Newbe has stumbled in

Discussion in 'General Electronics Chat' started by dlt123me, Feb 17, 2014.

  1. dlt123me

    Thread Starter New Member

    Feb 16, 2014
    6
    0
    Hi all, as the title suggests, I am a newbe to electronics and am just starting to learn.

    I tried to search the forum for my question, but was unable to get a search result. Not sure if it was my user error or if the db has too many entries titled Power Supply... but whatever, I couldn't get a result.

    Since I am starting out in learning electronics, can anyone suggest a good, inexpensive bench power supply that will not cost an arm and a leg? A supply that can deliver ~20V with 3A abilities.

    I have searched Amazon and other places for a good PS, but most in the price range I am looking at, are trash from what I deduce from those who have bought them.

    Is there a good PS for the beginner that is safe, accurate and inexpensive? I am looking at spending $50 - $120.

    Also, suggesting I build one is out the question at this point in my electrical abilities.

    Any suggestions?

    Thanks,
    Dennis
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
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  3. crutschow

    Expert

    Mar 14, 2008
    13,001
    3,229
    This is a 5A, 30V supply that got fairly good reviews.
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,737
    4,789
    Why is that? The very first electronics course I took the first project was building an adjustable 3V to 15V, 3A supply. Basic power supplies are not too hard to understand or to build, plus you can do it pretty cheaply and you learn a lot along the way.

    You don't need to design one at this stage. There are plenty of schematics, complete with decent bills of material, out there for the taking.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    You will never go wrong with a good "laboratory" style power supply. My preference is for separate course and fine adjustments (so I can grab coarse and turn it off fast).

    My personal favorite is one with 3 outputs: 0-6V @ 3A, and 0-24V @ 1A, add adjustable, readable on internal meter, all floating. Just makes life easier.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,036
    An alternative to consider is to just use an old computer PSU. They are essentially free and you might even get paid to take away an old computer for recycling. A computer PSU can supply lots of amps at 5V and usually at least a couple amps at 12V. For low current, you can even use the -12V side against the +12V. There are lots of folks tweaking them to get more than +12V also.

    It's not as versatile as a real lab power supply, but free and easy. Just use a LM317 to get variable voltage and you can even build your own constant current supply if you like.
     
  7. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    I don't want to damage the experimenters power supply manufacturing industry, but how about that, kind of a kit:

    -Laptop adapter 20V
    -Buck converter PCB from eBay, replace 10 turns trimmer with a pot (there are also more expensive one's with current regulation)
    -Also boost converter if needed, the small one's are cheap
    -LED display modules for voltage

    Current regulation is not really much needed, what I suggest instead is more than one buck converter, so you can use multiple voltages.

    Mount all the stuff into an enclosure.

    costs you half the money and is much smaller.

    Normally these days I add a tiny buck converter PCB to the circuit, and just use any wall adapter, laptop adapter, or electronic transformer.

    I really generate voltages I need inside the circuit with LM2576, Mc34063 etc.

    Yet if you want to experiment with motors, coils, amplifiers, OpAmp you need +/- supply, and maybe also current regulation.

    So, maybe go for a small ready-made power supply, it is unusual to need more than 1A for small circuits.

    At least for microcontrollers or small LED circuits. These only need low voltages, and even if they need higher voltages, often only small currents.
     
  8. dlt123me

    Thread Starter New Member

    Feb 16, 2014
    6
    0
    Wow, there are some good ideas here. I like the idea of making my own, but I am just learning to understand Ohms Law, and do not want to make a mistake in building one at this time.

    I've learned, the hard way, that electricity should be respected and I just don't have the experience to know with certainty what to do and not do.

    Once I have more experience under my belt, I will think like most here, i.e... "Come on boy, this is an easy project", but I just want to be careful at the level I'm at now.

    I suspect that eventually I will build a power supply just as a "right of passage" project... but in the mean time, I need to buy a professionally made unit for peace of mind. Someday I will make my own V=IRsion. :D

    Thanks for the feedback and if anyone else has any suggestions please pipe in..
    Dennis
     
    Last edited: Feb 17, 2014
  9. dlt123me

    Thread Starter New Member

    Feb 16, 2014
    6
    0
    You're just taunting me right? :p I've seen some 3 output units that aren't too expensive. What unit do you use Ernie?
     
  10. dlt123me

    Thread Starter New Member

    Feb 16, 2014
    6
    0

    Thanks, this is a good direction to go. I've done some good rabbit trailing with these links.
     
  11. Veracohr

    Well-Known Member

    Jan 3, 2011
    550
    75
    My first project was the PSU I use. It's only +/-15V, 1A, has no number reading for the voltage (I have to use a multimeter to set it), and in the long run probably cost me more than the first one linked above. Not really worth building your own unless you're doing it for fun.
     
  12. #12

    Expert

    Nov 30, 2010
    16,277
    6,788
    My first project was assembling oscilloscopes for an engineer at General Motors, but that doesn't mean everybody can do that. Apparently this guy needs to experiment with the bits and bobs before he has some confidence. I can respect that.
     
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  13. dlt123me

    Thread Starter New Member

    Feb 16, 2014
    6
    0
    Hi all, I've been looking for a good bench power supply and I was made aware of this by a Youtube video. This unit looks really nice.

    I've been looking for a used version of Thurlby Thandar PL303 power supply, but haven't had much luck. I live in the US and need a 110V unit.

    Does anyone know where I can purchase a used or refurbished 110V version of this power supply?

    If anyone is interested, here is a link to the Youtube video about this PS.

    http://www.youtube.com/watch?v=XCT2OlpKb7s

    Any help is appreciated...

    Thanks,
    Dennis
     
  14. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    As long as were talking PS reviews.
    I rate this one at the top.
    Don't remember where I got it. Must be surplus as there are calibration stickers on it.

    http://www.ebay.com/itm/Topward-3603D-DC-POWER-SUPPLY-0-60V-3A-/370043054492

    I'm sure I didn't pay that!

    I think I chose it because of the 60V max out.

    I've shorted the output on this a hundred times. Crossed grounds blowing blowing the breaker feeding my bench a dozen times.

    There is no reason this PS should be alive today:eek:

    Use it every day.
    I believe someone mentioned earlier that current limiting wasn't that important.

    I totally disagree.
    From charging batteries to repairs like the strobe light I did today.

    Set the current limit and go nuts. You won't be frying components or have unexpected startups.
     
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  15. #12

    Expert

    Nov 30, 2010
    16,277
    6,788
    Reminds me, somebody said, "A power supply with out current limiting is a fuse".
    Absolutely! Get something with current limiting or a large box of fuses. :D
     
  16. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Should say, adjustable and metered current limit.

    That reminds me.
    My old one is stashed somewhere.
    Time for the flea market maybe.:)
     
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