NIS6111 - Function?

Discussion in 'General Electronics Chat' started by J.Green, Sep 4, 2008.

  1. J.Green

    Thread Starter Member

    Jul 15, 2008

    I am designing an automotive circuit that will use a PIC microcontroller. The automobile may be either positive or negative ground. I'm looking for some way to make sure that +5v ends up going to the microcontroller, regardless if the car is positive or negative ground.

    I was looking for ideas on how to accomplish this and came across this IC.

    1. Will the NIS6111 work for my application? If so any suggestions on wiring it up;
    2. If the NIS6111 won't work, any suggestions on ensuring +5v at the microcontroller for either a +ve or -ve ground vechicle. I'm trying to avoid creating two separate circuits.

    Thanks for the help.
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    If it were me, I'd use a simple bridge rectifier.
  3. J.Green

    Thread Starter Member

    Jul 15, 2008
    thingmaker3: I'm familar with bridge rectifier to convert AC to DC, but how would I use one to ensure constant polarity at a given point in a circuit, when inputs could be +ve or -ve?

  4. SgtWookie


    Jul 17, 2007
    It (a rectifier bridge) works the same way with DC inputs that are connected backwards, or correct polarity.

    Besides, rectifier bridges are very cheap, and available everywhere. Why limit yourself to a particular design?
    Just use the + and - outputs of the bridge to supply your regulator voltage.
    Have the external voltage supply connected to the AC inputs of the bridge.

    Since automotive systems are (generally) at least 6.3v (for the ancient ones), you would still have enough voltage left after a bridge rectifier for a PIC. If you want to plan for such low voltage systems, you might go to the added expense of using Shottky diodes and low-dropout regulators - but that should be an "extra cost" option.

    I don't know of anyone who's made a positive earth/ground vehicle in the last 20 years or so. I don't know why anyone would do such a thing.
    Last edited: Sep 5, 2008
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    To add the SgtWookie's comment, the ones still running have been changed over to 12 volts with negative ground (the only parts that can be had require the change). Unless you have a time machine, finding a positive ground automobile is going to take some real effort.