LED light set up?

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LED light set up?

Unread post #1 by balarila » Wed Nov 26, 2014 12:15 pm

For my entry to the Dremel contest, I plan to put some battery powered LED lights in lieu of a candle.

Got a battery holder, some hookup wire, soldering lead, and 4 10 mm LEDs. The lady at DEECO says I should put a 1 kOhm, 1/4W resistor in series to protect the bulbs. Though I can't understand why since she says the bulbs are rated at 3V and I am using two AAA batteries.

They are, however, out of 1kOhm resistors.

Can I just put two bulbs in series to achieve the same lowering of voltage on the bulbs?

My high school electronics is a little rusty. Been some time.
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Re: LED light set up?

Unread post #2 by joey81 » Wed Nov 26, 2014 12:38 pm

Voltage isn't much of a problem. Its the electric current. Too much current will fry your LED.
The resistor is to limit the current.

Using the water analogy: voltage is to pressure, while resistor is to the valve.

I think. Hehehe.
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Re: LED light set up?

Unread post #3 by balarila » Wed Nov 26, 2014 12:55 pm

Good analogy. Also current is to flow, or Q, as we call it in water. We also call pressure as H (which, I think, came from head).

Tried lighting up each LED with two AA battery pack and they seemed to light up OK and didn't get warm. You think this'll be good without the resistor then?

If I need a resistor, should I put the resistor in parallel to all the bulbs or should I put it in series with the bulbs (which are in parallel)?

Which circuit?

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Re: LED light set up?

Unread post #4 by joey81 » Wed Nov 26, 2014 1:46 pm

Should be series.
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Re: LED light set up?

Unread post #5 by ynos » Thu Nov 27, 2014 2:49 pm

The voltage of LEDs differ per color.

Red, Orange, Yellow - 1.8-2.2v / 24mA
Green, Blue, White, Warm White, Pink - 3.0-3.4v /24mA

I suggest to put the resistor in series as well. If you put them in parallel, if one of the LED goes out, it would take small amount of time to destroy the other LEDs due to over voltage/current.

You might also want to check this website - http://ledcalc.com/
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Re: LED light set up?

Unread post #6 by balarila » Thu Nov 27, 2014 10:10 pm

ynos wrote:The voltage of LEDs differ per color.

Red, Orange, Yellow - 1.8-2.2v / 24mA
Green, Blue, White, Warm White, Pink - 3.0-3.4v /24mA

I suggest to put the resistor in series as well. If you put them in parallel, if one of the LED goes out, it would take small amount of time to destroy the other LEDs due to over voltage/current.

You might also want to check this website - http://ledcalc.com/


Thanks. Problem is, the LEDs I got has no rating at all. It's one of those LEDs that slowly change color. The lady in DEECO says it's rated at 3 volts. But another lady there says I should connect a 1kOhm, 1/4W resistor.

Since I have it connected to two 1.5V batteries, do I still need a resistor?
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