house plug to 12 volts???

Discussion in 'The Projects Forum' started by aespino88, May 3, 2010.

  1. aespino88

    Thread Starter Member

    Mar 31, 2010
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    i was wondering......... is there a way to convert a 120v house plug to 12v using resistors or something?
     
  2. Bychon

    Member

    Mar 12, 2010
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    The usual way is to use a "wall wart". It plugs into the standard recepticle and provides 12 volts...DC or AC, as you wish. Just buy the one that puts out what you want. You could attach a transformer of your own choosing, but this is not something you can fit inside a plug.
     
  3. eblc1388

    Senior Member

    Nov 28, 2008
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    The most important point is that the wall wart offers you electricity safety, which resistor certainly cannot provide.

    A voltage dropper using just resistors is *dangerous* and user risks electrocution.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    And risks fire. A wall-wart is one of the devices you charge a cell phone with.

    One thing you didn't mention is if the 12v you want was AC or DC.

    Wall warts come in many flavors, so read it well to see if it is AC or DC.

    Also, most are NOT regulated. If you want regulated power, get yourself a 7812 to connect to your circuit where the power supply enters the circuit.

    http://www.datasheetcatalog.org/datasheets/150/44435_DS.pdf
     
  5. aespino88

    Thread Starter Member

    Mar 31, 2010
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    i wanted ac to dc. i have this small car amp 125.2 and i wanted to connect to a 8in subwoofer. i know car amps run off amps not voltage but i figured such a small car amp and speaker wouldn't be much of a problem. would you know of a certain wall wart that would be perfect for my situation? oh whats a 7812???
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Want are the power requirements of this amplifier?
    How many amperes does it use at full power?

    Bertus
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    No such luck with a wall-wart for the amperage you want.

    Do you have a car battery charger? That should have the juice you need.

    A car battery charger converts AC to DC and many in high enough amperage to do what you want.
     
  8. aespino88

    Thread Starter Member

    Mar 31, 2010
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    i don't know how many amps it needs, but it has a green fuse with a 15 in it. its only supposed to put out 125 watts @ 4 ohms and 250 @ 2 ohms. i don't think it would need a lot to put out such a small amount of watts.
     
  9. Bychon

    Member

    Mar 12, 2010
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    250 "small" watts at 12 volts requires over 20 amps if the amplifier is 100% efficient, and it isn't. You are free to look for a 15 or 20 amp wall wart, but I don't think you'll find one.
     
  10. aespino88

    Thread Starter Member

    Mar 31, 2010
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    how many amps are in a house plug?
    i'm not planning to put it to the max i just want to add a nice deep bass to my room.
     
  11. Bychon

    Member

    Mar 12, 2010
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    OMG! You just don't get it. You can't just put a resistor into a wall outlet and have it supply 12 volts to an amplifier. The amplifier wants 12 to 14 volts of DC. It wants to use a variable amount of current. A resistor will not vary itself in order to get the voltage to the amplifier to remain constant. If you persist in this, you will blow up the amplifeir, and maybe yourself.
     
  12. retched

    AAC Fanatic!

    Dec 5, 2009
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    You will burn your amp UP, your house DOWN or both.

    AC that comes out of the wall, is a DIFFERENT beast. the sine wave swings from -120vAC to +120vAC (ish). That causes a coming and going effect in the electron flow in the wires. (It ALTERNATES as in Alternating Current)

    Car amps use DC voltage. DC voltage from a car battery outputs a steady (non alternating, DIRECT current (From one point to another non-ALTERNATING).

    A resistor is a CURRENT component. By reducing the current, there is a voltage drop, and the rest of the power is put off as heat.

    So if you wanted to drop 120vAC to 12vAC using resistors, it would be a huge heater, glowing red, if any (especially 10 to 20amps) current flowed.

    This is how electric heaters work. The red things you see glowing are resistors.

    Now, you need DIRECT current. (battery power)

    The way to convert AC to DC is to use a RECTIFIER.

    Rectifiers are made from DIODES.

    Diodes are one-way valves for power. When the power from the wall (AC) tries to ALTERNATE, the diodes keep it from going backwards.

    So after the rectifier, you have turned AC into DC.

    BUT. You need about 13vDC (I know you said 12v, but just bear with me) not 120vDC.

    So a transformer that drops the AC voltage and can handle the current you need, will give you around 12v AC, then you can rectify it to around 12vDC.

    The problem you will face NOT using DC:

    The AMP is built to use DC, so it has no devices in it to handle backwards flowing AC.

    That backwards flow will cause many problems. resulting in HEAT (and nothing working) and possibly a fire.

    A car battery charger does what you want.

    It has a large transformer that can handle alot of CURRENT,
    It rectifies it into DC.
     
  13. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
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    Well at least he'll get one Boom from the subwoofer :)
     
  14. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Find the circuit breaker (or fuse) that controls your "house plug". You will find there are more than one "house plug" connected to that circuit breaker.

    Typically your "house plug" is wired for 15 - 20 ampere service.

    Everything plugged into that circuit does not exceed the rating of the circuit breaker (or fuse).

    That being said ... you need to buy whatever amplifier you wish to use, one that runs on the "house plug" voltage as your writings indicate your apt to do something incorrectly and cause harm to you, your family, and your family's property.
     
  15. gerty

    AAC Fanatic!

    Aug 30, 2007
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    It also needs to be filtered do that you won't have a "hum" in your music.
     
  16. retched

    AAC Fanatic!

    Dec 5, 2009
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    Yeah, dont kill yourself or family/friends.

    Use a car charger.
     
  17. bertus

    Administrator

    Apr 5, 2008
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  18. aespino88

    Thread Starter Member

    Mar 31, 2010
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    see this is exactly why i like and have respect for this forum. you guys actually take the time to explain why and why not things works. thanks alot, i have learned so much from you fellas. thanks
     
  19. SgtWookie

    Expert

    Jul 17, 2007
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