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adjustable power supply question? Using a LM338? Answered


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. 


6 Replies

user
seandogue (author)2010-07-03

If the heatsink is really working properly and it's not suffering from thermal effects, it could be resistive losses in your feedback loop.

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ihoppoet (author)seandogue2010-07-08

do you know where I can get a good etch schematic for this, I've been trying everything I can think of, I found one and tryed it, power doesn't even make it through, i'm pretty new at this, but i have to get this power supply up and running before i can go any further on my project. i would be grateful for any help you could give.

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seandogue (author)ihoppoet2010-07-08

A PCB layout? No, I can't say that I can.  I do not have such a pre made PCB layout available to share with this community, and I'm tasked with professional work that limits my participation in this forum to moderately simple answers, which themselves may require a certain amount of technical familiarity on the part of the reader. I apologize if that doesn't meet your needs.

You may be able to find a PCB layout on the net. If it were me, I'd google it. Other that, sorry I'm afraid I can't offer you any further help.

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NachoMahma (author)2010-07-03

. http://diyaudioprojects.com/Technical/Voltage-Regulator/ Scroll down to current calculator

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ihoppoet (author)NachoMahma2010-07-03

do you know how to calculate the loss on an adjustable set up? I'm using a 5k pot

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NachoMahma (author)ihoppoet2010-07-04

. All I know about 338's is what I can Google

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