Sequential switching (12v dc)

Discussion in 'The Projects Forum' started by philll48, Nov 24, 2011.

  1. philll48

    Thread Starter New Member

    Nov 24, 2011
    i would like some help in my old age
    i am working a project that needs 12v dc to be switched sequentially to different relays
    i dont know much about electronics and so i am looking for something i dont even know if it exist
    thx for your help
    i will probably be using a car battery so it will have some amps
    dont know if that makes a difference
    also i will be using some kind of proximity switch

    phil v
  2. SgtWookie


    Jul 17, 2007
    Hello Phil,
    Welcome to AAC.

    Perhaps you can describe your project more completely? This frequently results in a much easier and/or less expensive solution than originally proposed.

    Relays are generally considered pretty power-hungry; there are more efficient ways to switch power on and off.

    There are advantages in that 12v relays can be purchased fairly cheaply at an auto parts store - IF the load is also powered by 12v.

    I'll caution you that automotive batteries are a poor choice for deep-cycle use such as this will be. They're designed to blast out 200A-500A for perhaps as much as 30 seconds, and then be immediately charged back up completely. They can do this because they have LOTS of very thin plates, where deep-cycle batteries have fewer and much more thick plates.

    If you try to use auto batteries in a deep-cycle application, the battery plates will quickly fall apart, and the battery will be scrap. Even one deep discharge cycle can do permanent damage.

    Back to your problem statement - if your application is all 12v DC, I could see using a CMOS 555 timer to clock (a) 4017 Johnson counter(s) (these have 8,9, or 10 usable outputs depending on how you're using them) whos' outputs are controlling the gates of N-channel enhancement mode power MOSFETs to switch the ground side of the loads.

    This kind of a set-up doesn't require many parts. If you need more than 10 outputs, it gets a bit more complicated, but still do-able.