# Need help with led circuit

#### grognak

Joined Nov 2, 2015
7
Hello everyone,

I am trying to figure out what I need to complete a project I am working on. I am trying to run 9 of these Leds http://www.amazon.com/gp/product/B0059H5YUK?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s01 from a AA battery pack for a prop I am making. I will also be adding a toggle switch. I was wondering if anyone could tell me if the resistors it comes with will work or if I will need other ones and If the system will be efficient enough to run for a little while. Im concerned that I will either burn up my leds or it will drain the batteries in 10 minutes. I know nothing about wiring leds and could really use some help designing an efficient wiring schematic so my prop will stay lit for a while. thank you everyone.

#### #12

Joined Nov 30, 2010
18,210
I was wondering if anyone could tell me if the resistors it comes with will work
Nobody can tell without the resistance rating of the resistors and how much voltage you are going to apply.

#### grognak

Joined Nov 2, 2015
7
ok, :/ Im pretty lost here but I think 2 AA batteries would be 3v correct? I know the resistors are 1/4 watt but don't know the ohms. is there any way you would be able to let me know what resistors I would need based off of 2 AAs and 9 of those leds? should I use something besides AAs?

#### Dodgydave

Joined Jun 22, 2012
9,069
Says 2v drop, probably 120 to 330 ohms resistors,

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#### mcgyvr

Joined Oct 15, 2009
5,394
They seem to be 100 ohm 2% (brown-black-black-black-red)
and the LEDs seem to be 2Vf
so (3V-2Vf)/100 = .01 Amps (or 10mA) which is perfect for long life..

So with 2 x AA batteries you need to make 9 strings of an LED and resistor in each string..

Like this.. note only 3 shown..

#### grognak

Joined Nov 2, 2015
7
thank you very much! I am still a little confused as to how to wire them together to the power supply. (sorry, this is my first electrical project and its all foreign to me) also, would the resistor go be fore the led on the positive leg or after the led on the negative? thanks again for your help.

#### mcgyvr

Joined Oct 15, 2009
5,394
thank you very much! I am still a little confused as to how to wire them together to the power supply. (sorry, this is my first electrical project and its all foreign to me) also, would the resistor go be fore the led on the positive leg or after the led on the negative? thanks again for your help.
I updated my post to show a schematic... and the resistor could be before OR after the LED.. it doesn't matter..

Think of the resistor as a "water valve"... It doesn't matter where it goes as it "sets the pace (sets the current)" for the whole garden hose.. The water (current) can only flow as fast as the valve allows it in the whole circuit.

#### grognak

Joined Nov 2, 2015
7
just refreshed and saw the diagram you made. thank you so much! I think I can figure that out youre the best

#### grognak

Joined Nov 2, 2015
7
if I wanted to add a toggle switch in line I would do it on the positive leg correct?

#### mcgyvr

Joined Oct 15, 2009
5,394
if I wanted to add a toggle switch in line I would do it on the positive leg correct?
That would be "recommended" but in this situation it really doesn't matter..
But its usually always safest to disconnect the "non-grounded" connection.

#### grognak

Joined Nov 2, 2015
7
That would be "recommended" but in this situation it really doesn't matter..
But its usually always safest to disconnect the "non-grounded" connection.

Thank you!

#### grognak

Joined Nov 2, 2015
7
out of curiosity, how bright do you think the leds will shine in this setup?

#### blocco a spirale

Joined Jun 18, 2008
1,546
out of curiosity, how bright do you think the leds will shine in this setup?
Compared to what? My guess is that they won't be as bright as the sun.

#### ian field

Joined Oct 27, 2012
6,539
Hello everyone,

I am trying to figure out what I need to complete a project I am working on. I am trying to run 9 of these Leds http://www.amazon.com/gp/product/B0059H5YUK?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s01 from a AA battery pack for a prop I am making. I will also be adding a toggle switch. I was wondering if anyone could tell me if the resistors it comes with will work or if I will need other ones and If the system will be efficient enough to run for a little while. Im concerned that I will either burn up my leds or it will drain the batteries in 10 minutes. I know nothing about wiring leds and could really use some help designing an efficient wiring schematic so my prop will stay lit for a while. thank you everyone.
This might help:-

http://www.talkingelectronics.com/projects/30 LED Projects/30 LED Projects.html