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How to wire up this LED? Answered

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Hello there,

I've bought this cluster of red LED's from Maplins and I'm unsure how I should go about making a circuit that lights them up using a 9 volt battery. (I also have a simple switch).

The forward voltage of the LED is 2.5v and the forward current is 30mA. According to my calculations I would need to put a 1/2W or greater 220 ohm resistor in the circuit. Is this correct?Also how do I go about wiring the cluster up as they are in fact 6 individual led's. Do I need a resistor for each?

My knowledge of electric circuits is limited.

Many thanks,

Julian



5 Replies

user
iceng (author)2013-03-03

Wire it three LEDs in series with a 50 ohm resistor as two sets going 
to your 9 volts.

3 × 2.5 = 7.5 volts
A resistor needs to drop 1.5 V  / .030 A  ==>  50 ohms.

A

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user
Joachimanderson (author)iceng2013-03-05

Brilliant! Many thanks for your advice. Going to try this this evening.

Many thanks,

Julian

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user
iceng (author)Joachimanderson2013-03-05

Great, if it works 4 U.
I hope you mark the best answer :)

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user
frollard (author)2013-03-03

I can't make out exactly what that circuit diagram you attached says. It looks like some of the leds are in series and others are in parallel - not knowing how they are hooked up internally we can't suggest what you need. If they are all individual LEDs with their own legs its very easy:

1) Do not use 9v batteries. They are expensive and their total energy storage is crap. Get a AA or AAA battery holder - it will pay for itself after one or two replacements. Preferably use rechargable AA's.
4xAA = 6V
6xAA = 9V
2) Use a series/parallel resistor calculator to figure out what circuit to make. http://led.linear1.org/led.wiz
9volts, 6 leds, 30mA, 2.5V each
leaves 2 strands of 3 leds in series with a 56 ohm resistor on each strand (also in series). The 2 strands are then connected to the power source in parallel.

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Joachimanderson (author)frollard2013-03-05

Thanks for your help and advice. Got myself an AA battery holder and try out your circuit. I think the Led's are all individually mounted within the light.

Many thanks,


Julian

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