Led questions

[Jstdv8]

I've gotta guy who is going to build me a dimmable fixture.
I'm having trouble with a few things.

1. How many 3w Cree bulbs do I need for sps for a 120g 4' tank?
Rapid led sells a kit for 90 gallon and a kit for a 125. Not sure which kit to try and emulate. I've only got a couple sps currently under 6 bulb t-5 with ati bulbs

2. He do I make the dimming come on slowly? How is it connected and what controls it?

Thanks in advance
Justin

 

[Jstdv8]

Bump,
Any advice would be great. I'm trying to order this soon.
Thanks :beer:

 

[mcgyvr]

The "generic" formula is
watts = (L" of tank x W" of tank / 22) x 3 for non-sps tanks
and
watts = (L" of tank x W" of tank / 18) x 3 for sps tanks

and dimming depends on the drivers you use and the "controller" you have..The typical 3 options are
1. analog 1-10V
2. PWM 0-10V (or 0-5V PWM)
3. 0-100k resistance

Manual dimming (by turning a knob) is done with options 1 or 3
Automatic dimming with a controller is done with options 1 or 2
If you want automatic then you need some sort of controller (reef controllers have dimming options or function specific LED dimming controllers).
And before you buy any drivers or controllers you MUST pick a dimming option and they must match

example.. my reef angel reef controller has PWM dimming outputs that attach to my meanwell LED drivers that support PWM dimming.

 

[Jstdv8]

Mcguvr,
Thanks for the reply.
That's about what I thought for LEDs, I was thinking 72 and that came to 69
You have me concerned about the controller. If this guy builds me something but its not compatible with my controller would it be better to buy a compatible controller or change drivers? I'm assuming the drivers are changeable. I know very little about them though. I have a rke I've never installed.
Do you happen to know if that will work to make a true dimming and brightening and not just on and off?
Thanks again,
Justin

 

[Jstdv8]

Also, the guy is considering making two fixtures with about 55 LEDs each. While this is overkill is there any downside to having too many lights? I can always just dim them down to achieve what I need I'm thinking