Too much light?

Lildingy

New member
I built a small acrylic hood and diy leds on a fuval spec 2 gal

The lights are 1@ 10w 10k and 1@10w 445k do you think i wemt overboard? I have no dimming capability atm at it was kinda am experment
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kcress

New member
Yes. Too bright.

You might be able to run the two LEDs in parallel and cut the current they use in half. That would get it down to about the right level.

Normally you don't want dissimilar LEDs in parallel but it might work depending on the throw of the dice. The good point is that since these LEDs can handle one of your drivers alone if these LEDs don't balance well nothing will be hurt.
 

muda

New member
I am afraid you will be getting very dis balanced color spectrum when using kcresses advice. But sure it wont hurt trying.
Easyest way is to buy lesser amperage drivers IMHO.
 

cfredallen

New member
Even if the drivers don't have a dimming circuit they should have a current adjustment pot internally that you should be able to turn down to make them less bright. It may not have enough adjustment but it could help.

Sent from my PC36100 using Tapatalk 2
 

Dapg8gt

New member
You can shade the output of the lights by using some plastic window screen or eggcrate.. Untill you figure out if you can add a potentiometer to dim your drivers. Just put two layers of screen under the lights.. Run a test not installed on the tank to make sure the beam from the lights doesn't melt the screen. I read stories of guys burning the table or floor with LEDs directly on them left on for only a few mins. Good luck.
 

Lildingy

New member
Thank you guys for all your help, i think i may try with a frag offa my purple acro to test before i do anything else to it. One question as i am a complete noob here, in paralell i would be hookin both hots to the driver and both negatives to the driver?

Ok so o reread that, how or is there some kinda caculator to figure out what size rezistor to put in it? Say drop it from 900ma to say 700 ma ?
 
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kcress

New member
I did not get your parallel question. You may need to rephrase it...

As for resistors for fixed dimming there is no "table" but if you can tell us what current you are running now and the actual voltage across each emitter we can do some math and tell you what resistors to get.
 

Lildingy

New member
sorry for not paying more attention to ohms law in school, the specs ond the driver state:

output 10w
output current 900ma (<± 5%)
output voltage 7-12v

do i need to check the voltage with a multimeter with the led atached?

again ty for your help and patience

with the mulitmeter i read 8.95 volts across the euroblock when the led was turned on. that was the 10k on the blue it was the exact same
 
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Lildingy

New member
ok i did some math and i am possibly way off but it seems i would need a 2k resistor to drop it down to 700ma? I am not an EE by anymeans and based my math on a long lost knowledge of high school

but here it goes please harass me if i butchered it

8.95/900=.00994
8.95/700=.01278

difference being .00264

did i tear it up?
 
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kcress

New member
If those two measure exactly the same, then you should definitely try running both LEDs in parallel on the same driver. Especially since you have everything terminal blocked. See what you think. That will still be a heck of a lot of light for that tank.

As for shunt resistors:

I don't know what your math was... :)

You have a current source. that will supply 900mA thru whatever load it's driving. The resistor's duty is to pass 200mA if you want to reduce the current that would otherwise pass thru the LEDs.

8.95V / 0.200A = 44.75 ohms

This resistor dropping 200mA will dissipate:
0.200A x 0.200A x 44.75 ohms = 1.79Watts. Make sure this resistor is rated at 5watts or more of power dissipation.

Caveats. Since this shunt resistor will cause less current to flow thru the LED the operating point will be different which means the voltage will be different which would change the resistor value a little. The result is you will need to adjust the resistor a little from the computed value above.

Use a resistor like this:
http://www.digikey.com/product-detail/en/AVT25-50-10%/AVT25-50-ND/257624

Set it to about 44 ohms then measure its resistance. Install it across the emitter. Power up. Measure the voltage across the resistor and using ohms law compute the current thru it. If you don't like the result POWER OFF and then re-adjust then power back on. Step and repeat. NOT following this procedure may likely blow your emitters.
 

Lildingy

New member
Thank you so very much Kcress for your time and wealth of knowledge :) If all else fails I have a 14gal Biocube that needs lights :)
 

Lildingy

New member
Ok I feel like a dumb***, I guess the math is a little above my paygrade:( I was hopping i could get a say 50ohm resistor and just plug it in, but that would be way to easy :p
 
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