# Save energy using LED in series.

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

1. ### nepdeep Thread Starter Active Member

Sep 14, 2011
140
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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..

Apr 16, 2011
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...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 Active Member

Sep 14, 2011
140
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its just an example...give me the reason...of my curiosity please

4. ### Shagas Active Member

May 13, 2013
802
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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 Active Member

Sep 14, 2011
140
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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

Mar 24, 2008
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8. ### ErnieM AAC Fanatic!

Apr 24, 2011
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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 Active Member

Sep 14, 2011
140
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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 Senior Member

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

Bob