Just a suggestion, loose the 741. It is a good teaching tool, but there are much better out there. Even a LM324, or a LM358 (both are really dated op amps) have much better specs.


Also, you DO NOT want to power the op amp from the variable side, create a fixed stable voltage with a simple regulator or zener. The 741 would stop working anywhere from 15V - 9V, it doesn't even spec it's minimum voltage (probably because no two chips are the same).

 

But from the thread so far I think the op, farhan89, is way over his head.

I agree.

This sounds more like a bet or boast than a real project.

Either you need 0 - 30Volts at 20 amps or you don't

4- 20Volts at 10 amps is nothing like so

What do you really need?

Incidentally paralleling regulators like that usually leads to grief which is why it is unusual.

 

Hello,

You may use LM317 instead of LM338, I think it's available in TO-3 package which may have Ic= 15A or so.. You might not find it in T0-3 package, but it's not a problem.. For the negative side, use the same circuit with LM337 which is the negative complement of the LM317.
Another idea, you may use one LM317 (TO-220 is good) with 2N3055 NPN power transistor with base connected to the output of the LM317, collector to the dc supply source, and the emitter is the output. several 2N3055 could be connected in parallel for higher power. The PNP complement of 2N3055 is MJE2955, use it with LM337 as the connections of the positive side.

What do you think our well-versed fellows?

Regards,
Hazim

 

Hello,

You may use LM317 instead of LM338, I think it's available in TO-3 package which may have Ic= 15A or so..

Completely wrong. Maximum current output from an LM317 is 1.5A, and not for very long if it is dissipating much in the way of power.

You might not find it in T0-3 package, but it's not a problem.. For the negative side, use the same circuit with LM337 which is the negative complement of the LM317.

The LM337 is a rough negative equivalent of the positive LM317 regulator. However, it is also limited to 1.5A output

Another idea, you may use one LM317 (TO-220 is good) with 2N3055 NPN power transistor with base connected to the output of the LM317, collector to the dc supply source, and the emitter is the output. several 2N3055 could be connected in parallel for higher power. The PNP complement of 2N3055 is MJE2955, use it with LM337 as the connections of the positive side.

You're trying to make this sound much more simple than it is.

You're wrong.

 

I think that this discussions is going day by day longer,

Actually i am Doing ELectronics and when i make any ckt at home i don't have my self made power supply to check the ckt.

I want to make big power supply but i know it would cost me alot
I want a portable one to check my circuits!

Kindly anyone can give me any circuit diagram which can give +- 1.4v to +- 24V with at least 5 Amp current???


If yes than plz post here i will be very thankful

Waiting for ur replies

 

Completely wrong. Maximum current output from an LM317 is 1.5A, and not for very long if it is dissipating much in the way of power.

I'm talking here about a TO-3 package as you quoted and not the TO-220 which have a max. current of 1.5A..

The LM337 is a rough negative equivalent of the positive LM317 regulator. However, it is also limited to 1.5A output

Actually I don't know detailed information about the LM337. Also here I'm talking about a TO-3 package..

You're trying to make this sound much more simple than it is.

You're wrong.

I know this isn't a perfect power supply. My idea have some problems (e.g. it needs resistors at the emitters of the 2N3055s, maybe 5W 0.22Ω resistors are good...). What I suggested is a simple and workable way. What farhan needs is a simple power supply to build for general uses. I personally had the same need before, and I build one according to the way I said... and my power supply is working fine from more than a year...

Anyway my view comes out of the basic theory I have and of my experiments.. Also I appreciate your proficiency

Regards,
Hazim

 

I'm talking here about a TO-3 package as you quoted and not the TO-220 which have a max. current of 1.5A..

Here is a link to National Semiconductor's page for the LM117, which is the higher rated version of the LM317:
http://www.national.com/mpf/LM/LM117.html
Please note that the same datasheet is used for all versions of the LM117/LM317.
Please also note that the TO-3 package has a suffix of "K".
Please also note that the TO-3, TO-220, and TO-263 packages are all limited to 1.5A output. Other package designs have a lower current rating.

Actually I don't know detailed information about the LM337. Also here I'm talking about a TO-3 package..

It's your lucky day today.
Here is National Semiconductors' page for the LM137, which is the higher rated version of the LM337.
http://www.national.com/mpf/LM/LM137.html
Please note that the same limitations apply to this regulator.

I know this isn't a perfect power supply. My idea have some problems (e.g. it needs resistors at the emitters of the 2N3055s, maybe 5W 0.22Ω resistors are good...). What I suggested is a simple and workable way. What farhan needs is a simple power supply to build for general uses. I personally had the same need before, and I build one according to the way I said... and my power supply is working fine from more than a year...

OK, now you have mentioned the emitter resistors, which are critical to keep the current balanced between several of them.

 

You corrected some of my fault thoughts. You're right
farhan I found this one for you: http://www.elecfree.com/circuit/power-supply/supply-regulator-0-30v-5a-by-ic-723-2n3055-2part/
It's a 0-30V 5A simple power supply circuit.

Regards,
Hazim

 

An LM317 has a max rating of 1.5A.
An LM350 has a max rating of 3A.
An LM338 has a max rating of 5A.

They typically give more output current.
Read the datasheets because they reduce their max output current when they have more than 10V or 15V from in to out.

 

The base problem still remains though, where is the basic unregulated voltage coming from?

 

You corrected some of my fault thoughts. You're right
farhan I found this one for you: http://www.elecfree.com/circuit/power-supply/supply-regulator-0-30v-5a-by-ic-723-2n3055-2part/
It's a 0-30V 5A simple power supply circuit.

Regards,
Hazim

Thanks SO Much!
What about the -30 v?
How could i make to acheive to -30 v?
Do you have any circuit of +-15 v 5 Amp power supply??

I also want to fix digital meters with that ?

so is it possible??
If yes then can you guide me????

 

This is what i want :

But the max current through this circuit is very low, is there any way to increase the current??

If yes then how ?
Also i want to add a digital meter for both negative and positive voltage nodes so anyone can guide me about that???

 

You corrected some of my fault thoughts. You're right
farhan I found this one for you: http://www.elecfree.com/circuit/power-supply/supply-regulator-0-30v-5a-by-ic-723-2n3055-2part/
It's a 0-30V 5A simple power supply circuit.

Regards,
Hazim

This is a rather poor design.
Being a bench PSU, current limit is not implemented. A short will be disastrous
And the emmiter resistors, why the heck does it need two 5W's when one will do, even a 2W at 0.1Ω will suffice, since shared max current is 2.5Amps tops.

An overlooked circuit I'll say.
Go ahead OP, make it and you will suffer.

I wonder why no one looked into it when it was presented by this forum with such errors. We are better than this.
@ Hazim,
Did you test this supply, being the fact that you are suggesting it for the OP

 

Even My simulation failed.

 

Im scared to offer any help.. You want a portable power supply that supplies a whole lotta current, and you really dont have the knowledge to do this at all.. let alone safely.

Are you SURE of what you need? Are you sure you dont want to just buy one? Your medical bills or funeral will surely cost more than a power supply.

I think you need to do some soul searching and TRULY decide on what you are doing and what you NEED.

You have been all over the place in this thread. You have changed the values you want repeatedly, and you have gone from:

don't worry about the budget

in post 3 to:

So now it's easy or it would cost more?????

to post #25:

I want to make big power supply but i know it would cost me alot

The OP is not even mature enough to be honest.

I think we ALL need to go back to post #1, #2, and #3 and re-read then answer SIMPLY.

I want to make a 0-30v DC Power supply. I want separate pot for 0 to +30v and s separate pot for 0 to -30 V .

I also want high current in output approx 15-20 Amps

Is it possible ????

Regulated,
Linear or Switching ???
Can u define what is linear and what is switching ??

don't worry about the budget, but the transformer and the whole circuit should be installed in the 14*14 CM box

NO, its not possible unless its 5 feet tall and you are going to hurt yourself building it.

TO everyone else:

What are you guys doing? You have shut down threads for magnitudes less.
If you all want to get into a design match over who can build it, dont do it in this thread. Its going to get this OP, or another googler with the same experience level killed.

 

I think being a holiday and April fools day and all........
I wonder......

 

I've been waiting for our original poster to scale back their expectations to something more realistic.

Many hobbyist' projects power needs can be met by simply converting an ATX form factor PC power supply to a bench supply.

Googling "ATX bench supply" will produce thousands of hits, and lots of ideas.

This is a very inexpensive way to get a very useful bench supply in a hurry.
+/-12v
+/-5v
+3.3v
The negative voltages are low current (1.2A or less), but that is usually not much of an issue.

For the next project, they should build the simple 1A variable positive/negative supply that they posted most recently. That way they can become acquainted with the problems of power dissipation in the regulators.

Electronics has a long learning process. It is all too frequent that an ambitious newbie will take on a project that is much too complex for their existing skills. This frequently results in the project not reaching a successful conclusion, and the newbie becoming disappointed and disillusioned.

The more simple the project, the higher the probability of success. Successfully completing projects builds confidence in the person completing the project, along with the experience gained.

Even building a single 0v-30v 5A supply is a rather complex task for a newbie. It is difficult to make them understand how much power will need to be dissipated, and why it is that they will need a huge heat sink with fans and multiple output transistors.

 

I've been waiting for our original poster to scale back their expectations to something more realistic.

Many hobbyist' projects power needs can be met by simply converting an ATX form factor PC power supply to a bench supply.

Googling "ATX bench supply" will produce thousands of hits, and lots of ideas.

This is a very inexpensive way to get a very useful bench supply in a hurry.
+/-12v
+/-5v
+3.3v
The negative voltages are low current (1.2A or less), but that is usually not much of an issue.

For the next project, they should build the simple 1A variable positive/negative supply that they posted most recently. That way they can become acquainted with the problems of power dissipation in the regulators.

Electronics has a long learning process. It is all too frequent that an ambitious newbie will take on a project that is much too complex for their existing skills. This frequently results in the project not reaching a successful conclusion, and the newbie becoming disappointed and disillusioned.

The more simple the project, the higher the probability of success. Successfully completing projects builds confidence in the person completing the project, along with the experience gained.

Even building a single 0v-30v 5A supply is a rather complex task for a newbie. It is difficult to make them understand how much power will need to be dissipated, and why it is that they will need a huge heat sink with fans and multiple output transistors.

Thanks for the suggestion really appreciate it !
Have you check the ckt i gave in post No 32 of this thread???

It's very simple, i have tried using diffrent iC's and simulate it but it's giving max 1.2 mA

Can u suggest any IC that can regulate to 5 Amp ?
eve lm338 can regulate to 5 Amp but during simulation it's showing in mA.
So what to do???

 

Thanks for the suggestion really appreciate it !

You're welcome.

Have you check the ckt i gave in post No 32 of this thread???

I've glanced at it. It is lacking diodes across the regulators to protect against an accidental short at the input, but it's a fairly typical schematic.

It's very simple, i have tried using diffrent iC's and simulate it but it's giving max 1.2 mA

Then there is likely something wrong with your simulation.

Why don't you post your simulation? In graphic image format, please - .png format is preferred.

Can u suggest any IC that can regulate to 5 Amp ?
eve lm338 can regulate to 5 Amp but during simulation it's showing in mA.
So what to do???

This goes back to the power dissipation problem.

You want a 0v-30v supply that is capable of 5A.
If you took an LM138K (steel TO-3 case), with an input of 30v, current limited to 5A, and shorted it's output to ground, you would be dissipating 150 Watts in the regulator. 30v x 5A = 150W

The LM138K regulator has a thermal resistance of 1°C per Watt of power dissipated. It has a maximum temperature rating of 150°C.

This means that if you could freeze the regulator in a block of ice (0°C), and KEEP THE ICE FROZEN during the test, with 30v input, limited to 5A current and the output shorted to ground, the regulator would be right at the absolute maximum operating temperature limits. 1°C x 150W = 150°C

If you used the LM338T TO-220 case regulator instead, it has a thermal resistance of 4°C per Watt of power dissipated. It has a maximum temperature rating of 125°C.

If you froze the LM338T regulator in a block of ice and kept it frozen during the test, output shorted to ground, limited to 5A current, the maximum temperature specifications would be exceeded when the power dissipation in the regulator passed 31.25 Watts, which means when the input exceeded 6.25 Volts.
4°C x 31.25W = 125°C. 31.25W/5A = 6.25V.

Do you plan on keeping your power supply frozen in a block of ice?

Even that won't be enough.

 

You're welcome.


I've glanced at it. It is lacking diodes across the regulators to protect against an accidental short at the input, but it's a fairly typical schematic.


Then there is likely something wrong with your simulation.

Why don't you post your simulation? In graphic image format, please - .png format is preferred.



This goes back to the power dissipation problem.

You want a 0v-30v supply that is capable of 5A.
If you took an LM138K (steel TO-3 case), with an input of 30v, current limited to 5A, and shorted it's output to ground, you would be dissipating 150 Watts in the regulator. 30v x 5A = 150W

The LM138K regulator has a thermal resistance of 1°C per Watt of power dissipated. It has a maximum temperature rating of 150°C.

This means that if you could freeze the regulator in a block of ice (0°C), and KEEP THE ICE FROZEN during the test, with 30v input, limited to 5A current and the output shorted to ground, the regulator would be right at the absolute maximum operating temperature limits. 1°C x 150W = 150°C

If you used the LM338T TO-220 case regulator instead, it has a thermal resistance of 4°C per Watt of power dissipated. It has a maximum temperature rating of 125°C.

If you froze the LM338T regulator in a block of ice and kept it frozen during the test, output shorted to ground, limited to 5A current, the maximum temperature specifications would be exceeded when the power dissipation in the regulator passed 31.25 Watts, which means when the input exceeded 6.25 Volts.
4°C x 31.25W = 125°C. 31.25W/5A = 6.25V.

Do you plan on keeping your power supply frozen in a block of ice?

Even that won't be enough.

hmmm....

But i want to make +-15v power supply not 30 v ??

how much current could be drawn from my ckt?
lets not to talk of Current , so should i use the above ckt for +-15v or it's beeter if i made +-30v supply?
Need ur suggestion