Cheapest wall outlet to 12Volt 1Amp,.. need help

Discussion in 'General Electronics Chat' started by Kev5n24, Aug 3, 2009.

  1. Kev5n24

    Thread Starter New Member

    Aug 3, 2009
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    I need to power four regular 80MM PC case fans like this off a regular US wall outlet. Now to do this i have been buying 12Volt 1Amp power supplies like this, cutting the ends off, and wiring the four fans to the plug. This costs me about $4 a pop though and id like to find a cheaper way to accomplish this all. While searching for cheaper plugs i happened upon this 12V 1A voltage regulator and thought boy wouldn't it be nice if i knew what all to get and how to wire it so i could do this for a few cents rather then a few bucks since i already get 6ft lamp cords for .25 cents a pop. I'm pretty good with stuff like this, i mean i figured out the 12V 1A power supply thing by myself, and i know how to solder, but ive never worked with stuff like a voltage regulator so could someone please help me out with some links to all ill need to buy and wiring diagrams pictures?

    thanks
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    The transformer alone will be more than what you are paying for wall transformers. Plus everything needs to be placed in a case for safety. The wall warts are the least expensive way out.
     
  3. Kev5n24

    Thread Starter New Member

    Aug 3, 2009
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    I don't know what more then the 12V 1A voltage regulator ill need beenthere, but if you click that link i supplied you'll see there only .50 cent, and only .17 cents here for a 12V 1.5A voltage regulator which would probably really make my four fans spin nice and fast. Having the components contained wont be a problem either. Can someone hook me up with the how to though?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    OK.

    For starters, you'll need a power transformer that has a secondary of around 12VAC to 15VAC. These cost about $9 to $15 each at Digikey. Oops, you're already over budget.

    Then you'll need a pair of 1A rectifier diodes. Those are a few cents each.
    Then you'll need a large electrolytic capacitor, around 1,000uF. That'll cost you anywhere from $0.50 to $3.00. You will also need a capacitor from 0.1uF to 10uF on the output of the regulator.

    You'll also need a custom circuit board to mount all of this stuff on, that you'll have to design and order. Maybe if you get the quantity high enough, you can get them for under $2 each.

    You will also need a heat sink for the 7812 regulator. Another $0.50 to $1.50.

    You'll also need to have a UL approved enclosure for this line-powered accessory. You might find something for under $3 if you search long enough.

    But, MPJA (Marlin P. Jones & Associates) sells 12v 1A wall warts for under $3/ea if you buy them in quantity:
    http://www.mpja.com/prodinfo.asp?number=16419+PD
    About the same as just an empty enclosure would cost you.
     
  5. Kev5n24

    Thread Starter New Member

    Aug 3, 2009
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    You didn't even mention the .17 cent 12V 1A voltage regulator,.. so are you sure your way is the ONLY way to do this? If ALL those BIG parts are needed and they cost ALL that money then mind telling me how "MPJA sells 12v 1A wall warts for under $3/ea"? Someone once told me it was possible to do it cheaper and it makes sense that there is would be a way.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    You might find a cheaper source of wall warts in quantity, but I've found you get what you pay for.
     
  7. Kev5n24

    Thread Starter New Member

    Aug 3, 2009
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    ya i do buy in quanity, usually 25-50,.. but still don't see why i cant buy the litle parts inside one of them and do it myself. I mean these: 12Volt 1Amp power supplies like this are some pretty simplistic little things. So can someone hook me up with the how to or what?
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    Gee, consider that some of us put stuff together too, and are sensitive to costs. The economy of scale that lets a wall wart cost $3.00 occurs when the quantity purchased of each part is in the tens of thousands.

    Order a couple of shipping containers full of any part, and you statement -
    - becomes true.
     
  9. Kev5n24

    Thread Starter New Member

    Aug 3, 2009
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    i know you're a super mod and all,.. but your sarcasm still isn't warranted, nor is it helpful, or productive
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    That wasn't meant sarcastically, but to let you know that we might know a thing or two about prices. You did not credit us with being aware of how to hold down costs - or being aware of the wall transformer as being the least expensive device.

    You simply can't order in industrial quantity for the really big price breaks.
     
  11. Kev5n24

    Thread Starter New Member

    Aug 3, 2009
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    no offense but why should i 'credit u with being aware of how to hold down costs - or being aware of the wall transformer as being the least expensive device'.. i don't know if you're any good at those things. i asked how to do it and no one will tell me, just that its not worth the cost. maybe i can can keep cost down better then even you. not trying to be a dick im just saying let me find that out after you tell me how to build my own. i cant imagine it wouldn't have been quicker at this point to just tell me but what do i know about saving time or cutting costs ;-)
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    Wasn't the wall-wart made in China?
    The parts were very cheap and the girl who made it was paid a bowl of rice?
     
  13. someonesdad

    Senior Member

    Jul 7, 2009
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    Post deleted by poster.
     
    Last edited: Aug 3, 2009
  14. SgtWookie

    Expert

    Jul 17, 2007
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    Beenthere's been at this since I was a young kid. I'm probably older than your parents. I'm not saying that Beenthere's old - I'm saying that he knows what he's talking about via lots of training and practical experience.
    There have been somewhere between five and seven "wall-wart" power supplies made for every person on this planet. The number of these things that have been (and continue to be) made simply boggles the mind. Unless you need 50 million or more of your supplies, you won't even be hitting the break-even point.

    If you open a wall-wart up, you'll find:
    1) A transformer.
    2) A thermal fuse. This is required for safety in case the supply overheats.
    3) Rectifying diodes; usually a pair.
    Sometimes you may also find a capacitor. Some wall-wart supplies actually are regulated, but most are not; they just supply the specified voltage at the specified current.

    We're not kidding you, nor making fun of you, or anything like that.

    The 7812 regulator you found is a voltage regulator that's not usually included in "wall-wart" supplies. Most things powered by wall-warts either don't need regulation (like fans, for instance) or contain their own regulation circuitry.

    I spelled out components you'd need (in addition to the 7812 regulator that you already knew about) along with approximate costs (not including shipping) to build a regulated 12v power supply. A regulated power supply will cost more than an unregulated power supply.

    You must use a transformer to isolate your circuit from the mains power, otherwise it would be unsafe. As long as a transformer is required for safety, you may as well use it to reduce the line voltage to near the required voltage. A couple of inexpensive rectifiers or a rectifier bridge changes the AC into rippled DC. After that, everything is fine tuning.
     
  15. t06afre

    AAC Fanatic!

    May 11, 2009
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    People here are only trying to help. And they have given you the correct answers. Yes you can build it your self. But you can never beat large scale production. Besides every thing connected to the mains should be CE or UL approved. Most of the people in this forum do small/medium electronic projects at home as a hobby, that will say just for fun and recreation. You can not put a price tag on that. I like to go fishing, but not because I need food. Of course I like to have friends over and serve them a meal made of mountain trout catched by my self. But I would rather not think about how much this meal cost me in mony. But the adventure in catching the fish is worth all the mony:rolleyes:
     
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