Power Supply (+-5vconst & 0-+-12v Variable)

the purpose of this instructable is to make a power supply that can give output of +-5v constant and 0-+-12v variable output.
we often require dc voltages for our experiments then why spend money on cells or rechargeable batteries .why not build a power supply that takes ac(220vrms) and gives required output.

the empty space in the PCB layout is for transformer (in case of any issue)

and please rate it   :)



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    14 Discussions


    1 year ago

    I made a psu with lm317 using the common sschematic.i used your coarse fine adj method as well.resistor values are 1k and 10k pot with 1k pot for fine adj.
    However the voltage cannot be adjusted using both pots.its always 10.6v with 12v vin.
    I replaced 220R resistor to 10k and 1k pot and that reduced the voltage.then used 5k pot instead of 10k and 1k pots.its worked but max voltage was 8.5v.so i removed 1k resistor(R2) and placed 470R resistor now againg its not adjustable.
    What should i do now.i cant imagine the problem.
    Any suggestions?
    And im not using fine tuning now.only 5k pot as R1 and 470R resistor as R2.


    Reply 2 years ago

    LM2596 is feedback IC therfore I guess it should perform better but I haven't made any comparisons in practical so can't say for sure. Whereas it also depends upon the application if you are using it to power something that does not drain more current than 1A Lm78xx will do just fine. Moreover there are different versions of the same IC i.e. 2A version and so on. It all comes down to your application requirements.

    usbg3rdkavish laxkar

    Reply 3 years ago

    Go to File -> Import legacy project, a dialogue box will appear. In schematic file browse for *.dns File and in layout file browse for *.lyt File. then click Import.


    5 years ago on Introduction

    how do I view the .dsn schematic file.. I really want to build this and cant find the schematic for it

    2 replies

    Reply 5 years ago on Introduction

    Dear bro ,
    all the 3 files can be opened by Proteus 6.78SP2
    DSN contains the design (simulation)
    LYT contains the layout (for PCB making)
    and the SDF file is just conccections and is not used that much often
    Thanks :)


    7 years ago on Introduction

    i am interesting in your schematic,because it looks smaller than the most i have seen before
    may i ask for one?
    maixianyu@126.com thx

    1 reply

    Reply 7 years ago on Introduction

    I have already uploaded them in the instructable any how
    here is the link to the schematics


    and here is the link to pcb layout


    u can ask if u have any problem in this regard .thanks and rate if u like it : )


    7 years ago on Introduction

    what is the range of the FINE voltage tunning? I mean the voltage variation over the coarse voltage.

    I think you could add some protection for the regulators and the primary coil in the transformer (SCR, fuses,...). Adding some diodes as described in the LM317 datasheet is easy and protects better the regulator.

    Ah!, and a power ON LED :D

    2 replies

    Reply 7 years ago on Introduction

    there are two variable resistors (pots) one for varying the voltage from 0-12 and the other for fine tuning (+-0.3v)

    and i don't think adding the protection diodes will help because i m using a 800mA fuse
    as soon the current exceeds this limit it stops delivering output and the safe limit of IC (lm317) is 1A so the diodes are not nesecessory in this case. if u want 1A output then u may use them.

    LED is a gud idea but its mostly used for debuging purpose and draws current giving at least -0.3v change in output so if u r using it with generic sort of thing it might reset it .....
    but still in ordinary cases its fine thanks for visiting u can ask if u still have any query.
    and do tell me if u have any solution for the surge current :)


    Reply 7 years ago on Introduction

    I run my power indicator lamps right off the top of the filter capacitor, that way it doesn't draw on the regulated portion of the circuit, and it bleeds the charge off the cap. Plus I like how they fade when I turn my supplies off.

    Just how I like to do it here.