Picture of Inexpensive Power Supply, Versions 1
it blew up (the rectivier)
and i dont want to repair it
the lm317 still works
i need the powersupply for my plasma speaker
i need 24 V 

Well it is so cheap that if you are handy (like me), it only will set you back 3 or 4 dollars for a nice case.

With a well stocked junk drawer, you could even make it for free.

Would you like to see what it is?  It is a low voltage, variable power supply.

V1 = from 1.5 to13 volts positive output
V2 = from 2 to 35 volts positive output

With Version 1 you cannot use the higher output because the fan can only hande 12 volts.

You can modify it to handle  the higher voltage, but I suggest you build Version 2 instead.
Version 2 starts in step 5.

Step 1: Bill of Material

Picture of Bill of Material

Parts List:

1 - LM317 (Texas Instruments has the smd in the free sample program, the same one I used.)
1 - 10K ohm variable resistor (potentiometer) (pot)
1 - diode bridge (rectifier) or 4 fast diodes .  Watch the polarity!  Follow the schematic exactly.
1 - electrolytic capacitor 63V, 100-300uF (it doesn't matter.) ( Watch the polarity.)
1 - small heatsink for the LM317
1 - small PC fan (12V)
1 - small piece of circuit board
2 - connectors (so you can screw your wires instead of alligator clipping them)
1 - transformer (I used one that has 3 wires and 2 outputs, 13.5V and 27V)
Note:  In order to use the full power, use a transformer that can handle at least 1A because the LM317 can deliver up to 1.5A.
1 - box
1 - line cord with plug
Various lengths of wire

1 - voltage display (mine is from an old radio control (rc) transmitter)
there is a litle problem

adj.-out resistance should be at least 220 ohms   so if you put your pot all the way up it will short adj.-out (0 ohms)  not realy good for the lm317
robot797 (author)  garrys newman5 years ago
ya i know
but mine still works

i did blow it when i powered a flyback transformer

so the next version has some sort of protection
mathman475 years ago
OK, I made some corrections.  Version 2 needs its own schematic though.  It needs to show how to place the LED, the switch, and the resistor for the LED.  Also, you really should include a fuse on the hot side of the line cord before the transformer.  Otherwise if something happens, you have a nice little fire starter.
robot797 (author)  mathman475 years ago
that would be smart (the fuse)

mine has a thermal fuse build in
For some reason I wasn't able to correct some of the embedded captions.  Maybe you can.  "connector" is misspelled every time (2 "n"s in the middle).  How do you like my update?  Where is the thermal fuse?
robot797 (author)  mathman475 years ago
the thermal fuse is imbeded inside the transformer

the label shows that it can take 135 degre's celcius

i will coorrect connector
mathman475 years ago
I always enjoy your I*, if only to try and figure out what you're saying.  I offer you encouragement - and safety!
robot797 (author)  mathman475 years ago
thank you

i am corecting a lot on my grammas mistakes latly

so i can be be understandeble for others.

but it will never be the best
I also offer my help, if you want.
robot797 (author)  mathman475 years ago
sure that would be nice

What I was thinking was to download your I*, make some corrections, then send it back to you to post.  I don't want any credit.  I just think you have a good I* and it needs to be understand.  Or, I could just send you the corrections to make on your own. My email: mathman at comcast dot net.  Understand how to make this into an address?  I'm doing it this way so the bots don't have such an easy chance.  Glad to help.
robot797 (author)  mathman475 years ago
collaborated you into the project
if i am correct you can now edit it

if not you will get it via e-mail
zholy5 years ago
I did something similar as well ... 2 days ago. When I finished my dinner (china food), I was left with one bow like yours ... so I decide to put the power supply for my Proxxon there ... and it fits exactly, like the box was made for it :) ... and it is water resist as well.

Good thinking :)