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0-30V Stabilized Power Supply

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Here you are an image of the schematic and the circuit itself (zip compressed - not .sch format allowed to be posted in this forum) corrected to be compatible with version 6.3 of Cadsoft Eagle

Why not post the schematic as an ordinary PNG file?.


Because the Eagle file can be useful to somebody else.

post-49877-14279144498589_thumb.png

Placa_principal.zip

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Hi Friends,

I am new to this forum, I want design a 0-30v power supply circuit which is given in this web site but i could not find few components in the market. Can any one please help me with replacement  of those components or otherwise an updated circuit.

Thanks in advance,
Ramu

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I want to build a 0-30v power supply circuit which is given in this web site but i could not find few components in the market. Can any one please help me with replacement  of those components or otherwise an updated circuit.

The circuit is already updated in the forum but not in the project. It uses parts that are common in North America, Europe and Australia.
Go to www.farnell.com and click on the flag of your country. They have warehouses of electronic parts all over the world.

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Hello to all,

I started building this power supply using the project on this web page http://diyfan.blogspot.com.br/2012/02/adjustable-lab-power-supply.html, which is basically the same project at this listed here. But I have a couple of questions.

First, from the posts I have read here, I saw that the recommendation is to use the MC34071APG IC. I managed to get a hold of MC34071PG IC (difference between these two is the lower input offset voltage of the MC34071APG). My question is, can I use this MC34071PG IC for this project?

Secondly, the transformer used in the project has one primary and  two secondary windings, one secondary providing 30VAC at 4Amps, but I have the problem in determining the characteristic on the second secondary winding (I guess that I need at least 9VAC for providing the power to the temperature controlled fan and panel ammeter)?

Thanks in advance :)

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First, from the posts I have read here, I saw that the recommendation is to use the MC34071APG IC. I managed to get a hold of MC34071PG IC (difference between these two is the lower input offset voltage of the MC34071APG). My question is, can I use this MC34071PG IC for this project?

I never recommended using the "A" version of the opamp and I don't remember if anybody else did.
The difference is so small that you will not notice the difference.

Secondly, the transformer used in the project has one primary and  two secondary windings, one secondary providing 30VAC at 4Amps, but I have the problem in determining the characteristic on the second secondary winding (I guess that I need at least 9VAC for providing the power to the temperature controlled fan and panel ammeter)?

Instead of ordering an expensive custom-made transformer with 2 windings, simply use 2 ordinary transformers.

This copy of my improvements uses only a single 2N3055 output transistor that will get extremely hot. My version uses two 2N3055 transistors, each with a 0.33 ohm emitter resistor. Then both transistors share the heat.

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Thanks audioguru on the answer :).

Yes you are right, my mistake, no one recommended the A version of the opamp.

I will use this MC34071PG opamp that I have.

Thanks for the suggestion to use two 2N3055 transistor to share the heat. I will use that modification.

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Hello everybody!
I wanted to build the first version of "0-30VDC Stabilized Power Supply with Current Control 0.002-3 A"
But now I saw this topic,and I have a few questions.
I tried to read this topic,but there is 100 pages, so i think that is better to ask.
I saw,that there are more versions of this PSU,but i don't have new transformer with 28-30V and 3+ A.
Can anyone help me,I'm new to this things.I don't want anybody to do my homework and if I must i will read the whole 100 pages if there are answers to my q.
My transformer is rated to 25.5VAC,3.6A.
My question is, will this version work with my transformer?
index.php?action=dlattach;topic=19066.0;

and this parts

index.php?action=dlattach;topic=19066.0;

if not, can anybody help me,to make changes to get this working.
I don't need for this PSU to give me 4+ Amp,just to give me 0-30VDC and 0.002-3A (3.6A)
Thanks in advance!

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My transformer is rated to 25.5VAC,3.6A.
My question is, will this version work with my transformer?

I don't need for this PSU to give me 4+ Amp, just to give me 0-30VDC and 0.002-3A (3.6A)

Your transformer is rated for (25.5V x 3.6A)= 91.8VA.
The circuit works from rectified AC and the peak voltage is (25.5V x root of 2)= 36V. Then the transformer is overloaded if the output DC current from the project is (91.8VA/36V)= 2.55A.

The rectifier bridge reduces the output 2V and ripple reduces it further maybe 2V. The current-sensing resistor R7 reduces it (2.55A x 0.47 ohms)= 1.2V. The output transistors reduce it about 1.5V and the driver transistor reduces it about 0.8V. The saturation voltage of opamp U2 reduces it about 1.8V. Then the total reductions are 9.3V so the maximum output voltage at 2.55A will be about (36V - 9.3V)= 26.7V and will be less if your mains voltage drops.

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Thank you very much  :D
So, if i understood right,it will work,but the maximum output of PSU would be 26.7V; 2.55Amps, without any damage to transformer or components..For my needs its good..
Anyhow i don't want to push it,but just one more thing,is there any way to modify PSU to give 30V?
It doesn't mater how many amps will give,i need the voltage.

Actually don't bother,if it will work,I will buy a new transformer one day.

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Hi raresvintea,  It appears that you used the original design that has several parts that need to be upgraded.  Papuga posted the most recent sketch and parts list two or three threads above your post. 

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With the original design, using a lower voltage transformer (i will not obtain 30V but who cares!!!), i want to pus BD139, what modifications i need to do? What is the scope of Q1 in the original schematic? If i put BD139 and keep TL081, did i need to do modifications? What are those?

The recomanded opamps in the newer version is expensive in comparasion with TL081!

If i understand well, for 5A, i need 4 output transistors to keep up with the current, and a better rectfier!

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I want to build this power supply. However, I am very confused about and how to start. There are several versions and proposed upgrades that I did not know what to do. I need the schematics and drawings of printed circuit board. The user "red baron" published schematics and pcb's desings, someone could confirm me if this is reliable? Apologies for repeating questions, I read a lot of stuff before, but I did not have my doubts resolved. Thank you.

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raresvintea,  check out http://www.electronics-lab.com/forum/index.php?topic=7317.msg1009204#msg1009204 or search for "inversion"  it will answer your questions about the Q1 and TL081.

I don't understand the concern that the new op-amps cost more.  They are about $1 more ($3 total) for the project.  The cost of boosting the power supply to 5 amps is probably at least $25 (beefier transformer, more 2N3055's, heat sinks etc).  Just building the original design and puting it in a case  is likely to run $80, so $3 more is insignificant.

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i'm currently building the 5A version. i have all the components soldered already on the PCB. however just now i noticed that D10 is not in the schematic but it's on the part's list. i have check again the final schematic from red and audio and both has NO D10 but it's on their part's list.

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The original schematic had a useless D10 from the base of the driver transistor to the output.
I deleted it from my schematic but it is still on the parts list by mistake.
The 10V/1W zener diode is on my latest 3A schematic (March 11/09) but it does not have a "D" number. It is D12 on my latest 3A parts list.

I didn't make a schematic for the 5A version because the changes are only a few.

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Audioguru,  Also note that the 10V, 1W Zener is listed as D12 on the parts list but on the schematic D12 is an led indicator for the current control.  If you make the changes I'll  post the revised parts list on the first thread.

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Hi AudioGuru
Finally the project is near completion - pics attached.  Thank you for the help getting to this stage.
I have two problems:
1) The current limiting circuit does not function correctly and I need some help with trouble shooting.  With P2 turned down to about 1kohm (near minimum) the LED comes on, but turns off one current limit is set higher.  Setting the maximums of 5A and 30V, the LED starts to turn on faintly and then gets brighter, but only at the max.  In between all works well.  Could Q3 have blown?
2) From the pics you will see that I have used Picmaster pcb, but I believe there is one mistake - the polarity of C10 (in your circuit C3) has the +ve on the pcb away from ground and -ve connected to ground.  Surely not correct?
Regards

post-83831-14279144502224_thumb.jpg

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