting this article.

  36. The project works very good but without the VR 10k…….whenever I connect it and turn the circuit on it starts to burn.
    please I need help because I want it a variable power supply

  37. Hi, Kumar

    Thanks for feedback.

  38. Hi,Karim.

    Thanks for your feedback.
    I am sorry for your project do not work.
    Please check wiring parts again.
    In particular,Diode-1N4002 at between Output and ADJ of IC1.
    If you switched lead of diode in wrong polarity.
    It may will cause too much current flow through it to VR-10k with too much current until the potentiometer burned.

  39. Hi,Kegan
    Thanks for your feedback.
    Please wait me in the future I will show you the project that use LM337 in main parts.

  40. Hi admin
    i make this circuit i used all 1n4007 diode & 24 v 1.5amp transformer but R1 get burnout & also 10k pot also plz tell me what is poblem

  41. Hi,Ashok.
    I am sorry you that your project not work.

    Please circuit again.

    Diode-1N4007 across IC1- IN and OUT lead. It may have problem or position of lead not correct. It cause high current flow through it to R1 and VR1 to ground.
    Which make they are burned.

  42. sir i chk those connection but problem is still thr plz help me

  43. @ Ashok
    I think IC1, D-1N007 may be damaged. cause too much current to R1 and VR1.
    But you can test the circuit by follows step below. load.
    2.remove VR1 and D5,D6 before.
    3. Hold the voltmeter at output.
    4.Then short between ADJ and Ground.
    5. Apply AC-power line
    6. If OK the voltage output must be 1.25V
    and R1 not overheat.

    Some times D5,D6 may error. Please check them again.


  44. Sir

    which type of Variable resistor is used for adjusting voltage, as i used it when i move these it burns so it have any amperage for control? as per your instruction i will do it after printing PCB board.

  45. in your above comment in 3 point you said hold voltmeter at output & GND right and ADJ is directly connected to GND that is remove R2? What about R1? I used C2 electrolytic Capacitor as you said polyster?

  46. Hi,Ashok

    I think IC1, D-1N007 may be damaged. so test circuit as above.
    In testing we don’t adjust voltage output.
    We check IC1.
    You remove VR1 then short ADJ and Ground of circuit by may be use wire jumper.
    So you don’t need remove R2 because resistance across it is zero now.
    if the circuit is normal it will be 1.25V at output.

    But R2 burned again indicate that voltage too high which IC1 and D5 are damaged.

    Therefore You check lead of any parts in correct only.
    For example D5,IC1 and more.

    C2 isn’t prblem you can use any type.

    Please slowly check.

  47. how to select transformer using KVA ratings.
    if i want 230V 50Hz ac to down convert it into 24V ac.

  48. hello admin ,,
    can u please give a information about dual polarity linear poewer supply

  49. Hi,Rajan
    This circuit can use AC output 24VAC transformer but voltage DC output too high over 30V.

  50. i have a circuit here output of 32DCV. can i apply it to your circuit to make it variable power supply? thanks 🙂

  51. Hi,.. I’ve build this power supply and its working fine. I’ve added a LED voltmeter for voltage indication.
    Thanks admin.

  52. hi
    check as per your steps voltage gives 8.4V at output. i think IC1 damage
    next time i used another IC it get burns.
    I also chk voltage at in put of IC1 is 36volt.
    please help me what should i do?

  53. Hi sir
    Now problem is solve i think bcause of HEATSINK size & also LM317 duplicate part i used. Now i used Original LM317T with big heat sink that is CPU heatsink it gives values which i want. but when i connect multimeter at out put voltage not stable means value changes for 0.1 to 0.4 regularly increase & decrease can you suggest for stable value.
    Thank you for circuit.

  54. My another question is when i give load voltage get drop output in multimeter. When i used small motor for load voltage drop from 12volt to 2.5volt & motor rotate slowly. what is problem?

  55. sir plz tell me literature survey of these project

  56. Hi,shraddha
    Thanks for your feedback.
    If you read more in E-book may more understand.

  57. sir what kind of IC that is most powerful power supply ? is it LM317 or LM 337? please advise.

  58. sir what is the better IC to be used? is it lm 317 or LM 337? please advise

  59. Hey admin,

    I don’t understand why for the sensitive dial you put 1KOhm resistor in parallel with the 1KOhm pot. I did it this way and the output would only go up to 10.8v max. After I removed the 1K parallel resistor and only had the pots wired in series, the output would go to 35v max and everything works perfectly and doesn’t overheat.

  60. Hi,Arthur
    Thanks for your feedback.
    I am sorry for my English not clear.
    I put others variable resistor in series with VR1 10k to fine adjustable voltage output. We may use 500 ohms but not have it.

  61. Hi, i just wanted to ask, how can i adjust the range from 0 – 30V to 0-15V??

  62. i want to know about 20volt fix dc power supply circuit.plz help me through image of circuit

  63. does this schema work for a transformer 220v/36v 2.5 A ????

  64. Hi Bilal,
    Thanks for your feedback.
    No, you cannot use it because too many voltage output.
    You should use less than 24VAC.

  65. Hi noman,
    Thanks for your feedback.
    This circuit also can apply output is 20V with adjust VR1.

  66. Hey Sir.
    I wonder if i could use 25 or 27 vAC instead of 24?
    and I have built this circuit on Multisim and it works great the only issue im having with it is that whenever i turn my 10k potentiometer all the way up and it gives me an output of 1.2ish VDC my led goes out.( MY LED IS IN PARALLEL WITH THE C3 and IN SERIES WITH A 330 Resistor.) Thank you!

  67. Can I Use LM350T instead of LM317?

  68. can you simplified this ckt diagram,for fixed 30Vdc supply

  69. Why C3 is 470uF when on the datasheet they recomend a capacitor from 1uf to 100uf?

  70. may i know the parts list for this power supply? i might get confused with the voltages for the capacitor. please. thanks

  71. Please can you guide me what is the output current at 3.3v?
    Because i have no multimeter .
    Please reply me fast
    i have stuck in important project

  72. Please tell me what is the correct F and Volt for capacitor C1 , C2 and C3 . TQvm .

  73. Sir, i would like to have a power supply circuit that will provide 0-10 V DC output and another power supply circuit that will provide 0-20 mA. I think this two are a variable voltage source and a variable current source. How do i modify the circuit given above? I would like also to ask where does the multiplier “1.25” from the formula: Vout = (1.25 x {1+ (Rp/R1)). I am getting problem to come up with a minimum voltage of 0 V (from the required 0-10V) because of that multiplier. It would be a great help for the good response and will be highly appreciated. Thank you. -ECE student

  74. Hi John,
    Thanks for your datasheet information, it is tantalum Electrolyte Capacitor type so high quality.
    But I use normal electrolytic capacitor, should use capacitance higher up.

  75. i am bilding almost the same circuit but i don’t have the R2 resistor . my question would it matter if i don’t have it the R2 ? and the transformer i have is 24v 1A but i see your 24V 2A

  76. I bought this device on eBay here’s the link so you can see what I am working with.
    I put it together then I plugged it in but instead of getting 1.5 to 14 volts I am getting 12.2 volts to 15 volts and I am unsure why or what could cause this perhaps a part in wrong or something it didn’t come with full instructions just a circuit diagram and the pcb had markings for the direction of parts. I have another one to build I’m wondering if this one was damaged or something of that nature does anyone know what I could look for to correct it?

  77. Hello,sir
    I can’t get 1 Amp .is there any problem in circuit .

  78. Plz give me working principal of circuit

  79. Hey This project is not helpful but my lm317 ic it’s lot’s of heat i use 4700uF 50v capacitor (help me plz)

  80. Dude you have a flaw in the R3 the 220 Ohm it get very hot under load
    I suggest a 240 Ohm resistor.
    Also the 10k Pot has an issue it burns when adjusted to max voltage
    and also when adjust down to minimum voltage abruptly. Please look
    into it and email me with a answer Please & Thanks.

  81. 1000 uf capacitor burns while giving 21 volt DC

  82. One of The Most Important Pieces Of Test Equipment you can Own

  83. 10k Pot has an issue it burns when adjusted to max voltage
    and also when adjust down to minimum voltage abruptly. Please look
    into it and email me with a answer Please & Thanks.

  84. There is burning problem in the potentiometer whenever I change voltage .I am using 10 uF capacitor in place of capacitor of value 0.1uF.

  85. Pot burnt pls help me

  86. 10k Pot has an issue it burns when adjusted to max voltage
    and also when adjust down to minimum voltage abruptly. Please look
    into it and email me with a answer Please & Thanks.

  87. How to step down(only Amp) DC-5volt 2Amp to Dc-5volt 1Amp?

  88. I have what I thought was a very simple need: from a 12V 10A DC supply, I need to run 5 motors. Each motor needs a slightly different dc voltage (probably between 5-7V) @ < 1 A. so that they all go at the same speed with slightly different loads. So I tried LM317T as per your circuit, but with a 240 Ohm between Output and Adjust and a 2k pot between Adjust and Earth as per various standard designs, the output voltage scarcely changes.
    Can you suggest what I may be doing wrong?

    Kind Regards, David
    (As an anaesthetist, I have a hobbyist knowledge of electronics, but am happy soldering a circuit).

  89. please help me my electronic project

  90. I used a 750mA 12-0-12 transformer …. 20k pot instead of 10k… and 10k resistor instead of 12k… All diodes 4007 and 470u instead of 1000u…. But output voltage is varying only from 8 to 18 instead of 1 to 25…. Anyone HV any suggestions??

  91. 10k Pot has an issue it burns when adjusted to max voltage
    and also when adjust down to minimum voltage abruptly. Please look
    into it and email me with a answer Please & Thanks.

  92. How can design small robot and variable power supply from 0v to 60v

  93. Hi, Mohamed Ali
    Thanks that you are interested to make this project.
    Ohh…I’m sorry to hear that.
    I think you could switch the polarity of the D6-1N4007 diode.
    Or th adj pin is not correct connect or open circuit make output is maximum voltage.
    Now I do not want you discouraged.
    Please check it again.

  94. Can I get the PCB layout of this project? I tried buying the e book but I am unable to pay using my paypal account as well as my cards due to some error in the website.

  95. 10k Pot has an issue it burns when adjusted to max voltage
    and also when adjust down to minimum voltage abruptly.
    Please note I checked the d6 polarity.

    1. Hi, Mina Mamdouh Zaraa Fanous
      Yes, If you put the D6 polarity incorrect, The VR10K will burned.

      1. Hello admin, I just want to ask whether the D6 IN4007 polarity in your circuit images above is connected correctly or not?
        On your update section you add another 1k pot and 1k resistor, may you please update your circuit diagram too? All visitor will be appreciate if you can do that for our better reference 🙂

  96. Hello admin, I just want to ask whether the D6 IN4007 polarity in your circuit images above is connected correctly?
    On your update section you add another 1k pot and 1k resistor, may you please update your circuit diagram too? All visitor will be appreciate if you can do that for better understading reference 🙂

  97. Sir, goodevening. Can I have the voltage value of capacitors in this circuit? I would appreciate if you give me those. Thanks. More power.

    1. Hi, Jom
      All capacitors, You can use voltage (WVDC) = 50V. Specifically, Electrolytic capacitor!

  98. Hi friend..
    Can any one suggest me the updated circuit please..thank you.

  99. How can I add LED to this Circuit? and Voltmeter to measure the output Voltage? Voltmeter has 3 wires Black, Red and Yellow?

  100. hallo,

    habe ihre schaltungen und mails schon vermisst!

    viele grüße


  101. sir any one can help me
    i’m sorry about my bad english
    i also buy an 24-0-24 2A stepdown transformer but it only provides 14V output only why?

    1. Hello Johnny,
      Thank for your question. I am bad English too.
      I am sorry to hear that. First I may check only the transformer again. You should measure the AC voltage is 24V o 24V or 48V total.

    2. it now provide only 14-0-14 as output

      1. Hi, Johnny
        How are you today?
        What uses meaning 14-0-14? Is it 0-14V at output?
        What is the rate of the transformer voltage? 12VAC?
        If you use 14V CT 14V = 28V then rectified to DC is 39V.
        It is not good for LM317.

        I am sorry, too many questions to you. I want to help really.

  102. This circuit works well. Thanks!

  103. Hi all
    Is it work? i will do homework.

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