DIY LEDs - The write-up

[Jimmy54]

So could someone do a quick write up with the formulas to determine how many LEDs a particular driver could handle? (or point me to the info)

I will give it a shot (excuse my english)

Dividing the output voltage of a specific driver by the Vf(foreward voltage) of an LED, will tell us how many LEDs we can have in a string.
e.g: a driver has an output voltage of 48V and the Vf of a specific LED is 3.3V, this will give us 48/3.3= 14.5.
We're not gonna round this up to 15 - although some people do - I'd rather stay on the save side and leave some headroom by rounding it down to 14.
So we could have 14 LEDs in a string. An LED with Vf 3.6 makes 48/3.6=13.3 which means 13 LEDs in a string.

The output current tells us how many parellel strings a specific driver can handle (if you want to go that way)
When a LED is rated for 1000mA max, you could drive it at that current (it's not recommended because of its lifespan, but you could)
So when a driver has an output of 3.9A - which is the same as 3900mA - then 3900/1000= 3.9 strings.
In this case we can round up that number to 4 strings fed with 3900mA ...
3900mA /4= 975mA ... so all the LEDs will be driven at approx 975mA.

Now, if we want to drive the same LEDs at around 700mA , to extend the lifespan and create less heat, we simply divide 3900 by 700 which is 5.5 strings.
In this case rounding up to 6 would drive the LEDs @ 3900/6= 650mA, and rounding down to 5 strings would be 3900/5= 780mA.

This is pretty much all there is to it.

Hope it makes sense

 

[brassmonkyballs]

Just want to be clear before I place this order. The HLG-185-48B will dim all the way to zero/no light/completely off?

The HLGs only dim down to 10% but it is very linear dimming with no dead spots. I posted this info yesterday based on the 120 i am running and the spec sheets.

Have to use the main power on a switch/timer for on-off. If you're trying to use a controller to dim to off incorporating a relay back to the mains may do the trick if you can find one with the right specs I suppose. Kcress or anybody have any ideas on that?

 

[bamf25]

I got a 10v dc supply and it a plug connection on it. Is it ok to just cut this off then figure out pos vs negative on the wires, or should I take the exctra step to put in a dc plug adapter on my dimmer circut. My dimmer is already working off a 9 V battery as I was waiting to recieve the 10 v adpator? If I just cut the adaptor off is there any easy way (ratehr than trial and error) to now what is pos or neg.

Another interesting idea. I do not have 10 v dimming on my Apex Lite, may add the dimmer in the furture. Considering potential surge issues, could I just have the eln's always on, then plug the 10v into the power strip for the Apex? So when the switch turns on it is really just turning on the dimemr circut (I know it would require 2 10v supplies to make it work).

 

[Gold Stripe]

Have to use the main power on a switch/timer for on-off. If you're trying to use a controller to dim to off incorporating a relay back to the mains may do the trick if you can find one with the right specs I suppose. Kcress or anybody have any ideas on that?

I can cut power to the HLGs by having them plugged into one of the controller's power bars after they have been dimmed down to 0% by the controller. I just wanted to make sure nobbody had experienced any issues with powering them back up while the controller still has them dimmed all the way down at 0%.

 

[TheFishMan65]

brassmonkyballs, what happens when you go below 1 volts. Is zero volts any dimmer? The datasheet doesn't really say.

bamf25, no problem cutting the connector. It may make dissassembly harder. If they go off by shutting of the 10v that should be fine. You may waste some electricity.

 

[brassmonkyballs]

brassmonkyballs, what happens when you go below 1 volts. Is zero volts any dimmer? The datasheet doesn't really say.

bamf25, no problem cutting the connector. It may make dissassembly harder. If they go off by shutting of the 10v that should be fine. You may waste some electricity.

Fishman...no difference between zero volts and 1V and if we are to believe the specs thats 10% So I'm wondering if a relay with a 1VDC control input could be used to close the mains from the dimmer... if one wanted to dim to zero the relay would open the mains below 1vdc....with the right relay it might throttle the inrush too when it closed...not that I think its an issue here. I'm not real up to speed on relays though and putting the mains on a timer is easiest. Meanwell actually suggests the relay too. I only use the dimming for color mixing anyhow and not sunrise/set scenarios.

What I wonder is if using the resistor method what happens below 10k ohms...I needed 0-10V to control the ELN I'm running RBs off of so I just used the same source for the HLG dimmer. Maybe I'll swap out for a 100k ohm pot and see if there's a difference.....so much to try, so little time...and probably won't make a difference.....

 

[kcress]

I will give it a shot (excuse my english)

Dividing the output voltage of a specific driver by the Vf(foreward voltage) of an LED, will tell us how many LEDs we can have in a string.
e.g: a driver has an output voltage of 48V and the Vf of a specific LED is 3.3V, this will give us 48/3.3= 14.5.
We're not gonna round this up to 15 - although some people do - I'd rather stay on the save side and leave some headroom by rounding it down to 14.
So we could have 14 LEDs in a string. An LED with Vf 3.6 makes 48/3.6=13.3 which means 13 LEDs in a string.

The output current tells us how many parellel strings a specific driver can handle (if you want to go that way)
When a LED is rated for 1000mA max, you could drive it at that current (it's not recommended because of its lifespan, but you could)
So when a driver has an output of 3.9A - which is the same as 3900mA - then 3900/1000= 3.9 strings.
In this case we can round up that number to 4 strings fed with 3900mA ...
3900mA /4= 975mA ... so all the LEDs will be driven at approx 975mA.

Now, if we want to drive the same LEDs at around 700mA , to extend the lifespan and create less heat, we simply divide 3900 by 700 which is 5.5 strings.
In this case rounding up to 6 would drive the LEDs @ 3900/6= 650mA, and rounding down to 5 strings would be 3900/5= 780mA.

This is pretty much all there is to it.

Hope it makes sense

Very well stated.

 

[kcress]

So I'm wondering if a relay with a 1VDC control input could be used to close the mains from the dimmer... if one wanted to dim to zero the relay would open the mains below 1vdc....with the right relay it might throttle the inrush too when it closed...

I can't see that working directly. There are almost no relays that run at 1V and if there are they'd want a bunch of mA to run them. Most of these analog outputs don't have the chops to run anything more than an electronic input. And lastly if that 1V relay was subjected to 10V it would surely let all of its smoke out.

 

[Blackhawk007]

Thanks for the info Blackhawk...would love to give it a try. Any idea how soon is soon?

Not sure but initially it was only expected to be a few months. They are having trouble with moisture getting into the cans and have not resolved this. I'll toss ya a PM when I get some.

 

[brassmonkyballs]

I can't see that working directly. There are almost no relays that run at 1V and if there are they'd want a bunch of mA to run them. Most of these analog outputs don't have the chops to run anything more than an electronic input. And lastly if that 1V relay was subjected to 10V it would surely let all of its smoke out.

makes sense...and we surely don't want anything letting all of its smoke out

 

[brassmonkyballs]

Not sure but initially it was only expected to be a few months. They are having trouble with moisture getting into the cans and have not resolved this. I'll toss ya a PM when I get some.

appreciate it!

 

[jeffreylam1132]

Subscribe!

 

[Raven1645]

I want to make a LED system on my not yet built tank, but I just don't get them...
Some people have 24 3ws, others have 84, on a same type of tank...

Is there anyone who could help me determine the right type and amount of leds?
My tank will be 250 cm long and 60 high, with lots of anemones.

If possible please shoot me a PM.

 

[TheFishMan65]

Raven go to my home page and find the LED summary. It will answer the basic questions. Then come back with any you still have.

 

[katchupoy]

maybe i can help...

maybe i can help...

I want to make a LED system on my not yet built tank, but I just don't get them...
Some people have 24 3ws, others have 84, on a same type of tank...

Is there anyone who could help me determine the right type and amount of leds?
My tank will be 250 cm long and 60 high, with lots of anemones.

If possible please shoot me a PM.

Raven for some reason your pm does not work???

 

[ramrunner]

im taking the dive to leds i would also like to know after reading many many many and so on post no one talks much about alge with leds aka hair sino also i cant find the link to the LED summary thanks

 

[katchupoy]

im taking the dive to leds i would also like to know after reading many many many and so on post no one talks much about alge with leds aka hair sino also i cant find the link to the LED summary thanks

In my setup/experience, I have less. I believe this due to the less shifting spectrum of LEDs (time will tell). But it also boils down to reef up keeping and not to be blame on the lighting alone.

 

[ramrunner]

true but i put my vhos on for summer to drop heat from 2 400 w hqi mh on my 90 gal tank with in 2 weeks i could mow it if i put a scoop on my lawn mower the idea of not needing my chiller is also encouraging

 

[Raven1645]

Thanks to you both for your help, both threads helped alot!

I'm now planning to have 96 3w leds total, 48 40-50lm blue and 48 120-150lm white, 4 rows of 24 leds.
This will go across the 250 cm of my tank.
Would this be sufficient?
I could also do 2 rows of 48 or 3 rows of 32 leds, ofcourse. Or if it's really needed I can always go with more leds.
And what optics would I need? I've seen both 60 and 90 degrees and I don't know which would be best. Also, the site where they sell the leds say viewing angle 120 degrees, does this mean there's already a lens on it?

Thanks!

 

[Raven1645]

Another thing:
The leds I found are 3.6V each, but all power supplies seem to be 12V, how does that work?