LED wiring. Help!

[Gordon Gekko]

I'm working on a project that is going to require about 6-8 LED's and I can't quite get the wiring correct.

I am using a cannibalized book light which originally had one 5mm LED powered by 3 LR44 button cells. I have been able to reconfigure it anyway I want and it works fine - until I try to add a second LED inline. Then, no worky. I have made sure to connect the posts in the correct manner and even flipped them to make sure, tried 3mm etc, but nothing. What am I doing wrong? Any help appreciated.

Mods - this is prop related and not OT. I will be adding more info about the prop once I get this mystery solved. Thanks

 

[kimncris]

<div class='quotetop'>(Jmtwo @ Nov 15 2006, 05:54 PM) [snapback]1358487[/snapback]</div>

I'm working on a project that is going to require about 6-8 LED's and I can't quite get the wiring correct.

I am using a cannibalized book light which originally had one 5mm LED powered by 3 LR44 button cells. I have been able to reconfigure it anyway I want and it works fine - until I try to add a second LED inline. Then, no worky. I have made sure to connect the posts in the correct manner and even flipped them to make sure, tried 3mm etc, but nothing. What am I doing wrong? Any help appreciated.

Mods - this is prop related and not OT. I will be adding more info about the prop once I get this mystery solved. Thanks
[/b]

you've verified that the second one works by itself?

I have a diagram on my website of a project with multiple leds
and you can see the breadboard too

http://kimncris.com/tutorials/Neuralyzer.php

maybe it will help ?

-cris

 

[Gordon Gekko]

I actually did check the second LED to make sure it worked.

Your diagram fit the bill and solved my problem. :thumbsup Thanks Cris.

 

[kimncris]

no problem- glad that thing could be of use to someone...

ck

 

[Great_Bizarro]

Just a reminder, when you add leds in series "daisy chained" -0-0-0- the amperage remains the same and the voltage drops. When you add leds in paralell =0=0=0= the voltage stays the same and the amperage drops.

 

[Gordon Gekko]

So if I wire 8 5mm LED in parallel, how fast would that drain 3 LR44 batteries?

 

[Great_Bizarro]

There are a lot of variables there. What is the (total) ma. draw of the leds, what is the (total) amp hours (ma hours?) of the batteries. Add the first ones up and devide the 2nd one by it and you get a general idea.

 

[jackdoud]

<div class='quotetop'>(Jmtwo @ Nov 16 2006, 10:04 AM) [snapback]1358805[/snapback]</div>

So if I wire 8 5mm LED in parallel, how fast would that drain 3 LR44 batteries?
[/b]

Will they be on continuously, blink, or only light on command? What color are they? 8 LEDs will drain button cells pretty quick, you'll only get optimum brightness for a few minuites but the LEDs should show modest light for a few hours. Green LEDs will seem brighter longer than blue LEDs due to the human eye's propensity towards green light. Bigger batteries would be better but it really depends on what your trying to do.

 

[exoray]

<div class='quotetop'>(Jmtwo @ Nov 16 2006, 09:04 AM) [snapback]1358805[/snapback]</div>

So if I wire 8 5mm LED in parallel, how fast would that drain 3 LR44 batteries?
[/b]

First off I believe the internal resistance of the LR44 batteries will not allow you to pull that much current, if I remember correctly you can only pull out about 30mA (maybe 40mA) out of them at once that's all they have to give... And that might be enough to run 2-3 REGULAR LEDs (probably only one blue, white or superbright) in parallel... But, lets assume you can pull as much as the 8 LEDs need...

Regular yellow, green, red LEDs maybe 1 hour...

White or Blue or Superbright maybe 30 minutes...

Just guesses without the actual specs of the LEDs

The LR44 batteries average about 120 mAh or so they claim you probably only get 75-100 mAh in the real world...

Regular LEDs draw about 15-20 mA @ 2-2.5 volts

White, Blue and Superbright LEDs draw about 20-30 mA @ 3-3.5 volts