Connect with us

Advice for 12v dc fan switch

Discussion in 'General Electronics Discussion' started by mrbojanglesrocks, Mar 11, 2014.

Scroll to continue with content
  1. mrbojanglesrocks


    Mar 11, 2014
    Hi there, new to this site. Hope I can get some advice for a home made stir plate. I'm using a standard 12v dc fan from an old pc, gluing two round magnets on the top which will make the stir bar spin in a flask. Question is, what kind of dc adapter to use. I have a pile from old electronics but I don't want to burn out the motor or worse, cause a fire. A 9v dc 300ma adapter worked fine but not sure what the long term effects would be. Any advice would be greatly appreciated.
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to our forum.
    Running a 12 V fan from a 9 V source should be fine. It will run at less than max. speed, but if that's o.k. with your setup, go ahead. As for the current I cannot answer, lacking information. Can you measure the current frawn by the fan at 9 V? As long as it is below the 300 mA rating of your adapter, it's fine. If the fan draws more current, it is the adapter, not the fan that will burn out in the long run. You'd then need a more powerful adapter.

    Note that current drawn by the motor will rise once you put the stirrer into operation under load. Therefore measure current under load (stirrer in liquid, preferably not water but something with higher viscosity, e.g. oil).
    Last edited: Mar 11, 2014
  3. mrbojanglesrocks


    Mar 11, 2014
    Thanks for the reply. I'll check with the volt meter tonight. Is there an optimum voltage or milliamp for a 12v dc fan? I've just heard stories by using the wrong voltage drawing more current and burning things out.
  4. kpatz


    Feb 24, 2014
    The optimum voltage for a 12V fan is 12V.

    The current draw will depend on the fan. Some draw more current than others. Usually the current at 12V is printed on the fan label. The current will be higher at startup and if the fan is loaded down (by the magnet/stirrer), so take that into account as well.

    If you power it with a lower voltage like 9V it'll spin slower and draw less current. It also won't have as much torque to turn your stirrer. Test it under load to see if it's going to work before making it a permanent setup. Most PC fans don't pull much torque.
    Last edited: Mar 11, 2014
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day