Save energy using LED in series.

Discussion in 'General Electronics Chat' started by nepdeep, Jun 10, 2013.

  1. nepdeep

    Thread Starter Member

    Sep 14, 2011
    139
    0
    Hi I have the LEDs set up in circuit as follows: Very simple series and parallel. Now what I assumed is that the LEDs need 20mA current to give max light.
    My question is .....if they are in series the two leds consume same current to give maximum brightness....if they are in parallel the two leds consume twice as much the current in series....so my analogy is that the battery lasts for longer time in series LEDs but the amount of brightness..for both the circuit is the same...pleas throw me some light if I am missing something..
    IMG_0704 (Medium).JPG
     
  2. hexreader

    Active Member

    Apr 16, 2011
    250
    82
    Your thinking is correct...

    ...Minor practical correction .... I have not come across LEDs that drop 1 Volt. 1.6 Volts might be typical for a red LED. Other colours of LED typically have higher voltage drop.
     
  3. nepdeep

    Thread Starter Member

    Sep 14, 2011
    139
    0

    its just an example...give me the reason...of my curiosity please
     
  4. Shagas

    Active Member

    May 13, 2013
    802
    74
    What you are missing is the following :
    LED's have a forward voltage drop (minimum voltage required to turn on those LEDs) which is anywhere from 1,6-3,4 depending on the LED colour but usually around 2,4 Volts so let's use that number for the example .
    If you connect 2 of those in series then you will need at least 4,8 volts and 20 ma .
    If you connect them in parallel then you will only need 2,4 volts but 40 ma.
    Power spent is Voltage x current so in both cases you are spending 96 mW.
    (this is just theoretical as I didn't include resistances etc.)
     
  5. Shagas

    Active Member

    May 13, 2013
    802
    74
    reason for what? the voltage drop?
     
  6. nepdeep

    Thread Starter Member

    Sep 14, 2011
    139
    0
    Ya where is the power lost in resistance? If we include resistance too my statement is correct. If u dont agree please show one calculation for suport. Thanks in advance
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    Ya whare is dat?

    Turns out you are 100% correct, if you run them off a battery or any fixed voltage the series connection takes less power then the parallel connection.

    Seems Shagas correctly calculated to power each LED uses, but not the total power needed to drive them (led plus resistor power).

    One devil of a detail is you need enough voltage to run both in series. Two 2.4V leds in series need more then 5V to drive them since you need to waste some power in the resistor to set the current.
     
  9. nepdeep

    Thread Starter Member

    Sep 14, 2011
    139
    0
    Thanks! :) Hi senior members. Could some experienced brain support or deny my assumption please ? I just dont mean I am right but Where am I wrong I am wrong.
     
  10. BobTPH

    Active Member

    Jun 5, 2013
    782
    114
    Several people have already told you that you are not wrong. Why do you keep asking where you are wrong?

    Bob
     
Loading...