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Newbie: LED power consumption question

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cocoadev

New Member
I want to build a large bright LED VU Meter. I know very little about electronics and decided the best thing for me would be to buy a kit that i could modify...

With this kit http://www.hobbytron.net/vk4304.html the LED's are too dim. If I were to replace the LED'd with say this... http://www.superbrightleds.com/leds/b_specs.htm

...would it actualy be brighter? would the circuit be able to handle it? would i blow a component? if it could not handle it, would using the LED ouputs to trigger relays be a viable option?

Thanks very much for any help,

regards,

ben
 

coyotesden

New Member
re:Brighter leds:

Brighter leds do consume more power, I'd be carefull,...The brighter the LED the more current is needed.
 

ukeee

New Member
You could replace the standard LEDs with superbright LEDs however you need to chose your replacement LEDs carefully. Look for an LED with a forward current of 20mA the LED you mentioned has but it also has a forward voltage of 3.5V to 5V, this may upset your circuit standard LEDs are usually around 2 - 2.3V. You should be able to find an LED meeting these requirements.

f
 

cocoadev

New Member
So what are the odd's that sticking the LED's I mentioned into the kit would work? If it's a fair gamble I might just risk putting them in and seeing what happens.

Or is that just silly?!

thanks again for your help.
 

Gandledorf

New Member
Sticking in the brighter LED's should be fine. An LED only sucks down what power is available to it, and even an ultrabright which normally takes more, if put on a lower power resistor, will only suck down as much power as it is given.

Remember, V = IR, so lets assume for a moment that your power supply is @ 5V, and your current LED's want 20mA. Assuming a 2.2V drop over the LED, we have 2.8V/20mA = 140ohms. So there are probably something on the order of a 150ohm resistors in series with your LED's to limit the current. Given that a higher power LED has a larger forward voltage drop, you probably need to snip out the current resistor and stick in a new one. Using the LED you suggested, you need a smaller resistor, something on the order of 70ohms.
 

cocoadev

New Member
Gandledorf said:
Sticking in the brighter LED's should be fine. An LED only sucks down what power is available to it, and even an ultrabright which normally takes more, if put on a lower power resistor, will only suck down as much power as it is given.

Remember, V = IR, so lets assume for a moment that your power supply is @ 5V, and your current LED's want 20mA. Assuming a 2.2V drop over the LED, we have 2.8V/20mA = 140ohms. So there are probably something on the order of a 150ohm resistors in series with your LED's to limit the current. Given that a higher power LED has a larger forward voltage drop, you probably need to snip out the current resistor and stick in a new one. Using the LED you suggested, you need a smaller resistor, something on the order of 70ohms.
That makes sense, thank you very much and everyone else.

ben
 
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