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0-30V Stabilized Power Supply


redwire
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Hello Sirs,
I would like to make this power supply too. I got 420W transformer.
It is possible to connect 2 psu to 1 transformer?

The transformer's voltage is also important.

Why do you want 2 psu's? You will not be able to connect then in series and will not be able to connect them in parallel. You will not have a positie psu and a negative psu which is possible with 2 transformers or with 2 windings on 1 very powerful transformer..
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I'm sorry Sir, forgot to mention, that transformer is 2 windings 2x30V. If I will make two channels psu,  wouldn't be awaste of this powerful transformer. But why I can't  connect two psu in seriers or parallel?
Do I need 2 separate transformers for this task?

Thanks in advance.

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Thank you for telling us the very important details of your transformer.
Since it has two 30VAC windings then it can power two of the circuits.
You can connect them in series to get up to 60V or have one as a positive supply and the other can be a negative supply.
The regulated supplies use negative feedback so they cannot be connected in parallel.

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The original project has many problems, is not reliable and does not work properly.
The revised project works perfectly and is reliable.

It has adjustable voltage regulation and adjustable current regulation. It you short the output at any setting then it smiles and simply gets warm.

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Hello guys. I just finished the supply. I used the original project with uA741 op amp instead of tl081. It worked at fist start :). I must tell you all, that I'm almost 0 in electronics so please be gentle with me. I build this supply because I like very much led-s and and every time when I build something I use 6 or 12v battery and, because Murphy is alive ;D , they are discharged when you need them more. I put a led voltmeter( 20V range because I don't use more then 14 volts) and I want to put a led ampermeter but I don't now how. I put it in series with  minus but it show the current absorbed by the project I make and I want to show me the value set for the current limitation. I thank you in advance for your tips and soon I will put some pictures .

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@cblasiu: You can do this by short circuiting the + and - terminals of your power supply, while in short circuit the value shown on your display will be the current limitation value of the power supply itself.

Hi all,
This tread is now 68 pages long and sadly enough I don't have time to read them all right now.
Can anyone tell me @ witch page I can find the latest revised schematic?

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morpheous87

Well yes and no.   I am refering to  the 0.47Ohm resistor that is connected to TB4.   I say this with a little hesitation because on the Bill of Materials, R7 is listed as a 3k9 resistor which I believe is an error.   The pcb shows R7 as being connected to the led (I think this should be R22) ,   and the sketch describes the shunt resistor as R7, 0.47 Ohms connected off board via TB4 which looks right.      

  The common ground is  (for Ardunio)  pin 2  on TB4.   To measure current, you measure the voltage drop across TB4.

   To measure voltage output connect to Pin 2 on TB4(-) and  TB3 (+).






I have a question about Arduino and PSU connections. In way I use pin2 on TB4 for common ground, how could I measure the voltage drop across TB4 ( it's on the groung signal path). I measured the voltage drop with common + and the two sides on the TB4, but I measured it with a multimer, with Arduino I need common ground. So I think the shunt resistor should be on the + ouput?
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Hi friends:
Thank so mach for your powerful site
I build this power supply http://www.electronics-lab.com/projects/power/001/index.html
so I try to upgrade the amps of it so I change the 2N3055 to two BUX98 Transistor and parallel them as you know it need to put a small and big resistance in emitter of those transistor so I put 0.27 ohm 5W for each of them and change input bridge diodes to 35A bridge but when I take just 1 amps continuously the heat-sink getting hot.
I know I am never good designer so I need strongly your help to fix my problem, can you arrange your project for my two BUX98 Transistor and I must told you I check this power supply circuit with 5A adjustable transformer that I put it to 24V as your circuit is needed but I have 35V 5A Transformer that can give us 5A continuously.
Can you arrange your circuit with this Transformer too.
sorry for every things

Best Regards

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The original project has many errors so it does not work properly and it is not reliable. therefore we fixed it in this thread and in another thread in the forum.

If the positive unregulated supply from your 24V transformer is 32VDC and the output to the load is 5V then the output transistors have 27V across them. If the load current is 1A then each of your two output transistors dissipates 13W so they will need a pretty big finned heatsink to get rid of that much heat.

The 24V transformer voltage is too high for the opamps in the original project. The 35V transformer is also too high for the opamps in our fixed circuit.

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The original project has many errors so it does not work properly and it is not reliable. therefore we fixed it in this thread and in another thread in the forum.

If the positive unregulated supply from your 24V transformer is 32VDC and the output to the load is 5V then the output transistors have 27V across them. If the load current is 1A then each of your two output transistors dissipates 13W so they will need a pretty big finned heatsink to get rid of that much heat.

The 24V transformer voltage is too high for the opamps in the original project. The 35V transformer is also too high for the opamps in our fixed circuit.




Thank you a lot for your answer
It is so difficult for me to find the final version of your project in this thread and in another thread in the forum because my English is too weak and it take so mach time therefor if it is possible give me the final version of circuit or link me in to it.
about the 35V transformer can I use some Zener diode for limit op amps IC to solve the problem and how can I do it

best regards
thanks again for your kind attention and corporation
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It is so difficult for me to find the final version of your project in this thread

The latest schematic and parts list is on page 55 of this thread.

about the 35V transformer can I use some Zener diode for limit op amps IC to solve the problem and how can I do it

Then the output transistors must dissipate a maximum of 49W more heat than with a 28V transformer.
The driver transistor will also get too hot.
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morpheous87 ,

Arduino ground is  TB4 pin 2

Connect the Arduino's ADC pin  to TB4 Pin 1 on your power supply.    Note that you are simply measuring the voltage drop across the 0.47 ohm resistor.  If you had a 3 amp load on the PS then your voltage drop across the resistor would be 0.47x3 = 1.41 V.    You should be able to measure this with your multimeter. 

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  • 2 weeks later...


The latest schematic and parts list is on page 55 of this thread.


Then the output transistors must dissipate a maximum of 49W more heat than with a 28V transformer.
The driver transistor will also get too hot.


hello
thanks a lot for your answer as soon as possible but I can not found the op-amp IC you mention in your new circuit. Do you know any other IC's that I can put in the new circuit?

About the 35V Transformer except of 28V Transformer it is Important for me because I most pay money again for new transformer and it is a little bit difficult...

Best Regards
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The two opamps selected for the modified and fixed project are made by two of the largest semiconductor manufacturers in the world.
The MC34071 is made by Motorola/ON Semi/ Freescale Semi and the TLE2141 is made by Texas Instruments. You can choose which of these opamps to use.

In North America and Europe they are available at hundreds of semiconductor distributors and in 30 to 50 countries at Farnell.

You don't say your country. Did you look to see if Farnell has an office/warehouse there?

Your 35V transformer is wrong for this project.

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Hi guys!
I have recently built the supply, but I have two major problems: Firstly I could set the upper limit of the voltage to 30 V, but the lower limit stays at 5.6V no mater what I do, and at this voltage the LED is on, and if I switch to the max current limit, then the voltage jumps from 5.6 to 12V. The second problem is that the voltage regulator pot is a 10k heli pot, and at the half way the voltage is at max, and furthermore I can't raise the upper limit.
The supply itself works great at higher voltages then 5.6V, so I can't figure out what is wrong.
Any help would be appreciated.

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Hi guys!
I have recently built the supply, but I have two major problems

Which version did you make? The original one with TL081 opamps? The first modification with OPA445 opamps? The latest modification with MC34071 or TLE2141 opamps?

What is the voltage of the negative supply at pin 4 of U3?
Did you connect the voltage-setting pot correctly? What is a "heli" pot? Its input is the 11.2V reference made by U1 and its output goes from 0V to 11.2V. It feeds the output amplifier that has a gain of 2.68.
The output of the project should be 0V when the voltage setting pot is minimum and should be 30.0V when the pot is at maximum. When the pot is halfway is output should be 5.6V and the output of the project should be 15V.

The current regulation should not do anything until the output current exceeds the setting of the current-setting pot, then it should turn on the LED as a warning that it is reducing the output voltage to limit the output current. 
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  • 2 weeks later...

First of all sorry for my english... I'm from Brazil and here power supplyes are too expensive for my pocket :)

I found in page 55 the new schematic and I want to build one for me. I have here a 25-0-25 5A transformer, so I belive it can get a DC voltage of about 50V

I think it can't handle the 0-30V 5A modification (or can??), but is it OK to make de 3A version?? Do I need to make any modification to use my transformer to this application?

Thank's

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Hi again!
The supply is the latest version with mc34071. The voltage at U3's pin4 is -1.5V. In my region, we call heli pot a potentiometer with multiple turns(12 turns for me).

With the voltage-setting pot at zero, the current setting pot at maximum and no load, measure the output voltage of each opamp and measure the output voltage of the project and report them here.
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First of all sorry for my english... I'm from Brazil and here power supplyes are too expensive for my pocket :)

I found in page 55 the new schematic and I want to build one for me. I have here a 25-0-25 5A transformer, so I belive it can get a DC voltage of about 50V

I think it can't handle the 0-30V 5A modification (or can??), but is it OK to make de 3A version?? Do I need to make any modification to use my transformer to this application?

The voltage from your transformer is much too high and will blow up most parts. It is 50VAC which makes 68.7VDC. If you use it as a 25V transformer then its voltage is too low but it could allow the project to have a max output of about 26VDC at 3.5A.
The minimum transformer voltage for the latest version of this project is 28V and the maximum voltage is 30V.
The current from the transformer will be 4.2A when the project has a 3ADC load and the transformer's current will be 7.1A when the project's output is 5ADC.
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