adjustable power supply question? Using a LM338?

so I'm building a power supply that will have multi power outputs, from surge protected 120,  36v 10a 24v 2.5a,  12v 3a  9v 1a, 12v 1a,  5v usb, and 12v cigarette lighter output. there is also an adjustable 1.25 to 32v  5 amp, the problem i'm having is no mater what set up I try, I never get more than 1.8 amps out of the LM338, I have an input of 36v 10a, I've tried several diagram , can anyone point me to a diagram that will actually allow a full 5amps to be pulled? I have the LM338 on a huge heat sink. 

Question by ihoppoet 8 years ago  |  last reply 8 years ago


Help me step down AC voltage without a transformer?

Hi again. Well, the title explains everything. The goal is to make a 65W power supply the simplest way. I have capacitors and diodes, and I'll desolder other components if necessary. Just, if someone can give me instructions and detailing a little bit. May be you can post some schematics or useful links. I've already created the circuit schematic but I would like to see yours first. I will post mine later but it doesn't include the values of the components and maybe it contains some errors. It was enough hard for me to draw it. I'm no professional afterall!

Question by junkrecycler 6 years ago  |  last reply 2 years ago


How to make a 1-1.5 volt voltage regulator at 15 amps?

Hi, I want to make a high current (15 or 16 amp) voltage regulator that outputs around 1 to 1.5 volts. Does anyone know how this could be done cheaply and easily? I've looked at the 15 amp schematic in the LM338 datasheet (http://www.ti.com/lit/ds/symlink/lm138.pdf  page 11), which uses 3 LM338s in parallel, but I'm pretty sure that takes the minimum output voltage to about 4v, way too much for me. I've looked at using 2n3055 transistor, but it seems like I'd need ridiculous heatsinking and probably fans to avoid thermalling out. I'm thinking of taking my power from an old PSU, 5 v rails, so not too much of a voltage drop, but it's hard to find stuff that can handle these kind of currents. I'm pretty much stumped right now, anyone got any ideas?

Topic by lolkent 7 years ago  |  last reply 7 years ago


ATX PSU to Work Bench PS - Adjustable Voltage and Current question

I am working on converting an old 600W ATX PSU to a bench power supply for me to use for some lab work.  Not everything that I will be plugging into it will have built in current limiting capabilities.  The guide/setup i found on here that I will most likely be following are:  https://www.instructables.com/id/DIY-PSU-into-Bench-Power-supply/  &  http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply The first link is how I would like mine to end up looking. My PSU is rated as: +3.3V @ 32A +5v @ 50A +12v @ 24A -12v @ 1A -5v @ .5A My end goal is to be able to control the voltage and current output from each binding post.  I will be hooking up a multimeter to this as well and am thinking that i could control what it monitors by some dipswitch setup or switching setup(as far as to which binding posts it's monitoring). I do understand that V = IR.  So keeping 5v but only wanting 3A, i would increase the resistance which is why at first i thought i could play a POT in the circuit.  However after seeing how the voltage regulation was hooked up, I am confused how to do so now since it was connected in the fashion i thought i would need to control the current.  (https://www.instructables.com/files/orig/F2D/LMFU/FYYNECNH/F2DLMFUFYYNECNH.jpg) I would probably use a LM338 since it would allow for more current but again, i would love to be able to have the full 50A available all at one shot but i don't think those IC's allow for that. I am extremely new to all of this and am still learning as well, so if i was able to communicate what i am looking to do correctly and you have a way of explaining it to me, a picture would be awesome if you have the time to create one. :D TYIA for any suggestions.

Topic by agentc0re 8 years ago  |  last reply 8 years ago