You can find a 1.2-30v 5A CV/CC supply in the datasheet for the LM117 in National.com site, at page 18. Take a look:

The LED should be red color. V+ in the LM301A should go to the output voltage, i think.
Since you already have the LM338, which is like a higher current LM317, i bet you can use it just fine.
All polarized capacitors are solid tantalum.

The MJ4502 has a thermal resistance junction-to-case of 0.88°C/W, and a maximum junction temperature of 200°C, but nobody goes higher than 150°C, and even that is very risky.

The heatsink you need must have a thermal resistance of:

\(\frac{TJmax - TAmax}{PDmax} - \frac{RthJC + RthCS}{numTransistors}\)​

TJmax is the maximum allowable junction temperature.
TAmax is the maximum allowable ambient temperature (for example: 35°C, if you want this to keep working at that ambient temperature).
PDmax is the maximum power dissipation, which in your case is 35v * 5A.
RthJC is the thermal resistance of the transistor's junction to it's own case.
RthCS is the thermal resistance between the transistor case and the heatsink, that varies depending on the thermal grease, mica, silpad, or whatever you're using between the transistor and heatsink.

Can you calculate the heatsink you need for one and two transistors, or whatever number of transistors is necessary?

By the way, paralleling transistors requires to add an emitter resistor for every transistor, in the order of 0.1 ohms. The power rating of the resistor would depend on the amount of current it's going tru them.

 

thanks Norfindel for helping me
can i discuss about this circuit

 

what is the meaning of attatch diagram highlight
lm317 is capable for 1.5A max
mj4502 is use for current increasing. use in parallel
1.5A in 317 and 3.5A in mj4502
i am ok or not
than next

 

Umer keep in mind that above diagram will not allow you to reduce the output voltage to 0V

 

lm317 is capable for 1.5A max

No.
Its output current is 1.5A only if vin - vout= 15V or less.
Its output current is 150ma to 400ma when its Vin - Vout= 40V.

mj4502 is use for current increasing. use in parallel
1.5A in 317 and 3.5A in mj4502

No.
The 33 ohm resistor allows the MJ4502 power transistor to conduct when the current in the LM317 is only 27mA, not 1.5A.
I think the 33 ohm resistor should be 3.3 ohms for a current in the LM317 of 270mA.

 

Umer keep in mind that above diagram will not allow you to reduce the output voltage to 0V

That's true, it would go to 1.2v minimum (that's the lower the LM317 can go with the voltage setting divider connected to gnd). You can make it go to 0v by connecting the voltage divider to -1.2v (there's a 1.2v voltage reference IC from National you can use).

Or, as you need -6v for the OPAMP anyways, you could connect it to -6v, if you add a trimmer between the voltage divider and the -6v, to keep the lowest ouput voltage at 0v, but be careful if you attempt this, as you can exceed the max voltage of the IC if you make a mistake.

Take a look at the application notes for the LM317. If you know about OPAMPs, you can learn how the regulator works, and understand what i just said better: http://www.national.com/mpf/LM/LM317.html#Documents

Anyways, it's really needed to go below 1.2v? The current limiting circuit will set the output to 0v if necessary, even if it cannot be set to 0v with the potentiometer.

 

Nice thread! Contributors keep posting and OP (from Pakistan, not from India) keeps getting nowhere.

In so many forums it happens the same: more nonsense posted more contributors trying to straighten up something that started wrong.

 

The 33 ohm resistor allows the MJ4502 power transistor to conduct when the current in the LM317 is only 27mA, not 1.5A.
I think the 33 ohm resistor should be 3.3 ohms for a current in the LM317 of 270mA.

Could be. It works anyways with the 33 ohm resistor, but they even used the TO-3 version, that is absolutely overkill even with 270mA. Maybe they're using it without heatsink?
However, current limit for the LM317 can kick as low as 0.15A with Vin-Vout = 40v, which is probably why they chosen such a big resistor.

Umer: if you make the heat dissipation calculations i wrote, you will find it's nearly impossible to use only one transistor.

 

very very thanks norfindel
Audioguru

1. V = 0.7V & R = 33Ω than I = 21mA when 21mA going thru 33Ω transitor go on and current going thru transistor

it mean the current thru lm317 is 21mA and heat sink not neccessary

2. R2 is 0.4W resistor

Or, as you need -6v for the OPAMP anyways, you could connect it to -6v, if you add a trimmer between the voltage divider and the -6v, to keep the lowest ouput voltage at 0v, but be careful if you attempt this, as you can exceed the max voltage of the IC if you make a mistake.

please expalin with diagram

3. Please explain how this Op Amp work and how current control i think this op amp use for current limitimg

4. current limiting 0-5A or not

5. the external supply is use for op amp how many +ve supply at Pin 7 of IC

6. what is value of R8

7. what is Equivalent of the diode 1N457

8. is op amp 741 is Equivalent of lm301A or not

Umer: if you make the heat dissipation calculations i wrote, you will find it's nearly impossible to use only one transistor.

The heatsink you need must have a thermal resistance of:

for transister

TJmax = 150 °C
TAmax = 35°C
PDmax = 150W
RthJC = 0.88°C/W
RthCS = ? if i use silicon compound than = ?
numTransister = number of transistor

150-35/150 - 0.88+?/1
0.766 - ?
area of heat sink
this formula is for aluminium or other

thanks norfindal
&
audioguru
please explain this thread

 

so many members suggesting so many methods will confuse the OP.
Lets decide one thing. Decide who to lead this project. then from here no one should suggest additional methods, as the OP tends to change his mind during mid way of project.
This will help in getting this done much faster and avoid confusion

 

I think you must have forgotten we tried to tell the OP that his requested way would not work.

So we offered another, then he would shoot it down because something he read incorrectly in a datasheet or another forum.

Then someone else offerers insight, and it is again shot down by the OP.

He probably has 2 LM338s sitting around and that is all. He want them to work.

He has not been willing to take an offer for other ICs.

This thread is not a result of overzealous people trying to help.

This thread is a result of an OP that does not want the help he is getting.

So, the many people keep trying to get the OP to realize the shortcomings of the ICs he wants to use, and need him to choose one of the methods that will work.

 

So OP decide one and stick with it.

 

But he cannot get an LM301A opamp and doesn't know how to read datasheets to see that a 741 opamp is a completely different animal from the LM301A.

 

what ever the case, members make a suggestion.
If He wants me to help then he has to follow my supply design, I can simplify it to his needs.
That is my offer.

 

He DOESN'T want any help thats does NOT involve using the 2 parts he has said he wants to use 300 times.

Umer_Farooq wrote:
Please help me for electronics knowledge i am a new student in electronics and i first project
thanks

Umer, why not start out by building a 30v supply just to learn how things work and what does what?

That way, once you get some understanding, and experience, you can continue.

If you want, you can re-use the parts.

This way, you are getting knowledge, and can start making projects.

You can learn how to use voltage dividers and other methods to get the different voltages out of your 30v supply.

Once you realize that, you can start using other parts and understand TRULY what datasheets show and how to read them.

You could of had this built weeks ago instead of running in circles.

Think of it this way:
You want a car to get to work
You say, "I want a Ferrari."

You have $500 and you cant get the Ferrari, but you can get used Buick that will get you to work so you can make more money to achieve your goal.
Because now, you have nothing, and if you dont take the first step, you will stand still. You could at least have something to get you moving.

If you think you cant get 12v or 28v or 24v out of your 30v powersupply, you are wrong. If this is the case, you have a lot to learn. And this learning can start by building this first supply.

If you have the LM338s, build one of the schematics on the datasheet to get started.

You can always pull it apart and make it variable as you acquire heatsinks and more regulators and most importantly, more experience.

 

But he cannot get an LM301A opamp and doesn't know how to read datasheets to see that a 741 opamp is a completely different animal from the LM301A.

dont worry friend
i fresh diploma in electronics and in electronics not long experience
i read data sheet lm301A op amp they differ from 741
lm301A is basically comparator ok dont worry friend
OK

So we offered another, then he would shoot it down because something he read incorrectly in a datasheet or another forum.

i canot read data sheet first .now i read data sheet they can differ from 741
ok

This thread is not a result of overzealous people trying to help.

no you injured my heart
i really designed but many people in this thread one tell other types and other tells other types but i choose this that can send norfindel and i questioning for electronic knowledge gain
please answer my questions
and donot worry
i serious for designing


All to thanks

 

Still you haven't decided what to use?
Decide that and stop thanking and thanking instead make an effort on deciding what you want on what you and what you are willing to buy and stick with it.

 

very very thanks norfindel
Audioguru

You're welcome.

1. V = 0.7V & R = 33Ω than I = 21mA when 21mA going thru 33Ω transitor go on and current going thru transistor

it mean the current thru lm317 is 21mA and heat sink not neccessary

Well, that's pretty close, but is a little more complex. The on voltage at 5A is higher than 0.7v, it can reach about 1v, so the on current can reach 30mA on R1. The regulator current is going to be this current and the transistor's base current Ib, that is going to be about Ic/hFE.
The formula is shown in the page 13 of the LM340 datasheet. But i think you should read all the allaboutcircuits e-book (http://www.allaboutcircuits.com/vol_1/index.html) to refresh your knowledge before jumping in this kind of stuff.
Retched's suggestion is a good one: start by building a standard variable voltage supply with your LM338's. Start with the basics.
I'm electronics technician, and i readed it all, and even occasionally take a look at it. If you want to learn, that will be the less painfull way.

please expalin with diagram

You can understand that, by reading the application notes for the LM317, and understanding how the IC works.
Sorry, but i cannot teach you OPAMPs here, you will need to read the e-book for that, or buy some book on the subject.

5. the external supply is use for op amp how many +ve supply at Pin 7 of IC

I think you can connect that to Vout, or a fixed 30v supply.

6. what is value of R8

That's the voltage set resistor for the LM317. You can see the formula on the LM317 datasheet, or better yet, learn why the formula is like that, by reading the application notes. "3 terminal regulator is adjustable" is a good one.
If you want to learn, that's the path to go. If you just want to build the supply, i would suggest you to buy one.
Commercial supplies either have a switching pre-regulator, or have multiple connections in secondary, and relays are used to select the closest input voltage for the regulator to run at reasonable power dissipation.
It would be cheaper to buy the commercial supply, really, as the electricity bill will go up with a supply that is dissipating 35v*5a=175 watts.

7. what is Equivalent of the diode 1N457

I have no idea, why wouldn't you just buy the 1n457?

8. is op amp 741 is Equivalent of lm301A or not

Nope, they're different.

for transister

TJmax = 150 °C
TAmax = 35°C
PDmax = 150W
RthJC = 0.88°C/W
RthCS = ? if i use silicon compound than = ?
numTransister = number of transistor

150-35/150 - 0.88+?/1
0.766 - ?
area of heat sink
this formula is for aluminium or other

Worst case power disipation for the transistor is about Vce * Ic. As the input voltage is 35v, it's going to be 35v * 5A = 175 watts. For the thermal interface, you can guess about 1°C/W, but you can get the precise values from the manufacturer of the interface material.
The result is in °C/W. It's the thermal resistance of the heatsink you need.
If you get a negative value, it means that no heatsink will keep the junction temperature below TJmax at the ambient temperature you chosen with that amount of transistors.

 

i attatch the diagrm i assembled this circuit on bread board and see result these switches control with counter. resistor value are taken 1,2,4,8,...etc step this power supply is designed in digital mode
i design this power supply on PCB
but the problem is 1A max

 

next i desined this circuit that send norfindel