effenberg0x0

Agreed. Had to opportunity to see the defacement part of it.

Some posts in some threads are missing, including this one. I believe two/three pages of posts here. Mixos said it was a hack attempt. At least we didn't lose everything this time.

LOL, I am, I am. Just having a bad week. Xmas is not a happy holiday for me at all. Here we go: YEY!!!!!!!!!!!!!! A new PSU!!!!!!!!!!!!!! Thanks Santa!!!!!!!!!!!!! :D :D

The link for the project discussion, in the original project page, was updated to point here. This thread content beats up any FAQ IMHO. There's a recent post in this thread in which someone posted a block diagram of this PSU. It might help newbies. Hero et al are discussing a new 0-30V PSU in a new thread. I'm sure something interesting will come out.

Audioguru, You obviously have a very detailed understanding of the circuit and expected behaviors. Do you use Spice or other software for these analysis?

The original is 0R47 5W. Your's (fixed 3A version) is also 0R47, but 10W. Do you think two 0R27 10W in series is still too little and risky? Thanks, Effenberg

For the 3A version, R7 is 0R47 10W. I got 0R27 10W units. If i put two of them in series I get 0R54 and better heat dissipation (two components instead of one). But what would be the downsides?

As the voltage oscillates in the outlet, I can also see voltage changes in the Power Supply Output. Voltage in the outlet oscillates a lot more than I thought, about twice every minute +1 to +4V. Can't still calculate how much oscillation this creates in the PS output (single channel multimeter). A first idea to fix this was to use a Voltage Regulator such as this: http://www.apc.com/products/category.cfm?id=12&subid=57 Or maybe you have any tip to make the PS output stable despite AC voltage changes in the outlet? Thanks, Effenberg

Has any of you ever used these "PC OScilloscopes" that use the PC USB port? What about even cheaper units, that use the PC Mic In port? I'd like to hear some opinions on the quality of these things but can't find a user.

Pi (π) ? :)

I think any decent Power Supply project built correctly will be better than commercial units. I'd say more than 90% of the commercial units I see in the market are cheap things that don't look like they will last 6 months. And, of course, it's always more entertaining to build it, no matter the price and time spent. That's why we're all here for anyway. For example, one of the features I'd like to add to this project are digital controls instead of potentiometers ("+" and "-" push buttons). Don't know how yet. It's absolutely unnecessary, but it's cool.

A good idea. My current heatsinks are so inadequate I'm considering leaving fans on non stop. Other options are Peltier modules, CPU coolers, etc...

Yes, definitely. I want my PS to have two outputs. and I got two LCDs here for the meters.

It will take a while for me besamartis. I have one month to write an essay describing the operation and importance of each component in this circuit, the main individual circuits, possible changes/updates, etc. A lot of it is still not clear to me and I have to study more to get it done. I have it assembled on breadboard and am using multimeter/oscilloscope to analise it. I'll go for the PCB and assembly only by the end of January... By then, I'll be happy to post all my material here for whoever may benefit from it.

Earlier today I had requested the admin of the website to update the wrong link at the original project page (it was ponting to a thread that was lost and not to here). It is done now. Maybe other users will read this thread before building the wrong project. Regards, Effenberg

Redwire said in a previous post that me made his unit using a microwave oven transformer. The unit was 7A or more I think. Actually I almost cried when I read this: If I had searched at repair shops, electronics dump places or even sites like eBay, I would be able to buy a broken microwave oven almost for free. Consider this option. Also think of other appliances that may have a suitable transformer. Another option would be to buy 2A transformers, if they're cheaper, and put them in parallel.

Any transformer up to 2A is common here and costs an average of US$8. 3A transformers are a little harder to find and were priced at an average of US$15. 4A are WAY hard to find. They were priced at US$30. 5A units were simply nowhere to be found. After searching for an entire week I found only four stores that had them, but prices were beginning at US$100. I had my 30V/5A units made for US$21 each. In the latest parts list, a 28V 4.3A, 118VA transformer is mentioned. So if you go for 30V 4.5 or 5A it will be enough.

Besarmatis, I couldn't find transformers at reasonable prices in the market here too. My solution was to have them built in a small shop that does it on demand. I managed to get two units for half the average price of a single unit in the market. They were built exactly to my specs (core, wire, windings, etc). Mine are 115V/230V - 30V 5A. Maybe you can find a shop like this there? Also, if you're putting them in parallel, its important that they don't differ much. I have posted some links that explain why. I would go for two separate transformers, simply because I may want to reuse one of them in a new project in the future (considering trafos are expensive).

Is it possible to modify the link in the original project that points to the lost thread so that it points to this thread? Besarmatis: I have posted a table comparing parts lists for the original, fixed and 5A versions some days ago in this thread.

Sorry, I'm new to Eagle. It was setup like this and I didn't know I could put a white background. Now I know, thanks. I have attached the new image. Thank God you saw it. I couldn't find TLE2141 or MC34071 in Eagle libs, so I used another opamp that has the pins inverted. Its fixed now. Yes, I was wrong to use pin1, but schematics I found in the thread show it at pin3. Is it 3 or 2? Fixed :) Lame mistake... Questions: 1)I have attached the list of Potentiometers and Trimmers in the parts lists of the three versions (Original, 5A, 3A). I'm confused to be honest. I'm building my version with two 30V/5A transformers in parallel and MC34071 opamps. In this case, I guess I should use 10K for RV1, 50K for RV2, 200K for RV3? 2)About the third Potentiometer (1K), I placed it in series with P1. Can you tell me if it is correct? 3)A serious problem: All schematics show an unnamed capacitor (0.1uf) between R19 and U3. I named it CX. I cannot understand why it would be there. Can you give me a hint? I have highlighted it in the attached schematics. Thanks

OK, I'm going for 5A version with transformers in parallel. This is my first Eagle attempt. I'd like to hear some opinions. I'm specially interested if you agree to RV1, RV2, RV3, P1, P2 values (I'm using MC34071). And if you see any mistake. Thanks, Effenberg Edit: Could not find P3, mentioned in Redwire's project in any schematics. Can anyone point me to it? Is it in series with P2?

>>Ebay has some very cheap bench PSUs by the way. Come on, don't take the fun out of spending 10 times more on components and building something that will obviously not work as expected at first time :)

Hi Alex, that is exactly the idea. The calculation is at http://www.electronics-lab.com/forum/index.php?topic=19066.msg89507#msg89507 and the idea of rectifying the output is a couple posts later at http://www.electronics-lab.com/forum/index.php?topic=19066.msg89517#msg89517. I was just worried about doing it because many technical docs mention the problem regarding small differences between transformers. But You and PicMaster convinced me. Regards, Effenberg

I have checked my transformers more carefully today. They are exactly the same in terms of materials and construction. However, one is giving me 31.7V and the other is giving me 31.8, same digital multimeter... Putting them in parallel will demand a rectifier circuit for each, with different resistors, to equalize outputs. Back to Eagle.

I've read this: http://www.eng-tips.com/viewthread.cfm?qid=14767 http://electrical-riddles.com/topic.php?lang=en&cat=4&topic=282 http://ecatalog.squared.com/techlib/displaydocument.cfm?id=7400DB0701&action=view http://www.ee.lamar.edu/gleb/power/Labs/Lab%2006%20-%20Transformers%20in%20parallel%20and%203-phase%20transformers.pdf Considering my two transfomers were made by the same shop, same machine, same materials, in the same hour, I am gonna bet their % difference is lower than 1%. An idea that caught my attention was: BTW: The LCD looks nice dude