resistor on top of each other....?

Discussion in 'General Electronics Chat' started by supermankid, Jul 21, 2014.

  1. supermankid

    Thread Starter Member

    May 26, 2013
    Why is the resistor placed one on top of other...instead of using a separate voltage divider from the battery to compare the voltage....this resistor one on top of other just makes it look more complex and complex for calculation too....
    Is there a special reason....a hidden trick in this circuit....I don't see the meaning of just complicating(besides saving...3 resistors)....

    FYI: MAX8214
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    it is a voltage devider. just has a lot of taps probably a adc (analog to digital converter) why would you want individual voltage devders? it sis a voltage devider ladder.
    supermankid likes this.
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    Its a voltage ladder,each junction has a different voltage going lower from top to bottom,so that each comparator switches on as the battery voltage decreases,it uses less resistors than your conversion.
    supermankid likes this.
  4. crutschow


    Mar 14, 2008
    By my count it save one resistor, but that's the reason it's preferred. Never use more components then you have too, especially just to simply a calculation.

    To simplify the calculation of the string and avoid having to solve any simultaneous equations, you can start out by deciding what current you want through the network (it looks like about 7 microamps for the network shown). Then calculate the resistor values to give each of the desired trip-point voltages for 7 microamps through each resistor starting from the bottom and going to the top. That way you only have to solve one or two simple equations for each resistor value.
    supermankid likes this.
  5. MrChips


    Oct 2, 2009
    Because if you use n voltage dividers you will have severe non-linearity and possible non-monotonicity.

    Using a ladder network reduces the non-linearity.
    supermankid likes this.
  6. NorthGuy

    Active Member

    Jun 28, 2014
    For n-tap ladder you need n+1 resistors. For n individual dividers you need 2n resistors. So you save 2n - (n+1) = n-1 resistors.
    supermankid and ErnieM like this.
  7. wayneh


    Sep 9, 2010
    Personally, I find the ladder simpler to understand, draw and build as well. To my eye, it's not more complicated, just the opposite. One glance and you see all the reference voltages at once. And it's not just numerical, the ladder arrangement actually gives a graphical cue about how the reference voltages are related.
    supermankid likes this.