0-30V Stabilized Power Supply

[audioguru2]

The biggest knob I found is 30mm in diameter. I'm wondering what would be better, this big knob or two potenciometers in series.

I find having a coarse control and a fine control is a nuisance. There is always one of the controls at its end but more adjustment is needed so a few adjustments on both controls is needed for one setting.
My power supply has a knob for voltage that is 40mm in diameter and I can set it to very fine settings.

 

[Hero999]

It's a matter of opinion.

I like using a 10 turn pot so I can have course and fine control with one pot but having to turn it ten times to go from one end of the range to the other might annoy some people.

 

[morpheous87]

I want to made a V-A multimer for the 30V PSU based on Aduino platform. So I have some questions about it. I need a voltage devider so  the maximum voltage be <5 and put it in analog Arduino's pin. But how this devider should look?
And for the current measurment I need a resistor to measure the voltage from both sides. Can the 82R resistor be used for this purpose (in PicMaster's version it's 2W resistor)?

 

[redwire]

morpheous87

Attached is an example of how to calculate your voltage divider.  Note that I added a potentiometer in the circuit so that once the program is written, you can calibrate it without have to reprogram the chip because of tolerance differences in resistors.

For the current measurement, if you already built the PS  all you need to do is measure the voltage drop across R7.  V=IR.  You know the resistor value, you measure the voltage drop with the ADC of your Arduino, then write code in your Arduino program to calculate and display I.

Note that your common ground for will be the transformer side of R7.

VoltageDivider.pdf

 

[morpheous87]

redwire
This is the pdf I used to build my PSU. I'm not sure that the R7 you're talking about is the R7 in the pdf. Could you check is there some differences. Note that part's names on the last pdf's page (mounting diagram) is different from the part list page. Thanks for the help!

EL_power_supply.pdf

 

[redwire]

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 (+).

 

[maciek1234]

hi, have any of you used any simulation software to check circuit behavior?,
could you ,please upload files from simulation here ,many thanks

 

[lighty]

Hi   Lighty     

Is this what you were thinking of making?

Yip, started something but have been caught at at work, need to spend some time on it.

 

[Riko1]

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?

Thanks in advance.

 

[audioguru2]

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..

 

[Riko1]

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.

 

[audioguru2]

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.

 

[Riko1]

audioguru, thank you very much for such detailed explanations.
Can you also tell me please does this power supply has protection against shorted circuits?

 

[audioguru2]

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.

 

[cblasiu]

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 .

 

[Tortax]

@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?

 

[audioguru2]

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

 

[morpheous87]

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?

 

[rajabi]

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

 

[audioguru2]

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.