DIY Network

All Projects

TV Projects

    What Do You Want To Work On?

      What Activity Do You Want To Do?

        0

        Available Projects

        Get Results

        DIY Network /

        Message Boards

            DIY Message Boards  Hop To Forum Categories  Home Improvement  Hop To Forums  Electrical    Undervoltage in DC computer Fan
        Go
        New
        Find
        Notify
        Tools
        Reply
          
        Undervoltage in DC computer Fan Sign In/Join 
        posted
        I have a computer fan that I want to use in a ventilation project. The fan will run off an AC to DC adapter. The problem is that the fan is too loud and too powerful. The fan is 12v, .35a, can I safely run it off a 6v, .40a or higher AC to DC converter in order to slow it down? Or will doing that risk overheating and/or damage to the fan? Thanks.
         
        Posts: 3 | Registered: Aug 02, 2014Reply With QuoteReport This Post
        Picture of Jaybee
        posted Hide Post
        I know how easy it is to gt caught up in using something that you already have but sometimes it's just not worth the trouble.

        Simple fans, under $30:

        http://www.lowes.com/Search=du...true&Ntt=duct+fans#!


        Jaybee
         
        Posts: 10477 | Location: Knoxville, Tennessee | Registered: Sep 27, 2003Reply With QuoteReport This Post
        posted Hide Post
        the fan will be fine as long as it spins fast enough to move air. it won't move much, as in "why try," unless you get up to 8 or 9 volts for a 12 volt fan. at that point, you can feel a breeze without the nasty whine.

        larger fans can be had that run at lower speeds for the same amount of air pushed. a surplus parts type store would be a good place to look without paying full price.

        the little round desktop fans in a cage from Target are also very quiet and move a goodly amount of air. I have two of the 5-inchers at work in case of a/c failure, and they do the trick.

        This message has been edited. Last edited by: swschrad,


        sig: if this is a new economy, how come they still want my old-fashioned money?
         
        Posts: 5849 | Location: North Burbs, MN | Registered: Mar 14, 2007Reply With QuoteReport This Post
        posted Hide Post
        I appreciate the help, but the suggestions won't work for my project. I'm gonna have to use a computer/case fan for numerous reasons.

        I hooked up and tested the 120mm computer fan to a 6v 400ma DC adapter (it was for charging batteries for those Power Wheels driveable toy cars) and it works pretty well. The fan is now quieter and it's still moving a lot of air. Ideally, I'd like to have something that moves less air. I'm still not sure if it's safe to power that fan off the 6v 400ma adapter though.

        I have many choices, it's just a matter of figuring out what will work best (fan size, speed, noise level, etc.). It would be nice if someone could tell me if it's safe to power the 12v .35a DC fan off the 6v 400ma DC adapter long-term (constantly running all day and night)?

        This message has been edited. Last edited by: blu78,
         
        Posts: 3 | Registered: Aug 02, 2014Reply With QuoteReport This Post
        posted Hide Post
        well, when you find out, let us know Wink

        here's what is in those fans. you have a little DC fan motor, it's a multi-magnet no-commutator job. that means there is a chip inside with a little oscillator that does the job of turning the magnets on and off in sequence to make the motor turn the fan blade. below some voltage, the fan won't spin, so at that point the current will remain in one magnet, and over time could burn it out. if the fan is moving air, it should be sufficient to cool the circuit and magnets.

        fans with a third lead, usually white or grey, will also have a magnet and pickup coil that generates a relative tachometer signal voltage indicating how fast the thing spins, this is used to send alarms if it slows down (bearings drying/dying) or stops (circuit failure.)

        in this application, the tach would be interpreted by external circuitry as always in failure, but I suspect if there is air movement, the insides will be OK. life may even be extended if there is no dust pulled across the fan in the airflow to gum the bearings, as the bearing lube is not likely to break down.

        specifications for these fans at the manufacturer websites only deal with the fans operated at design conditions, including mean expected hours of life. so figuring that is going to be purely experimental. everybody who has hacked down fan noise with lower voltage never sets up that experiment with multiple units and consistent monitoring, it's really just a hack.

        This message has been edited. Last edited by: swschrad,


        sig: if this is a new economy, how come they still want my old-fashioned money?
         
        Posts: 5849 | Location: North Burbs, MN | Registered: Mar 14, 2007Reply With QuoteReport This Post
          Powered by Social Strata  
         

            DIY Message Boards  Hop To Forum Categories  Home Improvement  Hop To Forums  Electrical    Undervoltage in DC computer Fan

        © Scripps Networks 2009

        Advertisement

        Posting Guidelines

        • Please be sure posts are category appropriate.
        • No off-topic or off-color postings.
        • Postings may be deleted at the discretion of DIY moderators.
        • No advertising is allowed.
        • Be nice. No name calling, personal attacks or flaming.
        • Certain words will trigger moderation of the post. These words mostly cover political or religious topics, which are OFF the topics covered by DIY.

        Full Guidelines

        For general message board help, click the tab labeled "Tools," and choose "Help" from the dropdown menu.