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  1. effenberg0x0

    0-30V Stabilized Power Supply

    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...
  2. effenberg0x0

    0-30V Stabilized Power Supply

    >>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 :)
  3. effenberg0x0

    0-30V Stabilized Power Supply

    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...
  4. effenberg0x0

    0-30V Stabilized Power Supply

    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...
  5. effenberg0x0

    0-30V Stabilized Power Supply

    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...
  6. effenberg0x0

    0-30V Stabilized Power Supply

    Yes, exactly. I am curious about Redwire's transformer. I thought he had a 30V/5A. Anyway, I am considering no other way out now: I gotta use my two transformers and make it dual output somehow. I gotta study. Right now I am still thinking about the basics: 1) Primaries in parallel or in...
  7. effenberg0x0

    0-30V Stabilized Power Supply

    Ah wait a second... I bought two transformers 30V/5A. I was hoping to make two completely independent Power Supplies. Maybe I can use them both and still have 2 channels. I'll desperately need your inputs on that thou.
  8. effenberg0x0

    0-30V Stabilized Power Supply

    Oh Sh** ... Didn't thought of that. Wait, I thought Redwire used 30VAC x 5A? What's your trafo Redwire? PS: Checking the thread historic again: Original project trafo was 24VAC/3A, updated version was 28VAC/3A, Redwire's was 30VAC/5A. So 150VA / 42.4V = 3,5A (thats as far I I'll go, almost...
  9. effenberg0x0

    0-30V Stabilized Power Supply

    I think I'll have no option but to solder it very raised and hope for the best. I am giving up on these aluminium cased units... they are just a myth lol, no one has them at reasonable prices. Just so you have an idea, a standard resistor costs about USD 0.17 here (one unit). If I buy 10, 100...
  10. effenberg0x0

    0-30V Stabilized Power Supply

    Yeah, I'm kindda worried about the transformer in particular.. I couldn't find a 30V 5A unit readily available at a decent price, so I ordered a unit from a very small shop that manufactures them... It took them only 5 hours to make me one... God only knows the quality of this thing...
  11. effenberg0x0

    0-30V Stabilized Power Supply

    3A it will be then. Gotta make some changes, including this one, to the PCB. Eagle is kicking my ass right now. A new problem: I'm going for the 5A project and accepting Redwire's suggestion of three 2N3055, each with a 0R27 5W. The problem is that no shop here has these resistors with that...
  12. effenberg0x0

    0-30V Stabilized Power Supply

    The input voltage here is 120V. My trafo is 30V, 5A. 150VA / 120V = 1,25A Fuse. Is this the correct thinking? Another thing: I've noticed some of the few pics of the assembled boards in this thread show the ceramic resistor (10W) soldered like other components, I mean they're touching the...
  13. effenberg0x0

    0-30V Stabilized Power Supply

    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...
  14. effenberg0x0

    0-30V Stabilized Power Supply

    Audioguru, I am a little confused. I was thinking about Ohms law. If I = V / R and then V = I * R, decreasing the value of R would decrease the value of V, assuming constant I. Then why would the transformer voltage be higher without a load? Thanks, Effenberg
  15. effenberg0x0

    0-30V Stabilized Power Supply

    >>A 28VAC transformer might be 30VAC without a load. Noob question: Why? Are you considering the AC power oscillation in the primary? Thanks, Effenberg
  16. effenberg0x0

    0-30V Stabilized Power Supply

  17. effenberg0x0

    0-30V Stabilized Power Supply

    Thanks Audioguru. The problem is I have to use the pieces available at the course inventory. Redwire's 5A project suggests RS1506 (15A 600V) or GBJ2506 (25A 600V). They're also not available to me, so I am going for KBPC-3510 35A/1000V.
  18. effenberg0x0

    0-30V Stabilized Power Supply

    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...
  19. effenberg0x0

    0-30V Stabilized Power Supply

    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.
  20. effenberg0x0

    0-30V Stabilized Power Supply

    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
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