0-30V Stabilized Power Supply

[lighty]

Ok, the POTs are working fine, just that when the current is turned down to 0, the limiting LED turns on, could this be because C7 is an electrolytic type?

[audioguru]

Ok, the POTs are working fine, just that when the current is turned down to 0, the limiting LED turns on, could this be because C7 is an electrolytic type?

With the current-setting pot at minimum, a load of 12mA or more will cause current regulation.
Maybe C7 leaks as much as 12mA or more because it is connected backwards or because it is defective?

Opamp U3 is a TLE2141 with a max input offset voltage that is much too low to cause your problem. Maybe U3 is a counterfeit one or is defective?

[lighty]

With the current-setting pot at minimum, a load of 12mA or more will cause current regulation.
Maybe C7 leaks as much as 12mA or more because it is connected backwards or because it is defective?

Opamp U3 is a TLE2141 with a max input offset voltage that is much too low to cause your problem. Maybe U3 is a counterfeit one or is defective?

Cool, I'll try replacing it. I did notice when I was fiddling with the setting that the output dropped to about -0.3 V.

I think I will try replace C7 1st then test it again, perhaps the offset is way off?

[PicMaster]

This is the connections drawing for my version of the power supply and updated schematic, To me it looks quite simple
This is the actual size of the PCB and what the layout looks like.
The next thing is to update the component values on the schematic and create BOM
Hopefully over the weekend I shall get PCB made and assembled

POWER_SUPPLY_V2.pdf

power_supply.pdf

[PicMaster]

I've got it 3/4 built, I missed some parts off and by the time I thought about it Maplins was closed.

will try and get them tomorrow (Monday) then I will be ready for testing and if all goes well I will upload  the pcb

picmaster

[Scooter_3D]

Hi all, here is a rendering of the board im going to be making.
It is a similar in design to the original....

[PicMaster]

Here is the working version on my PSU, There is just just a couple of minor things I have got to look into and clarify. Yes the connecting wires may look a little on the light side but this is for testing only Has I only took to 3amps and calibrated max current for a few seconds to try.

These are the minor things that I have got to look into.
1. Because I'm using a 30V transformer the voltage is slightly to high feeding the op-amps has the TLE2141 is only rated at 44V I got 48V.
2. With the current pot set to Min the limit LED comes and and this restricts the voltage I have to turn it up slightly(not sure what the voltage is at the center of the pot has it is getting late.)

Aslo I'm not sure if this is normal if the limit LED should light up with the pot to min, I did disconnect C10 has if I remember lighty  had the same trouble but it is still the same

I get full control over the current range min current is about 40ma, I did see that is should only be 12ma, I will have to make sure that I've got all the correct components in place first and I will read through the older posts.

[audioguru]

These are the minor things that I have got to look into.
1. Because I'm using a 30V transformer the voltage is slightly to high feeding the op-amps has the TLE2141 is only rated at 44V I got 48V.

A half-decent 30V/127VA transformer is 31V with no load which produces a positive unregulated supply of 42.6V. Since your unregulated supply is very high at 48V then either your transformer is poor or your mains voltage is too high.

[ultima2009]

Picmaster, can you upload the pcb and BoM?

[PicMaster]

Here is my vesrion of the power supply comlete.
PDF file is a new BOM(for this project only),PCB copper side, PCB overlay, assembly drawings

Please let me know if you find any errors or suggestions

Picmaster

[PicMaster]

I forgot to add the latest schematic to the PDF file

Picmaster

Schematic_Prints.pdf

[Skleb]

PDF file is a new BOM(for this project only),PCB copper side, PCB overlay, assembly drawings

I don't see any of these.
Please, can you upload PCB copper side?
Thanks

[mauriciovargas]

Hello guys. Firstly I have to say how you've helped me with this project. I've built the original project and it was such a fail...

So, I have a doubt: If I use a  24VAC/435 mA transformer on the audioguru's project (3A), it will work? It's all I have here :(

Brazil regards!

[audioguru]

For 30V output, the transformer must be at least 28V.
For 3A output, the transformer must be 4.2A.
The power from the transformer is 28V x 4.2A= 188W.

The power from your tiny little transformer is 24V x 0.435A= only 10.4W which is 14 times too small.
Your transformer will power a project that goes to 25VDC at 300mA. If you do not change the value of R7 to prevent it from trying to go to 3A then either the transformer will get extremely hot then burn out or it might catch on fire.

[mauriciovargas]

Thanks audioguru.

So, I can use any transformer on the project, but it will work at a limited power? All I need to do is change R7 and everything is gonna be OK? What more do I need to change?

[audioguru]

So, I can use any transformer on the project, but it will work at a limited power? All I need to do is change R7 and everything is gonna be OK? What more do I need to change?

I don't know if you are making the original faulty circuit or which improved circuit.
Since your transformer is so small then you can make a simpler low power circuit.

[mauriciovargas]

Audiogurus, I'm doing the improved one. I did the original and now I have all the components waiting for something. This is why I want to do the good one. Actually my idea is use a transformer with 2A or around it. So, will it work?

Another question: Can I use a smaller capacitor than that ones with 6.800 uF? They're very expensive and if I use a smaller transformer I think they'll be unnecessary.

Thanks again.

[Guest Enforcer83]

Mauriciovargas,

You can use a smaller capacitor,  but you will induce a greater ripple voltage into the system.  There is an equation that you can use to determine the ideal value for a capacitor given the desired ripple voltage and system current.  However, this equation eludes me at the moment.  Try doing a search for voltage ripple in google.

I will update when I find the equation.

[audioguru]

A 2A transformer is also too small. Then the max current from the project will be only 1.4A DC.

I have a graph that shows the amount of p-p ripple in a full-wave rectifier with a 60Hz mains and with various sizes of filter capacitors:

[mauriciovargas]

Thanks audiogoru and Enforcer83.

I already know the ripple problem with a smaller capacitor and a big current. But,what I meant to say, is that I don't need more than 1 A. So, can I use this project (audiogoru's 3A version) with my little transformer (24VAC / 435 mA) and a smaller capacitor, like 3300 uF? What more I need to change in the project?

[audioguru]

With a max output of only 300mA and a max voltage of only 25VDC then the two 2N3055 transistors can be a single TIP31 transistor on a heatsink that is not very big.

[mauriciovargas]

OK. I already have the 2N3055 so I'll use them. My idea is use the little transformer just for a while. When I can afford, I'll buy a good transformer and the 12.000 uF capacitor.

Thanks for everything.

[Guest Enforcer83]

Ha,

Audioguru's pic has the formula I was looking for. :)

[mauriciovargas]

Hi guys...

I was thinking better, so I won't do this project right now. Do you know a good project for a small power supply? Like 0~24v 1A with current protection or something like that?

Thank you

[audioguru]

There are many cheap weak little power supply projects on the internet. Some work but many don't.