0-30 Vdc Stabilized Power Supply

[audioguru2]

This thread and a few other threads show the latest parts list and schematic. Some threads show a pcb layout.
Here are the details again.

Most of us learned electronics in high school and university.
A good book (I got mine on the internet for free) is The Art Of Electronics.

View attachment 41943

View attachment 41944

 

[ahmad.e.c.m]

hello everyone !!
I need a circuit which I can increase or decrease the current.
thanks

 

[audioguru2]

hello everyone !!
I need a circuit which I can increase or decrease the current.

Control potentiometer P2 increases or decreases the current in this circuit.

Ohm's Law says that in a certain resistance, increasing the voltage across the resistor increases the current and decreasing the voltage across it decreases the current.
That is how the current regulation in this project works. It senses the load current in R7 and opamp U3 adjusts the output voltage so that the load current is what you want. 

 

[ahmad.e.c.m]

Is there a circuit that can do the job alone?
thanks

 

[audioguru2]

Is there a circuit that can do the job alone?

A very large variable resistor and a power supply can increase or decrease the current.

Usually people change the voltage, not the current because the voltage and the load resistance determine the current.
Why do you want to change the current instead of changing the voltage?

 

[ahmad.e.c.m]

I really want to control the output current.
I would avoid the surge current.
Do you have a method?

Thank you for your help

 

[audioguru2]

I really want to control the output current.
I would avoid the surge current.
Do you have a method?

Ohm's Law usually controls the current. A low load resistance uses a high current. A high load resistance uses a low current.

When you change the current yourself then you are also changing the voltage.

This project regulates the current so you can set a certain maximum amount of current.

 

[ahmad.e.c.m]

My purpose is to control the output current.
For when the output is short circuit.
Like most power supplies.

 

[audioguru2]

This project has a current control pot, P2:
1) When it is set to minimum then the maximum current into a resistance or into a short is a few mA.
2) When it is set to maximum rotation then the maximum current is 3.0A.
3) When it is set to half rotation then the maximum current is 1.5A.
4) When it is set to any other amount of rotation then the maximum current will be the percentage.

If you set the voltage to 30V, set the current to 2A and the load is 10 ohms then the current regulator circuit reduces the output voltage to 20.0V because Ohm's Law says that 2A x 10 ohms= 20V. 

 

[pete1990]

hey,

first up thanks for sharing that project. I just recently build up my second version of the circuit, due to a failure of my first one (which wasn't looking too nice anyways...). And here is the reason why I'm writing here:
The Power Supply is almost working perfect, but there is a thing what I can't explain to myself. The regulation of voltage works fine. The regulation of current works as well, but if I turn the current pot all the way left (minimal current) the current limiter LED turns on (although there is no load at all connected). It doesn't matter in what positions both Pots are, my selfmade Volt and Currentmeter measures a small current from less than 10mA. That current is mesured and calculated over the voltage over R5. If I measure the Voltage over R5 with my multimeter I always have a small negative Voltage (about -30mV; thats probably why the Limiter LED is on and the Outputvoltage is Cut to 0V).
Do you have any Idea at which part of the circuit I should begin to look for that bug to get it fixed?
I've made a short video clip to visualize the problem: 


best Regards,
peter

 

[audioguru2]

The regulation of current works as well, but if I turn the current pot all the way left (minimal current) the current limiter LED turns on (although there is no load at all connected). It doesn't matter in what positions both Pots are, my selfmade Volt and Currentmeter measures a small current from less than 10mA. That current is mesured and calculated over the voltage over R5. If I measure the Voltage over R5 with my multimeter I always have a small negative Voltage (about -30mV; thats probably why the Limiter LED is on and the Outputvoltage is Cut to 0V).
Do you have any Idea at which part of the circuit I should begin to look for that bug to get it fixed?

I do not know which schematic you used. R5 in the original schematic and in my modified schematic has nothing to do with current regulation.

The opamp for the voltage reference and its zener diode have currents that go through the 0.47 ohm current-sensing resistor. The opamp for current regulation has an input offset voltage that is not cancelled so maybe the 33 ohm resistor value needs to be increased so that the small currents are not detected.

 

[pete1990]

hey,

thanks for your answer. I'm sorry, it's R7 I was talking about...my mistake. I will have a look at the 33 Ohm resistor and I'm using the original shematic (

).

peter

 

[audioguru2]

The original schematic and parts list have many errors. The result does not produce 30V at 3A and is not reliable.

 

[red_81]

Hi guys,

I almost started to do a schematic ver.0 (the one from kit) and than stumbled upon this thread. I read it from firs to last page. What to say, u saved my life. I did PSU on last version with MC34071 from ebay and used it in school where kids do a lot of short circuits during practice and this nice piece of design survived 2 years of daily torture. I got a bit lazy to bring it home->job->home... so i decided to make another one.

My problem is that there is no more ICs to find anywhere at reasonable price tag, neither  MC or TLE variant. They were like 1$/piece but now i cant to find them anywhere. I live in EU and shipping from USA is insane so im kind of stuck!
Any suggestions? Some replacements for IC s? im trying to find something on my own but no success.

tnx in advance

Ps: one more time, big tnx to audioguru, redwire, picmaster and all others for effort on this one

 

[redwire]

What about Farnell/element14/Newark?  very common part

 

[audioguru2]

ON Semi stopped making the MC34071 opamp in a through-holes case.  Digikey and/or Newark might still have some left. It is now only tiny and surface-mount that might get too hot in this project.

The TLE2141 is still made in a through holes case. Almost all parts distributors have some.

 

[nekhbet]

I found the project on google then I saw the forum and I'm a little bit confused .. can someone please tell which is the current version of the schematics?

Thank you!

Happy Holidays!

Sorin

 

[audioguru2]

Here are the latest schematic and parts list again:

View attachment 41986

View attachment 41987

 

[redwire]

I'm working on a smd version of this board with the TLE2141ID chip.  The only thru hole components are the BD139, bridge rectifier, and R7.  I plan to use a MJ11016,  a darlington power transistor with a minimum gain of 1,000 in lieu of the  2N3055.  Sure you may loose 0.7 volts on the output but with the 28V transformer there is enough headroom to still get 30V.  I don't think the BD139 will even need a  heat sink.  Waiting on a few parts to assemble.

 

[audioguru2]

Hi Redwire,
Will the tiny surface-mount TL2141 for location U2 survive the heat?