First project idea?

Discussion in 'General Electronics Chat' started by KT6G, Dec 27, 2010.

  1. KT6G

    Thread Starter New Member

    Dec 20, 2010
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    0
    Hello All,

    I am venturing into electronic exploration for fun and to learn a few things along the way. I figure the that if I build as much of my own test equipment as feasible, this would be a huge step in the right direction.

    My interests are in RF/HF band (Yes, I am a HAM), Audio (Built my own SE tube amp), and general mayhem where applicable (as long as no one gets hurt)

    My thoughts of late are centered around BENCH POWER SUPPLIES and how to make a real darn good one. To ease my cranial traffic jam after looking high and low at many projects on the net, I wish to pursue a design that has a PCB already designed and proven.

    The project can be a bare bones PCB that one populates themselves or a kit that offers bells and whistles.

    With as many geeks as there are on this board (I have an inner Star Trek child wishing to get out) I was hoping for some real good recommendations for bench power supply PCB/kit suggestions?

    Another thought was flea-bay, in that buying an old HP bench supply for parts and recycling some of those parts into a newer design with IC's and LCD display? Really do not know if this is the right path to head down, but taking things apart is real fun, IMHO. :D

    Thanks for reading and when I get this project going I will give an update as needed for my benefit mostly and maybe help someone else possibly?
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    I just designed a very basic power supply circuit for a guy on another topic, it could of course be varied in so many ways it isn't funny:

    http://forum.allaboutcircuits.com/showthread.php?t=47534 Circuit is on the second page of posts.

    Values are just common sense from the data sheets and basic knowledge but if I need to I'll eventually write up a bill of materials on it. The final circuit is on the second page of all the posts but I haven't bothered to figure out a PC board on one yet since there's so many variations one might want to use. It could easily be made on simple perfboard for all that matters.

    You going to be working with any tubes? If so it's getting next to impossible to find an old tube TV set to scavenge the power transformer from. Filament transformers are still easy enough to find but to make any sort of high voltage I'd suggest hitting up some of the industrial electrical supply surplus stores and picking up a few control transformers. These were designed to convert 240, 277 or 480V down to 120V and go from a around 100W all the way into the KW range. If you hook one up in reverse 120 becomes a nice selection to rectify, add a variac if you want it to be variable or just build a regulator circuit for the secondary output(s).

    They're also nice to use in the opposite direction as well, 120 into the 480 input will give you 30V out at an extremely nice current level considering you can often pick up a 1 KW one for $10.
     
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,696
    904
    A lot of people seem to want to build a bench power supply as their first project. When you were learning how to drive, did you start by building the motor from scratch?

    I suggest getting a simple supply. I got a cheap wall wart with regulated, +5, +12, and -12V from Motorola. Unfortunately, it is no longer made, but similar ones are still available from surplus places. Then have fun building stuff.

    John
     
  4. #12

    Expert

    Nov 30, 2010
    16,304
    6,813
    Guys, there is a whole industry about antique valve amps. Speaking of antique...Antique Electronics Supply. I got every strange thing I needed to build a Champ/Supro stlye of amp there, including the grille cloth and the antique looking jewel light.
     
  5. Wendy

    Moderator

    Mar 24, 2008
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  6. KT6G

    Thread Starter New Member

    Dec 20, 2010
    2
    0
    Thanks everyone for the reply's.

    Mr. Marsden,

    I have read your primer on basic PS and was really wanting to go a step further with a PS that is truly a superb bench top PS. I do admire your work and I am grateful for your many, many contributions to this forum. I also must say, "Brother", that the Square and Compass immediately caught my all-seeing eye. Calaveras Lodge #78, CA, F. & A. M. Current Tiler for 2011.

    Mr. Marshall,

    You seem to be zeroing in on what I am desiring to achieve. No tubes in this supply thanks. I wish to incorporate many zings and zangs for a true work of art PS. I should list some desires as to what I wish to achieve.

    1. Dual output supply with V and I adjustable regulation from 0-30v and up to 4a.
    2. LCD Graph display with 5 digit resolution for each output node.
    3. Very, very low ripple on the DC.
    4. Tight tolerances on regulation, within +/- .1 % or better.
    5. Soft start circuit.
    6 Possible Frequency counter incorporation?

    And any other ideas that anyone else may have to make a really nice PS for the bench.

    Mr. Jpan,

    This would not be my very first time with working with electrons. I do know that electronics is theory and most old hands know that it is smoke that runs inside the wires. After all, short a circuit and electrons to not pour forth from the fault, but rather smoke rises into the air.

    Mr. #12,

    First, love the user-name, seems to fit well with the forum. I have quite a collection of vacuum tubes and collected them for awhile, but not anymore. I built a system based on 300b's SE output. Very nice indeed. My only interests in tubes these days are the RF amplifier types. As I progress in my study, I wish to pursue Software Defined Radio systems for HF bands. This seems to hold the most promise for the future for Amateur Radio,IMO.
     
  7. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
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    1. Dual output supply with V and I adjustable regulation from 0-30v and up to 4a.
    2. LCD Graph display with 5 digit resolution for each output node.
    3. Very, very low ripple on the DC.
    4. Tight tolerances on regulation, within +/- .1 % or better.
    5. Soft start circuit.
    6 Possible Frequency counter incorporation?


    That would take a decent amount of work, especially #4 and I'd leave the freq counter as a separate project.
    Certainly a doable project but I sure don't have the time to tackle making up a design for it.
    If your funds aren't really that limited you might try looking around http://www.techrecovery.com or even calling them as they don't advertise everything they have hiding around.
     
    Last edited: Dec 27, 2010
  8. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    One of my long term projects is to take a very inexpensive power supply sold by BG Micro and turn two of them into a dual variable power supply. I'm not talking about modifying the modules, but adding a variable regulator onto it.

    [​IMG]

    24VDC 6.5A $14.95

    http://www.bgmicro.com/PWR1278.aspx

    Always good to meet a fellow brother. We have several here, some are incognito.

    Just a suggestion, add your approximate location to your profile similar to mine. It will help when we refer you to parts sources.
     
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Biggest problem he's going to have to face is reality.

    Tight tolerances on regulation, within +/- .1 % or better.

    That would require some complicated temperature feedback as well as rather precision components all the way down to vernier pots of the highest quality which, last I looked, don't come cheap by any means. I guess if he can afford to build an amp out of 300B tubes then money isn't as bad as it is for most of us - especially people like me with multiple hobbies, expensive girlfriends and not being able to work on freelance stuff anywhere as much as I used to. At least I'm done building all the new computers I wanted to this year, got through all the Holidays and hopefully have finished all the expenses involved with the antique motorcycle I've been restoring.

    For experimentation I'm quite happy with all the test equipment I've collected over the years, none is "state of the art" but quite sufficient. I hope to have some projects on a limited open market early next year and that will provide a bit of extra income. At least I've got a fairly good paying regular job, so many have been without work it isn't funny and we were hit far less than most states were.
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I'd suggest a LC Meter Kit first, since you mention you are into RF.

    Then maybe an ESR meter test tool due to the number of bad caps around if you'll be getting stuff from eBay or repairing broken stuff.

    After that, Bill's blog link above has a ton of light projects to get started for next year's Christmas lighting. ;)
     
  11. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Nice design, but my $20 one from eBay is plenty accurate for what little I need to use it for. I may occasionally use scrounged, surprise box or parts I've had sitting around for years in occasional simple prototype situations but I always tend to check them out first, in most cases I just go ahead and order fresh components as they don't cost that much from the reputable suppliers.

    I wouldn't hesitate to get 5 digit LED/LCD Chinese panel meters from eBay but be aware that many require an isolated power supply.

    +/- 30V at 4A with resettable current limiting is going to take bypass transistors with additional circuitry and to get extremely low AC ripple is going to take a lot of filtering, perhaps even a twin T arrangement that includes inductors. The alternate of course is to go with something like Bill suggested above which will be a switching supply thus far easier to filter. I've just got a couple of old Lambdas from the surplus age, 10 turn pots, only conventional meters but quite sufficient for my needs because if something goes into the real world it'll never have anything better powering it.

    On an old workbench I used to have a couple of car batteries underneath, switched to where I could have +/- 12V or + 24V and charge them at will when I wasn't using them. To each their own though, try that link I supplied as they've got precision.
     
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