Do you really need 0 to 30v and up to 5A? Because the problem with linear regulators in wide-range variable voltage supplies (and to make things worse, high-current) is the power dissipation

describe the Switching method please

 

This website has all the design resources you need to build a switch mode power supply.

Read it. If you want to build this to learn, you need to start learning.

This page will explain the terms and methods for power supplies.

You need to read this to understand how they work and what is involved. It will answer your questions, and you will see what is involved in making a supply like you ask for.

http://smps.com/Knowledge/free.shtml

 

thanks retched
i read this site and than next questioning on SMPS

 

hello Riffo
where are you
please explain next thread

 

SMPS is out of ur league.
Did u understand constant current or not?

 

Did u understand constant current or not?

In CC current not vary with load but this is how possible
i am right or not


please next describe method how to build a PSU

 

Method:
Use a transformer to drop the mains voltage to just above the MAX voltage of the PSU you want to build.

Rectify the AC to DC.

Use filters to clean the supply as much as possible.

Use a variety of linear regulators with heatsinks to keep the power dissipation at reasonable levels.

Or

Using a switch mode, you will need a swithmode regulator or build a swithmode regulator capable of your requirements with in the particular parts specifications.
The All About Circuits eBook at the top of every page on this site will teach you what you need to know to understand the remaining pages.

smps.com has the information. I linked to that earler.

Googe.com for 'power supply circuits' gives many results.

The datasheet for each part will tell you what it is capable of.

You can also search the manufacturers websites for Application notes and design notes.

What more do you want? Are you asking us to do all the work for you?

All the info you are asking has already been told in your two threads.

If you are not understanding, you need to read the eBook and get a grasp on the terminalogy first. Then things will start to make sense.

You DO NOT need such a suppy to start an electronics hobby or education.

If you have a NON VARIABLE 30v 5a Power Supply, you can make voltage dividers and such to make that supply work with particular circuits. YOU DONT NEED such variability. Just look at your house. The outlets are NOT variable. And look what you can do with it. The circuit or experiment you build can handle the voltage change. The supply does not have to.

You would have already had a good supply and been creating if you would have built a 30v 5a supply.

 

Method:
Use a transformer to drop the mains voltage to just above the MAX voltage of the PSU you want to build.

Rectify the AC to DC.

Use filters to clean the supply as much as possible.

all the ok

Use a variety of linear regulators with heatsinks to keep the power dissipation at reasonable levels.

first i use with transformer power supply with regulator use
Lm317 but the problem is that this IC is max current 1.5A

Second 7805 7812 fix regulator use

third UA723 Ic That problem is 6 or 7-35V but i want 0-30V

Fourth i make using lm338 use but the problem is that max 1A lower than 8V while i design 0-5A current limiter use at 0-30V supply

fifth any idea other regulator whose cover 0-30V and 5A regulator

for regulating the regulator ic better or using transistor and comparator IC use better

i seen that many companies (eg HP power supply) using transistor regulator

If you are not understanding, you need to read the eBook and get a grasp on the terminalogy first. Then things will start to make sense.

what is e-book

You DO NOT need suck a suppy to start an electronics hobby or education.

for home use an electronics hobby

 

Umer.. you cannot draw 5Amps from 3 terminal regulator and have the voltage variable in such a huge range.
None of here is ready to provide assistance as you do not do what they tell you.
Will you atleast listen to people who is willing to help you

 

If you want to use lm338, you need to use 5 or 6 of them together in a circuit to get the 5a out of the circuit.

What you are not understanding, is the 1A is for 1 IC. If you use multiple, you add together the current it can handle.

If you look at schematics of higher current PSU, they use more than on LM338.

The eBook is the Electronics Book. All About Circuits is a BOOK. The is the forum for the book.

Here is the link to the book:
http://www.allaboutcircuits.com/vol_1/index.html

 

If you want to use lm338, you need to use 5 or 6 of them together in a circuit to get the 5a out of the circuit.

What you are not understanding, is the 1A is for 1 IC. If you use multiple, you add together the current it can handle.

If you look at schematics of higher current PSU, they use more than on LM338.

ok
in lm338 use 5 IC use for as current limiter and 5 ic use for voltage regultor that a very large circuit and expensive circuit

please any other circuit diagram send whose cover my requirement
please donot angry i serious for making power supply. in market a very little power supply can handle 0-30V and 5A these supply make usnig transister as regulator

i know that retched you are a very knowledgeable man na s this requirement is not problem for you
please solve my problem thanks

 

in lm338 use 5 IC use for as current limiter and 5 ic use for voltage regultor that a very large circuit and expensive circuit

please any other circuit diagram send whose cover my requirement
please donot angry i serious for making power supply. in market a very little power supply can handle 0-30V and 5A these supply make usnig transister as regulator

i know that retched you are a very knowledgeable man na s this requirement is not problem for you
please solve my problem thanks

This requirement IS a problem for me.

If you think 5 338 for current and 5 338 for voltage is too expensive and too complicated, you have to give up for now. There is NO way around a complicated circuit dealing with these temperatures and currents and voltages.

It isnt just attaching a few wires. You will need to buy chemicals and copper clad to make you own circuit boards, you will need to buy expensive heat sinks, and a fan, you will need to but a transformer capable of handling the current and voltages. You will need a complicated circuit for selecting between the 0v and 30v, and a display that will show you what voltage it is set to. I dont think you have any IDEA what your in for.
If you are building to save money, you are supremely WRONG. You need to buy all the equipment to build this first. Then the parts. Then the time.
You WILL pay twice the amount for a home built PSU than a store bought PSU.

$118us for EXACTLY what you want:
http://www.elexp.com/tst_3003.htm

They buy their parts in bulk and build 1000's at a time, thats why they are so inexpensive. Your will cost around $200us or more.

Now:

do you HAVE to use the LM338?

Do you have access to different ICs? If I gave you the help, are you going to say thanks for 15 posts, then say "Now how do I do this with a rock and some spit?"

This is not up for negotiation. When we say 'NO, IT WONT WORK" you cant keep telling us, "But the datasheet says 5a".

If you have not read books or taken classes in electronics, you DO NOT know how to read the information. We try to help you, and you act like you are taking the advice, but then you come back and say, ok now how about LM338?

Every time a new member posts in your thread, you start ALL over again. Asking, "I NEED A 0-30v 0-5A PSU made with a LM338 can you help me?"

The answer is NO. We have spent years learning and reading and failing. We have all already blew up LM338s ten years ago. So when we tell you why it wont work, you say ok thanks, and then ask the next person the same thing.

You dont listen to anything we say. If we tell you to be careful so you dont kill yourself with the 5 amps of burn your home down and kill your family, How do I know you will listen?

You may come back and say:
IT blew up..
Then we will say:
Did you build it EXACTLY like we said?

And you will say:

YES, except I only used 1 LM338 because somebody on another forum said it says it can in the datasheet.

So, when you ask for information, and we give you information that you dont want to hear, you just keep asking someone else.

That is what is making us loose patience with your project.

You are a STUDENT. You are using the FORUM as your TEACHER.

You must treat your teachers with respect. And the way your acting, is disrespectful.

We say no, and you ask someone else in the same thread. and they say no. and you continue.

SO, if you want help. I need to know a few things.

BEYOND FIRST, You WILL follow all safety protocols in dealing with electricity.

FIRST, are you going to LISTEN?

SECOND, what components (besides LM338) do you have access to?

THIRD, what is your budget? How much money do you have to spend on this power supply?

Reply with the requested information, then we can get started.

READ ALL THESE SAFTEY PAGES. Then post telling me if you understand them or need help on the safety information:
http://www.allaboutcircuits.com/vol_1/chpt_3/1.html
http://www.allaboutcircuits.com/vol_1/chpt_3/2.html
http://www.allaboutcircuits.com/vol_1/chpt_3/3.html
http://www.allaboutcircuits.com/vol_1/chpt_3/4.html
http://www.allaboutcircuits.com/vol_1/chpt_3/5.html
http://www.allaboutcircuits.com/vol_1/chpt_3/6.html
http://www.allaboutcircuits.com/vol_1/chpt_3/7.html
http://www.allaboutcircuits.com/vol_1/chpt_3/8.html
http://www.allaboutcircuits.com/vol_1/chpt_3/9.html
http://www.allaboutcircuits.com/vol_1/chpt_3/10.html

 

It isnt just attaching a few wires. You will need to buy chemicals and copper clad to make you own circuit boards, you will need to buy expensive heat sinks, and a fan, you will need to but a transformer capable of handling the current and voltages. You will need a complicated circuit for selecting between the 0v and 30v, and a display that will show you what voltage it is set to. I dont think you have any IDEA what your in for.

i buy heat sink
transformer
rectifires
filter
2xlm338 (1 for current limiter and 1 for voltage regulator)
adc 0831 for display voltage

If I gave you the help, are you going to say thanks for 15 posts, then say "Now how do I do this with a rock and some spit?"

no you are wrong i dont spit and rock

This is not up for negotiation. When we say 'NO, IT WONT WORK" you cant keep telling us, "But the datasheet says 5a".

i buy the lm338 because in datasheet Says "guranteed 5A regulation"

If you have not read books or taken classes in electronics, you DO NOT know how to read the information. We try to help you, and you act like you are taking the advice, but then you come back and say, ok now how about LM338?

i 3 year diploma holder in electronics
i read data sheet and i understand that lm338 5A regulator
in data sheet if vin-vout = 30V the max output current can handle 1A
mean
vin = 38 V thus 0-8V can handle 1A max
other
vin-vout less or equal 10V than 5-7A max
mean
38-28 = 10
28 or above voltage can handle 5 to 7A
i am right or not
in between these two stages 8 to 28V how many current handle = ?

So, when you ask for information, and we give you information that you dont want to hear, you just keep asking someone else.

That is what is making us loose patience with your project.

You are a STUDENT. You are using the FORUM as your TEACHER.

You must treat your teachers with respect. And the way your acting, is disrespectful.

We say no, and you ask someone else in the same thread. and they say no. and you continue.

i am student and you are my teacher please dontmind and i respect you
and next i shall work that you are asking me
please dont mind

FIRST, are you going to LISTEN?
[/QUOTE
Ok

SECOND, what components (besides LM338) do you have access to?

i want design a power supply that requirement you are know
problem is that the supply in market that is small supply whose cover complete requirement
i design that is small supply whose complete cover requirement
i buy rectifire and filter cct and trnasformer
i can help about regulator circuit

THIRD, what is your budget? How much money do you have to spend on this power supply?

electronic experiment is my hobby and for hobby dose not seen budget
but i think a small power supply whose cover requirement that in market small power supplies

 

Did you read the safety pages I linked to?

If so, we can get started.

 

yes
i read the safety pages

 

i buy the lm338 because in datasheet Says "guranteed 5A regulation"
i read data sheet and i understand that lm338 5A regulator
in data sheet if vin-vout = 30V the max output current can handle 1A
mean
vin = 38 V thus 0-8V can handle 1A max

You do not know how to read in English:
When the rating is Vin - Vout= 10V then with an input of 38VDC the output is 1A max when the output voltage is 0V to 30V. They do not say the typical output current with a high Vin - Vout so it might be only 100mA.

other
vin-vout less or equal 10V than 5-7A max
mean
38-28 = 10
28 or above voltage can handle 5 to 7A
i am right or not

No.
A typical device has an output of 8A when the Vin - Vout= 10V or less.
But you do not know if your device is typical or minimum.

in between these two stages 8 to 28V how many current handle = ?

Nobody knows. Measure one to see if the current reduction when the Vin - Vout is high is linear. It changes a little when the temperature changes.

 

retched ...if you want to lead then be my guest..
I did have some work for the OP to test his transformer capacity.

 

I didnt mean so step on your toes, Rifaa. Go right ahead.

 

You do not know how to read in English:
When the rating is Vin - Vout= 10V then with an input of 38VDC the output is 1A max when the output voltage is 0V to 30V. They do not say the typical output current with a high Vin - Vout so it might be only 100mA.

hello audioguru please explain this topic with exmples

 

It's OK....retched.. no harm done.. by all means.
We are here to help.
But the problem is OP is confused whom to ask...
He does not read the post properly so what can we do if he is too fast then us
and to make things worse he doesn't understand certain terms and is worse than me.
Takes too much time to grab the meaning and when he gets too confused he doesn't ask but instead looks for some one else. What he doesn't realize is that everyone reads his thread. He just don't get it.
How many times did I ask OP to tell me something and we can go on but he doesn't want that. All he wants is to do what he thinks of the data sheet says. even though he is misinterpreting the data. He does not take the real world variables into account. If any where the data says 5Amps, then it should give that, and does not want to know under what condition that it applies.
I really donno what to do with this guy.
When Sgt gave up, who the heck are we to pursue a lost cause.