what is the voltage across R252 & R253. Please do the needful asap. Thanks in advance!!

Discussion in 'Homework Help' started by veeresh540, Dec 17, 2014.

  1. veeresh540

    Thread Starter New Member

    Dec 17, 2014
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    Hi,
    I need to calculate voltage across R252 & R253.please help me in getting through it. Thanks in advance :)
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    hi,
    For two series resistors, Vjunc = Vin * Rtop/[Rtop +Rbot] ,assuming the junction is not loaded with another resistance.

    Is this Homework.?
     
  3. veeresh540

    Thread Starter New Member

    Dec 17, 2014
    13
    0
    Hi,
    Thanks for the quick response. Its required for my project. So,I need the voltage values across them in order to verify with mine. Please do the needful!!
     
  4. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    hi,
    Using the formula I posted, what do you calculate the voltage to be.? lets see your answer.;)
    E
     
  5. veeresh540

    Thread Starter New Member

    Dec 17, 2014
    13
    0
    hi,
    For R252, V=5/11v
    For R253, V=50/11v

    Am i right?
     
  6. veeresh540

    Thread Starter New Member

    Dec 17, 2014
    13
    0
    hi,
    across 252 - 0.45V flows
    across 253 - 4.55v flows
    Am i right?
    Please do reply asap..
     
  7. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    Hi.
    Vout = Vin * 100k/[100k+10k] , so Vo = 5v * [100k/110k], = 5v * 0.909' = 4.54' Volts.

    This of course assumes the ON pin has a very high input impedance [ resistance]

    Does this help.?
    E
     
  8. veeresh540

    Thread Starter New Member

    Dec 17, 2014
    13
    0
    hi,
    Voltage at the R252 is 5V only right. The circuit acts as voltage divider and we will get voltage divider output at the R253 and after the resistor R252.
    So for calculating the power dissipation of R252 we should consider the voltage passing through the R252.
    We will get potential divider output after R252.

    Is my analysis right?? Please clarify me!!
     
  9. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
    2,503
    380
    hi,
    The current thru the 10K and 100K in series is 5v/110k is 45 micro amps!
    So the voltage drop across the 10K is, 0.000045 *10,000 = 0.45'v and the 100k is 0.000045*100,000 = 4.54'v

    Dissipation 10k = 0.000045 * 0.45 = 20 micro Watt and the 100k= 0.000045 * 4.54 = 204 micro Watts

    BTW:
    the voltage passing is incorrect, the voltage is across a resistor, the current 'passes' , flows thru a resistor.
     
  10. vishal12345

    New Member

    Dec 16, 2014
    8
    1

    first get the difference between these two protocol here
    it will clear your basics i think

    http://www.firmcodes.com/difference-rs-232-rs-422-rs-485/
     
  11. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,802
    832
    He is not referring to communications protocols.
    R252 and R253 are the labels for two different resistors on his schematic.
    They are not the names of any protocols.
    I doubt the link you provided would be useful.
     
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