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Powering 12V dc fan from AC?

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  • 03-10-2011 1:46am
    #1
    theTinker
    Closed Accounts Posts: 638 ✭✭✭


    I wish to power a 12V DC car fan from my home socket.

    Could an eletrical person advise me on how to do this?

    I know i cannot directly wire a DC motor to AC power.
    However, all the adapters i can buy easily seem to output tiny amount of amps rather than the large amount required by a fan 10+.

    Does anyone know the best way i can do this? What i need to buy?
    I can DIY something together if needed.

    I'd like a cheap option please! its a budget project.

    Is there like 12V batteries that i can also plug in so it recharges while powering?

    Thanks in advance. Any help is welcome.


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    #2
    DublinDilbert
    Registered Users Posts: 5,379 ✭✭✭DublinDilbert


    theTinker wrote: »
    I wish to power a 12V DC car fan from my home socket.

    Could an eletrical person advise me on how to do this?

    I know i cannot directly wire a DC motor to AC power.
    However, all the adapters i can buy easily seem to output tiny amount of amps rather than the large amount required by a fan 10+.

    Does anyone know the best way i can do this? What i need to buy?
    I can DIY something together if needed.

    I'd like a cheap option please! its a budget project.

    Is there like 12V batteries that i can also plug in so it recharges while powering?

    Thanks in advance. Any help is welcome.

    What size is your DC fan? how many amps does it take? how long do you want to run it for? how long will it be turned off for?

    You could charge up a car battery (or even a 12V alarm battery) from a mains charger, then use this battery to supply the fan. Or you could just run the Fan from a 12V DC power supply, but it would be one big power supply, as I would guess the fan takes 20A or so. The likes of maplin would probably have a 20A DC power supply, but it won't be cheap.


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    #3
    theTinker
    Closed Accounts Posts: 638 ✭✭✭theTinker


    DublinDilbert wrote: »
    What size is your DC fan? how many amps does it take? how long do you want to run it for? how long will it be turned off for?

    You could charge up a car battery (or even a 12V alarm battery) from a mains charger, then use this battery to supply the fan. Or you could just run the Fan from a 12V DC power supply, but it would be one big power supply, as I would guess the fan takes 20A or so. The likes of maplin would probably have a 20A DC power supply, but it won't be cheap.

    Its about 16inch circumference. I dunno how many amps it takes, Its from a car and seems to require alot of amps at start up then alot less when in motion. This seems to be true of all fans.
    I'd want to run it for most of the day or at least whenever I want. So a constant power supply is needed.


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    #4
    xtract
    Closed Accounts Posts: 1 ✭xtract


    Car fans may not be designed to run continuously , maybe something like one of these would be better in the long run ?

    http://www.jebbtools.ie/Search/extractor


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    #5
    indie armada
    Registered Users Posts: 834 ✭✭✭indie armada


    you could buy a 12v dc psu in peats or maplins. we used to use them to run cb's and two way radios in the house years ago. they go from 2 amp up to 15 amp so all ye need to do is find out how much ampage it will use and buy your psu accordingly.
    http://www.peatswholesale.ie/REGULATED-13.8V-DC-POWER-SUPPLY.html


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    #6
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    theTinker wrote: »
    Its about 16inch circumference. I dunno how many amps it takes, Its from a car and seems to require alot of amps at start up then alot less when in motion. This seems to be true of all fans.
    I'd want to run it for most of the day or at least whenever I want. So a constant power supply is needed.

    Yea its all motors that take a high current on starting, unless started with soft starters etc. Imagine force holding the motor stopped, it would take 5 or 6 times its full load current. Well at the instant of starting, the motor is stopped, so it takes a high current that rapidly reduces once it is in fact able to start.

    DC permanent magnet motors generate an emf in the opposite direction to the supply current direction, so as it speeds up, its reverse or back emf increases, reducing the current it takes, the faster it goes.

    It can not go fast enough for this back emf to equal the supply voltage, or there would now be no current flow to power it, something similar to an AC indiction motor not quite able to reach synchronous speed. So as the workload on a motor increases, it slows, and so its current draw increases.

    It would take probably 10 to 20 amps, on the average car, and it is possible they might not be great for continous use as said already in another post.


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