Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

AC Adapter

  1. Dec 20, 2007 #1

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If I have a device from the UK, and on its AC adapter, it says that on 'sec' (presumably referring to the secondary winding of the transformer), the output is as follows:

    12 V
    1500 mA
    18VA

    My question is as follows...if I don't have an adapter for the UK style plug at this moment (or a transformer to provide the proper 230 V AC), and I don't want to try and get a North American-style AC adapter from the company that manufactures the device just yet, then would the following be a possibility? If I manage to dig up an AC adapter that has the same output on the DC side as this one, is it safe to just USE it with the device?

    My reasoning is that if the voltage is the same, presumably all of the ICs etc will be happy...they'll be getting the correct Vcc's or Vss's or whatever the hell they need. As for the current, I am assuming that the 1500 mA is an upper limit on the current that CAN be supplied by the AC adapter based on the power that is going in. That would suggest to me that as long as the output current on my scavenged AC adapter is less than or equal to 1500 mA, then I'll be ok. The device may not quite be getting enough power to make it work, but it will be safe. On the other hand, I am assuming that if the current limit on my scavenged AC adapter is higher than 1500 mA, then it will be unsafe, because it will then be *possible* for the device to draw more current that it would be able to if connected using the manufacturer's AC adapter.

    But am I wrong? Have I got things the other way around? Is the 1500 mA NOT an upper limit after all?
     
    Last edited: Dec 20, 2007
  2. jcsd
  3. Dec 21, 2007 #2

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    1500 mA is the maximum amount of current that the adapter can deliver. The device may therefore use as much as 1500 mA, since the manufacturer of the device chose to sell it with an adapter that can deliver 1500 mA. You need to replace it with an adapter that is capable of delivering at least 1500 mA.

    The device may not need the entire 1500 mA that the adapter can supply, but it might, and you won't know without additional testing or information. Under no circumstances will it need more than 1500 mA.

    - Warren
     
  4. Dec 21, 2007 #3

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Right ok. I understand that. It sounds like you are saying that even if I supply it with an adapter than can provide more than 1500 mA, the device will probably never actually draw more than that much current. And it's better to supply it with more than enough power than it needs to work properly, rather than less (because in that case it simply won't work at all).
     
  5. Dec 21, 2007 #4
    yup sounds right. i've had device from the us brought to other places and the adapter only takes in 120vac and puts out 9v dc. just take that off, throw in the local adapter that puts out 9v dc and as long it can deliver sufficient current it works
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: AC Adapter
  1. AC to DC wall adapter (Replies: 5)

  2. AC ADAPTER for Forklifts (Replies: 10)

Loading...