noob question

Discussion in 'General Electronics Chat' started by adamclark, Nov 5, 2013.

Oct 4, 2013
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ok,, Ive looked around and cant seem to find a simple down to earth explanation for it... What difference does the color of an led make to the voltage/current? It seems that red leds needs less power/current than a green or yellow one, but it seems that the blue ones are more sensitive than all of them...

2. wayneh Expert

Sep 9, 2010
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3,246
It's related to the chemistry used and the fact that higher frequency (lower wavelength) photons carry more energy and require a higher voltage to shake them loose.

See here.

PackratKing likes this.

Oct 4, 2013
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good response,, however the noob and simple down to earth explanation were not achieved..lol..I just don't understand the wavelength thing.. Im in the mobile audio video industry and from ive learned in the past 3 months of building circuits and trying to learn my understanding of frequency is totally different than the electronics side of frequency.. hell and wavelength for that matter.. I completely understand the audio side of freq. and wavelength but the electronics side is so different that I have a hard time understanding.. but I kinda get it a little bit.. So the red LED has a lower freq. than other colors so its more stable and varying voltage and current? or does voltage even matter? from what ive learned and experienced its the current that hurts the LEDS more over than the voltage,, I mean I know that if you throw 12 volts at any LED without a resistor that its toast immediately.. but ive been able to put 7 volts to a red LED without a resistor and it worked without issue, but I put the same 7 volts to a yellow one and it didn't even blink before it burnt out..

Aug 17, 2013
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It has to do with physics more than anything else. As I understand it, this is the simplified version: when an electron in an atom receives enough energy to jump to a higher orbit it emits a photon (light); the higher the energy, the higher the orbit and the higher the frequency of the photon (the electromagnetic radiation -aka light-). So, Blue needs more energy than green and yellow, and green and yellow need more energy than red.

Does it make any sense?

Oct 4, 2013
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Oh,,, That makes perfect sense to me really.. I kinda understand whats going on with it... Thanks for dumming yourself down for me...

Aug 17, 2013
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I didn't.

That's as much as I know about the subject.

Last edited: Nov 6, 2013
7. wayneh Expert

Sep 9, 2010
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3,246
I think you're getting it. Blue or UV photons carry more energy than red or IR ones, so it takes more energy (voltage) to emit them.

8. crutschow Expert

Mar 14, 2008
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The visible spectrum goes from 400nm (blue) to 700nm (red) in wavelength. Since photon energy is inversely proportional to wavelength (directly proportional to frequency) this means the energy required to generate blue light is nearly twice that required to generate red light.

9. Papabravo Expert

Feb 24, 2006
10,340
1,850
You have this backwards. When an electron absorbs an incoming photon of any energy it jumps to a higher quantum state (energy level). When it drops back to it's ground state it emits a photon of a given frequency(wavelength). For any photon the frequency times the wavelength is a constant. That constant is the speed of light. The other relationship (Planck's Energy formula) is that the energy is equal to Planck's constant times the wavelength.