0-30V Stabilized Power Supply

[karthikeid]

hi effenberg

ill the post the complete components list and the schematic with the pcb i made on monday...

 

[audioguru2]

I also understand the original project was wrong and the version using OPA445, which Audioguru posted part lists at http://www.electronics-lab.com/forum/index.php?topic=19066.msg87812#msg87812 was also not correct.

No.
I simply fixed all the errors in the original project so the modified circuit worked perfectly and reliably. But the OPA445 opamps were expensive and frequently not available.

The latest version uses common inexpensive opamps from either of two manufacturers.

Audioguru posted the latest schematics ans parts list for the correct version at http://www.electronics-lab.com/forum/index.php?topic=19047.msg87749#msg87749 at Aug 19, 2009. Schematics show the new opamps, so I believe those are really the latest files. However, Redwire posted a parts list at http://www.electronics-lab.com/forum/index.php?topic=19066.msg88462#msg88462 at Oct 11, 2009 that has some differences to Audioguru's.

It is the same circuit but maybe the calibration trimpots are in different locations. I did not compare the parts lists. It will be simple for you to post the differences.

I must make sure the project I select works to its specifications before I submit it as my project for the entire year.

It works perfectly when built by an experienced electronics person. most Noobies had problems with it.

- Are the parts lists posted by Redwire targeted at a 5A PS?

Redwire made a 5A power supply. Everybody else made the latest 3A power supply.
The differences are very small.

- Are these really the latest schematics and parts lists or I am missing another version at another thread?

My schematic and parts list are the latest.

- Audioguru mentions at http://www.electronics-lab.com/forum/index.php?topic=19066.msg87814#msg87814 the schematics is missing a 10V Zenner diode. Is it?

Yes it is missing a 10V/1W zener diode that is shown on the schematic.

- If built according to the correct schematics and parts list, which you're hopefully pointing me to, will this project supply 0-30V at 3A with low ripple, no overheating and, of course, safety for use in students workbench?

Yes if you use large enough heatsinks that are mounted correctly.

- We were supposed to deliver PCB design along with schematics. I see at http://www.electronics-lab.com/forum/index.php?topic=19066.msg88538#msg88538 that Hero999 mentions the PCB was lost. Redwire posted a PCB file at http://www.electronics-lab.com/forum/index.php?topic=19066.msg89170#msg89170. Is it the right one?

Make Redwire's pcb if you want. Then use his schematic and parts list.

 

[redwire]

Hi effenberg0x0.              There are insignificant differences between audioguru's part list and mine.  Mine reflect preferences rather than errors.  I wanted to have a little more range so I used a 0.27ohm power resister instead of the 0.49 ohm in the original.  Some of the calibration pots may have different values to fully utilize the increased amperage range but both work.      After adding the 10V Zener, I reduced the value of R22 because it no longer see the output of the transformer.  R2 got pretty hot so I increased the resistance a bit.  The sketch attached to my post is Audioguru's so there should be no difference in the pcb.

 

[corsa]

Hi redwire, good afternoon, i will make your pcb and i have some questions about down traces, on left side of pcb. The trace descontinued should be continuos? And they be intesect D1 of bridge, right?
And R7 are conected to C1 ground, right?
I make this changes, please, can you tell me if i right?

Regards

PS-6_Changed.rar

 

[effenberg0x0]

Thank you Audioguru and Redwire. This is the info I needed.
Karthikeid: I'd appreciate that. Thanks!

Hopefully I'll be able to contribute to this forum in the near future.

Regards,
Effenberg

 

[redwire]

corsa     The area contained  in the blue shape on the left hand side of the pcb should all be a solid blue ground plane.    I used an earlier version of EAGLE  to create the pcb and I had to down load the latest version to open your copy.   You need to take the original version I posted,  and hit the Ratsnest button and it will fill.   The copy you posted looks like you altered something because it does not fill properly.      

 

[corsa]

Thanks redwire, i'm learning to work with eagle, sorry my mistakes  ???
I used the Ratsnest button like you said, and created this solid ground and i think its more logical!

PS-6_Original1.pdf

 

[redwire]

corsa,  That looks correct.    If you notice a few extra holes or pins it's because I added a few to connect the LCD display and one led connection for your front ase.  It will work with or without the pins installed.

 

[effenberg0x0]

Hi guys,  

In order to understand the differences between the original project and the two versions (updated 3A and 5A) I have built a table comparing parts, according to Redwire's and Audioguru's parts lists. I thought of posting it here, so that maybe it might help other newbies. There are in fact many differences (about 60% for 5A project and 40% for fixed 3A). I'd appreciate if you could have a look at it. I am gonna go for the 5A project.  

The ZIP file holds the original XLS file that generated the PNG, in case anyone wants to make changes.

Regards,
Effenberg

EDIT: Attached file was updated at December 11th, 2009. Reason: Correct transformer specs for Redwire's parts list.

View attachment 40744

 

[audioguru2]

Hi Effenburg,
thanks for the comparison that shows both almost the same.

 

[karthikeid]

here is the circuit, the parts list are the same as such in the above post.....
no change...
u can start doing the circuit...

View attachment 40736

 

[effenberg0x0]

Hi Effenburg,
thanks for the comparison that shows both almost the same.

And yet very different from original design. Before I landed here at this board, I saw many blogs and websites in Portuguese, Spanish, Italian, other languages, in which people were building the original version and complaining about the results or building mixed versions, unaware of the correct parts list. Power supplies are obviously very popular with newbies like me - a first real project, primary need in the workbench.

Let me ask you guys a couple more questions:

- How does this PS compares to professional ones? They're very expensive! What do they have that this one doesn't?

- From a more experienced point of view, what do you see as the weaknesses of this projects?

- The original project mentioned adding voltmeter + current meter with LCDs through this project: http://www.electronics-lab.com/projects/test/022/index.html . Did you guys ever built this add-on? It seems doable, but soldering SMD components neatly is still hard for me. Shaky hands.

Kind regards,
Effenberg

 

[effenberg0x0]

here is the circuit, the parts list are the same as such in the above post.....
no change...
u can start doing the circuit...

Thanks karthikeid! Actually after submitting this project as my goal at the course, next 2 months will be 6 hours/day and 6 days/week of Malvino's book now... It's all theory, some use of eagle, for a while until they let us start building it. We must be able to describe each components behavior, analyze the circuit basically, predict output, etc before giving it a go...

Thanks for the schematics!

Regards,
Effenberg

 

[audioguru2]

The original project is a kit. The kit maker must get a lot of complaints of it not working properly, many parts getting too hot and poor reliability.

 

[effenberg0x0]

OIC...
Audioguru, do you believe it would be possible to build this project on a plastic case? Or is it too risky?
When you people mention the heat generated, I am not sure how many degrees you are talking about.

Thanks

 

[audioguru2]

When the current is 3A then R7 dissipates 3A squared x 0.47ohms= 4.23W.
Q2 dissipates as much as 2.3W when the output is 3A and is shorted.
The output transistors dissipate a total of 117W when the output is 3A and is shorted.
That is a lot of heat.

 

[effenberg0x0]

OK, Thanks. I'm gonna try an aluminium case with a large heatsink and possibly a cooler/fan.
Can I use thermal paste like Artic Silver? I come from IT, we use that on CPUs.

 

[redwire]

effenberg wrote:

The original project mentioned adding voltmeter + current meter with LCDs through this project: http://www.electronics-lab.com/projects/test/022/index.html . Did you guys ever built this add-on? It seems doable, but soldering SMD components neatly is still hard for me. Shaky hands.

Why don't you build the non SMD version that is linked to the above site. Original design page located here: http://elfly.pl/multimetr/multimetr_en.htm

Yes,  several have built is successfully.  I have a non smd LCD version working on mine.    I'll post some pictures later.

 

[effenberg0x0]

Redwire: Please post the pics, it helps a lot!

Guys, I am having trouble finding C1 (12,000 UF / 63V electrolytic). I know I can use 3 caps, as you mentioned, but I haven't found 4,000 uf / 63V.

I know Cx=Cn+Cn'+...+Cn'', in theory, but the units I have are 3,300uf/ 63V and 4,700uf / 63V.
So using (2 x 4,700) + 3,300 I'll get 12,700... Is it ok?

Thanks.

 

[audioguru2]

A 12,000uf/63V capacitor is available in North America at Digikey or Newark.
You can add smaller capacitors in parallel if you want but then their total cost is more.
The capacitance can be higher then the project will work better.