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   :)
aclark321 year ago
how do I view the .dsn schematic file.. I really want to build this and cant find the schematic for it
usbg3rd (author)  aclark321 year ago
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 :)
thank you,
maixy3 years ago
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
usbg3rd (author)  maixy3 years ago
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 : )
gomibakou3 years ago
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

usbg3rd (author)  gomibakou3 years ago
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 :)
pfred2 usbg3rd3 years ago
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.
pfred23 years ago
Here is a dual voltage adjustable regulator board I put up on this site:


Pretty clean layout huh?