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Questions about led Answered

hi!

1 :trying to find out if there are any  problem (caused by the red leds lower forward voltage) or not to drive blue and red leds with the same driver when connected in series. 

2: if you drive  blue or  red led with lower capacity than rated (ex 2w instead of 3w) could that affect the wavelength for resp color

could a red 660nm become a 630nm?

the questions concern a growth lightsource

thanks















Tags:led

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0
kristerh
kristerh

7 years ago

ok,

so i drop that idea then ,

Did not know there was constant current driver with dimmer, have only seen the old transformer type


Ok , one last question for know that i have been thinking of,

when leds are rated at 3w ... where does that number come from?

my theory is that for 3w @ 700ma blue it would be ~3,4x0,7= 2,38w
and red 3w ~2,2x0,7= 1,54w

Am i missunderstanding something with the calculations?

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mpilchfamily
mpilchfamily

Reply 7 years ago

Yes wattage = voltage times current. Don't calculate the specs of the LED. Actually find the spec sheet and know what the forward voltage and current ratings are.

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Kiteman
Kiteman

7 years ago

It is the nature of an LED that they only ever produce a single wavelength of light, no matter what their power.

LEDs that give out variable colours are actually combinations of red, blue and green LEDs in the same housing, with them being switched on for different amounts of time.

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kristerh
kristerh

Reply 7 years ago

Thanks for answer!

So here comes the next question,

If you want to reduce power to led arrays , could you run 15x3w with a 10x3w driver?

If your driver is rated 10x3w-700ma and you run 15x3w ,
would the power be reduces about 30% , so the same 700ma becomes more like a 500ma driver?

that is of course if your voltage is in the specified range , which it still could be when using the lower voltage red led

If this idea is plain stupid , then i want to know how people do when they say they run a constant current powered lightsource at 70% power

thanks

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steveastrouk
steveastrouk

Reply 7 years ago

no you can't do it by increasing the number of lights, you need a dimmable driver

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Kiteman
Kiteman

Reply 7 years ago

Argh, stepping out of my zone now, we'll see what others recommend, but it may be something like pulsing the LEDs so that they are only actually on for 70% of the time, but flickering so quickly that what we see is not a series of flashes, but a dimmer light.

Pulse width modulation?