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Topic: LED driver shield (Read 7110 times)previous topic - next topic

redtop03

Apr 21, 2013, 08:27 pm
I'm still in the planning stages of building an aquarium controller using the Arduino Mega 2560....

http://www.ledsee.com/index.php/new-products/arduino-6-channel-led-shield-035-07-1a-detail

I plan to use an external 24v 15a 350w power supply to power the LEDs...

can this be used with a series of 8 x 3w high power LEDs ?

according to the specs for the shield,current is selectable between 0.35a , 0.7a , and 1amp...

if I use 500ma LEDs,can I add 2 strings of 8 x 3w LEDs per channel providing I don't exceed the amperage of the 24v power supply ?

muddy

#1
Apr 22, 2013, 03:46 pm
Do you have 8 separate leds? Or 8 connected in series?

Do you have more specifications on these leds? Like voltage? I assume the current per led is 1A (since it's 3W).

You can not connect 2 strings to 1 channel.

Chagrin

#2
Apr 22, 2013, 04:57 pm

This is a buck driver so input voltage must be greater than the forward voltage of the LEDs.

The maximum current through each driver is determined by a sense resistor. They appear to have solder jumpers to enable different combinations of resistors that are already present on the board.

You can't have strings of LEDs in parallel connected to this or any driver; they will not balance current. Each string must be individually current limited.

One string of 8 * 3W LEDs at 500ma suggests individual LEDs with a forward voltage of 6 volts, and 8 LEDs in series would be 48V. That's greater than your 24V supply and over the 30V limit of the driver. You should also post a link to the LEDs you're using for more accurate advice on what would be possible.

redtop03

#3
Apr 23, 2013, 12:54 am
sorry guys,I didn't really know what I was doing or how to ask for help,the LEDs that I plan to use are Bridgelux

royal blue
Wavelength: 452-455nm
Forward voltage: 3.6V @700mA
Max. current: 700mA

white
Color temperature: 6500-7000K
Forward voltage: 3.7V @700mA
Lumens: 180-200 lm
Max. current: 700mA

I thought these were 3v each,I see now that I can only use 6 per driver channel,and I plan to connect the LEDs in series.....

from what I've read about some LED drivers,I assumed that if you have a driver that ran at 1000ma you could connect 2 strings of 500ma LEDs and it would split the 1000ma current between the 2 strings....

I've never did anything with LEDs before so I'm still trying to learn...I don't think this driver shield is gonna be enough for my needs,looks like 36 LEDs will be the max I could use without stacking about 4 of those shields...I appreciate the help

Chagrin

#4
Apr 23, 2013, 05:01 am
from what I've read about some LED drivers,I assumed that if you have a driver that ran at 1000ma you could connect 2 strings of 500ma LEDs and it would split the 1000ma current between the 2 strings....

Exact opposite. Very difficult to balance current between two strings of LEDs in parallel; heat, age, etc. will throw off the balance and/or it will just be generally unstable.

You must be trying to run a massive heap of LEDs. You should try looking for an AC-powered driver, but going that route you won't be able to dim them (well, the cheap ones are typically not dimmable). Then again if you have that many LEDs you could turn them on and off in groups (relay board/shield, etc.) for the same effect.

redtop03

#5
Apr 23, 2013, 12:31 pm

from what I've read about some LED drivers,I assumed that if you have a driver that ran at 1000ma you could connect 2 strings of 500ma LEDs and it would split the 1000ma current between the 2 strings....

Exact opposite. Very difficult to balance current between two strings of LEDs in parallel; heat, age, etc. will throw off the balance and/or it will just be generally unstable.

You must be trying to run a massive heap of LEDs. You should try looking for an AC-powered driver, but going that route you won't be able to dim them (well, the cheap ones are typically not dimmable). Then again if you have that many LEDs you could turn them on and off in groups (relay board/shield, etc.) for the same effect.

I will need between 100 to 150 3w LEDs for a 360 gallon aquarium reef tank,I've found a few different drivers that will serve my needs and work with the Arduino but after seeing this shield,I thought it could simplify my build a great deal....

I'll look into the AC LEDs as well....I really want the dimming feature of the Arduino and the power efficiency of LEDs....currently,I use six 250w metal halide lights for illumination but there's never more than 2 at a time on,I have them connected to a controller that turns 'em on in a series to kinda mimic the sun moving across the tank but the tank looks odd partially lit

thank you for the suggestions and help,I'm still learning about LEDs and still have a lot to learn,and I appreciate all the help I can get

#6
Apr 23, 2013, 12:33 pm

I've never did anything with LEDs before so I'm still trying to learn...I don't think this driver shield is gonna be enough for my needs,looks like 36 LEDs will be the max I could use without stacking about 4 of those shields...I appreciate the help

Your setup with this shield should put out  at least 4000 lumens ( the blue LEDs usually have a lot less output than the white LEDs). That is extremely bright! No need to stack 4 of those together!
If you really need more lumen output you can also try to find LEDs that run at 1A max instead of the 700mA as these should have a higher lumen output.
http://trippylighting.com

http://ledshield.wordpress.com/

#7
Apr 23, 2013, 01:00 pm
That is quite a massive tank!
It looks like you are trying to directly compare the lumen output of a metal Hali lamp with the lumen output of LEDs. Traditional lamps, including metal halide, distribute their light ove a much steradian, thus the need for large reflectors to collect all that light.
LEDs distribute their light much more dictional and with appropriate TIR optics are able to direct their light output with much higher optical efficiency. So light output per steradian - light density - is more important than overall lumen output.
http://trippylighting.com

http://ledshield.wordpress.com/

redtop03

#8
Apr 23, 2013, 01:49 pm

That is quite a massive tank!
It looks like you are trying to directly compare the lumen output of a metal Hali lamp with the lumen output of LEDs. Traditional lamps, including metal halide, distribute their light ove a much steradian, thus the need for large reflectors to collect all that light.
LEDs distribute their light much more dictional and with appropriate TIR optics are able to direct their light output with much higher optical efficiency. So light output per steradian - light density - is more important than overall lumen output.

yep,really large tank I built myself

yes,I want equal to or greater than the light output of the halides with LEDs...I understand that the LEDs are better focused therefor waste less of their usable illumination,produce much less heat and much cheaper on the monthly power bill

problem is,I don't have a way of measuring lighting PAR to accurately know how many LEDs I will need,and I really don't want to invest in a \$600 light meter that I'd likely never use again LOL so I'm kinda copying from other large reef tank owners,I at least have an idea where to start....

my thought is to remove 1 or 2 halides and build an LED array that looks close to what the remaining halides output is then turn them down,I know that's not a great way to do things LOL

I'm really happy with the color temperature and light output of the halides that I'm using now and I'm not going to LEDs because I think they will grow coral better or are a better source of light,I've got to reduce my power consumption or get rid of my tank LOL

thank you all for the replies and great suggestions,it's all really appreciated

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