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0-30V Stabilized Power Supply


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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
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hi any updates to this project

Why do you show an LT1038? it is obsolete and is not made anymore. It is impossible for it to dissipate 32V x 10A= 320W. Its datasheet shows that with a huge heatsink with fan or with liquid nitr

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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



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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.

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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.

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In the Schematic posted by audioguru at the beginning of this topic, there is a 10V 10W Zener diode between the output of the Bridge Rectifier and the emitter of the PNP transistor.  I am confused with its purpose.  I have tried to analyze it using my circuit theory but have failed miserably, partially because I have always used regulators instead of diodes for voltage regulation.  So, what is its purpose?  A PSpice waveform would be very useful to help me visualize what is going on, if at all possible.

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In the Schematic posted by audioguru at the beginning of this topic, there is a 10V 10W Zener diode between the output of the Bridge Rectifier and the emitter of the PNP transistor.  I am confused with its purpose.  I have tried to analyze it using my circuit theory but have failed miserably, partially because I have always used regulators instead of diodes for voltage regulation.  So, what is its purpose?  A PSpice waveform would be very useful to help me visualize what is going on, if at all possible.

The 28V transformer might be 30V without a load on the project. Then it makes an unregulated positive voltage of 41V plus a negative -1.3V supply for U1. The total of 42.3V is very close to the max total allowed voltage of 44V and heats the IC. So the 10V zener diode reduces the max voltage and shares in the heating.
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It really isn't. I could order from Farnell but it would more expensive than all the other components (about 120USD!!). As I have to use the components they have at the course anyway, I selected 4,700uf+4,700uf+3,300uf = 12,700uf / 63V.

Electrolytic capacitors are normally only made in E6 values, i.e. 10, 15, 22, 33 and 68 but some manufacturers only make E3 values i.e. 10, 22 and 47 which is why you're having problems finding 12,000
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The 28V transformer might be 30V without a load on the project. Then it makes an unregulated positive voltage of 41V plus a negative -1.3V supply for U1. The total of 42.3V is very close to the max total allowed voltage of 44V and heats the IC. So the 10V zener diode reduces the max voltage and shares in the heating.


Be patient with me on this.  Power and power electronics are not my strong suit.  Low voltage battery systems are.

So you mean to tell me the Zener is adding 11V to the system.  That does not make sense.  Wouldn't the better option be to place say a 36V Xfmr with a no load rating of  38.52V in the system and connect the transistor, the resistor R19 and the V+ of the opamps to this rail instead?  Even figuring a Voltage drop of 1.05V at 5A through a bridge Rectifier (GBJ10005 is my planned rectifier) you are still dealing with 37.47V.  Yes it may be more expensive but at least the math seems logical.

I think I need a tutor to help me relearn this area of Electrical Engineering.  Doesn't help my circuit Prof. couldn't teach.
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So you mean to tell me the Zener is adding 11V to the system.

No.
A 28VAC transformer might be 30VAC without a load. Then its peak voltage is the root of two times 30V= 42.4V and the full-wave rectifier charges the main filter capacitor to +41VDC. IC U3 also has a negative -1.3V supply so its total would be 42.4V which is very close to its max allowed total voltage of 44v and it has a lot of heat.

The 10V zener diode reduces its positive supply to +31V and reduces its heat.


Wouldn't the better option be to place say a 36V Xfmr with a no load rating of  38.52V in the system ....

Then the positive unregulated supply would be +53VDC and everything will blow up.

Even figuring a Voltage drop of 1.05V at 5A through a bridge Rectifier ....

When the project has a 5A load then the average current in the bridge rectifier is also 5A.
But it conducts only on the peaks of the transformer's sine-wave for only maybe 10% of the time, so its peak current is 50A.
It has two diodes conducting in series so its voltage drop is about 2V.
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>>A 28VAC transformer might be 30VAC without a load.

Noob question: Why?

Because the windings have resistance. The output voltage drops down to the transformer's rating only when it has its rated load.

Test the output voltage of a 9V/200mA wall-wart. It is 9V only when it has a 200mA load but is 15V or more without a load due to the resistance of its windings.
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I did the tests (wall-wart). You are right.

Another stupid one: I've been checking projects of other students. Some of them have a fuse. On the other hand, I could not find a single power supply project on the net that has a fuse. Where do you stand? Should there be a fuse?

Also: It doesn't seem like eagle (last version) auto-track feature takes under consideration a decent space between tracks (potential capacitance?). Or does it?

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