Voltage divider confusion...

Discussion in 'Homework Help' started by Average Drinkability, Nov 28, 2012.

  1. Average Drinkability

    Thread Starter New Member

    Mar 27, 2012
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    Directly from part of an assignment in my microcontrollers class: "...implement a voltage-divider circuit using 4 resisters [sic] (all with the same resistance) in series between +5V and ground. This circuit wil provide nodes with voltage levels of 3.75 V, 2.5 V, and 1.25 V..."

    How is this even possible?? 3.75 + 2.5 + 1.25 is two and a half volts more than 5, not to mention 4 resistors of equal resistance in series will all have the same voltage... I only need to use the lower two anyway so I'd probably be better off ignoring this spec and building my own circuit.
     
  2. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Take a look at this:

    [​IMG]

    The Vout is not the voltage drop across a single resistor, it is the voltage drop between the top connected resistor and ground. If you have the output set after the top resistor, it means you're adding the voltage drops of the bottom three, which is 3.75v. If you have it after the second, it means you're measuring the voltage drop across the bottom two resistors, and if you measure it right above the last resistor, you're only measuring the voltage drop across that last one.

    Does this help, or should I draw a diagram related to your problem?

    Regards,
    Matt
     
    Average Drinkability likes this.
  3. Average Drinkability

    Thread Starter New Member

    Mar 27, 2012
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    Ohh thank you! I was only looking at it as drops across individual resistors, not from the node to ground. This is exactly what I needed.
     
  4. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Glad to hear it! :) So you're all set then?
     
  5. Average Drinkability

    Thread Starter New Member

    Mar 27, 2012
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    Yes, everything else is all software and controller hardware setup, I appreciate the help!
     
  6. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Come back any time :)
     
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